Bitmask-based change tracking (#3945)

* start updating tests

* start implementing bitmask-based change tracking (#1943)

* oops

* fix some await block stuff

* slots

* reactive declarations

* component bindings etc

* start fixing slots

* fix store value invalidations

* slot stuff

* fixes

* fix

* fixes

* fix some slot stuff

* fix some invalidations

* fix if blocks

* fix a test

* destructuring in lets

* fix shadowing

* fix if block case

* all runtime tests passinfg

* almost all tests passing

* update tests

* never hoist writable vars in dev mode, fix debug statements

* beef up shadowing test

* always use renderer.reference

* fix sourcemaps

* ugh so close

* all tests passing. phase one complete, i guess

* add test for component with more than 31 dynamic values

* stable sort

* stable sort that preserves order

* linting

* failing test for bitmask overflow

* ok i think this is it

* lint

* rename changed to dirty, for more internal consistency

* update tests

* use bitwise comparison

* add comments... sort of

* update tests

* moar comments

* I don't know what happened to these tests

.eslintrc.js

@@ -35,12 +35,7 @@ module.exports = {
 				argsIgnorePattern: '^_'
 			}
 		],
-		'@typescript-eslint/no-object-literal-type-assertion': [
-			'error',
-			{
-				allowAsParameter: true
-			}
-		],
+		'@typescript-eslint/no-object-literal-type-assertion': 'off',
 		'@typescript-eslint/no-unused-vars': 'off'
 	},
 	globals: {

package-lock.json

@@ -500,9 +500,9 @@
       "dev": true
     },
     "code-red": {
-      "version": "0.0.25",
-      "resolved": "https://registry.npmjs.org/code-red/-/code-red-0.0.25.tgz",
-      "integrity": "sha512-KxR5fi6hN3Lhg/VFBaucVaWe5LT8HvgKE7+q09ZV73PbBuuLWSK8DKeOtZTbpZ41BLimaggzawSgK7HQr+m1DA==",
+      "version": "0.0.26",
+      "resolved": "https://registry.npmjs.org/code-red/-/code-red-0.0.26.tgz",
+      "integrity": "sha512-W4t68vk3xJjmkbuAKfEtaj7E+K82BtV+A4VjBlxHA6gDoSLc+sTB643JdJMSk27vpp5iEqHFuGnHieQGy/GmUQ==",
       "dev": true,
       "requires": {
         "acorn": "^7.1.0",

package.json

@@ -64,7 +64,7 @@
     "acorn": "^7.1.0",
     "agadoo": "^1.1.0",
     "c8": "^5.0.1",
-    "code-red": "0.0.25",
+    "code-red": "0.0.26",
     "codecov": "^3.5.0",
     "css-tree": "1.0.0-alpha22",
     "eslint": "^6.3.0",

src/compiler/compile/Component.ts

@@ -209,7 +209,6 @@ export default class Component {
 			});
 
 			const subscribable_name = name.slice(1);
-			this.add_reference(subscribable_name);
 
 			const variable = this.var_lookup.get(subscribable_name);
 			if (variable) variable.subscribable = true;
@@ -889,50 +888,6 @@ export default class Component {
 		return null;
 	}
 
-	invalidate(name, value?) {
-		const variable = this.var_lookup.get(name);
-
-		if (variable && (variable.subscribable && (variable.reassigned || variable.export_name))) {
-			return x`${`$$subscribe_${name}`}($$invalidate('${name}', ${value || name}))`;
-		}
-
-		if (name[0] === '$' && name[1] !== '$') {
-			return x`${name.slice(1)}.set(${value || name})`;
-		}
-
-		if (
-			variable &&
-			!variable.referenced &&
-			!variable.is_reactive_dependency &&
-			!variable.export_name &&
-			!name.startsWith('$$')
-		) {
-			return value || name;
-		}
-
-		if (value) {
-			return x`$$invalidate('${name}', ${value})`;
-		}
-
-		// if this is a reactive declaration, invalidate dependencies recursively
-		const deps = new Set([name]);
-
-		deps.forEach(name => {
-			const reactive_declarations = this.reactive_declarations.filter(x =>
-				x.assignees.has(name)
-			);
-			reactive_declarations.forEach(declaration => {
-				declaration.dependencies.forEach(name => {
-					deps.add(name);
-				});
-			});
-		});
-
-		return Array.from(deps)
-			.map(n => x`$$invalidate('${n}', ${n})`)
-			.reduce((lhs, rhs) => x`${lhs}, ${rhs}}`);
-	}
-
 	rewrite_props(get_insert: (variable: Var) => Node[]) {
 		if (!this.ast.instance) return;
 
@@ -1054,6 +1009,10 @@ export default class Component {
 					if (!d.init) return false;
 					if (d.init.type !== 'Literal') return false;
 
+					// everything except const values can be changed by e.g. svelte devtools
+					// which means we can't hoist it
+					if (node.kind !== 'const' && this.compile_options.dev) return false;
+
 					const { name } = d.id as Identifier;
 
 					const v = this.var_lookup.get(name);
@@ -1325,25 +1284,6 @@ export default class Component {
 		});
 	}
 
-	qualify(name) {
-		if (name === `$$props`) return x`#ctx.$$props`;
-
-		let [head, ...tail] = name.split('.');
-
-		const variable = this.var_lookup.get(head);
-
-		if (variable) {
-			this.add_reference(name); // TODO we can probably remove most other occurrences of this
-
-			if (!variable.hoistable) {
-				tail.unshift(head);
-				head = '#ctx';
-			}
-		}
-
-		return [head, ...tail].reduce((lhs, rhs) => x`${lhs}.${rhs}`);
-	}
-
 	warn_if_undefined(name: string, node, template_scope: TemplateScope) {
 		if (name[0] === '$') {
 			if (name === '$' || name[1] === '$' && name !== '$$props') {

src/compiler/compile/nodes/Action.ts

@@ -14,7 +14,7 @@ export default class Action extends Node {
 		component.warn_if_undefined(info.name, info, scope);
 
 		this.name = info.name;
-		component.qualify(info.name);
+		component.add_reference(info.name.split('.')[0]);
 
 		this.expression = info.expression
 			? new Expression(component, this, scope, info.expression)

src/compiler/compile/nodes/Animation.ts

@@ -13,7 +13,7 @@ export default class Animation extends Node {
 		component.warn_if_undefined(info.name, info, scope);
 
 		this.name = info.name;
-		component.qualify(info.name);
+		component.add_reference(info.name.split('.')[0]);
 
 		if (parent.animation) {
 			component.error(this, {

src/compiler/compile/nodes/Transition.ts

@@ -15,7 +15,7 @@ export default class Transition extends Node {
 		component.warn_if_undefined(info.name, info, scope);
 
 		this.name = info.name;
-		component.qualify(info.name);
+		component.add_reference(info.name.split('.')[0]);
 
 		this.directive = info.intro && info.outro ? 'transition' : info.intro ? 'in' : 'out';
 		this.is_local = info.modifiers.includes('local');

src/compiler/compile/nodes/shared/Expression.ts

@@ -9,9 +9,9 @@ import TemplateScope from './TemplateScope';
 import get_object from '../../utils/get_object';
 import Block from '../../render_dom/Block';
 import is_dynamic from '../../render_dom/wrappers/shared/is_dynamic';
-import { x, b, p } from 'code-red';
-import { invalidate } from '../../utils/invalidate';
-import { Node, FunctionExpression } from 'estree';
+import { b } from 'code-red';
+import { invalidate } from '../../render_dom/invalidate';
+import { Node, FunctionExpression, Identifier } from 'estree';
 import { TemplateNode } from '../../../interfaces';
 
 type Owner = Wrapper | TemplateNode;
@@ -213,7 +213,8 @@ export default class Expression {
 							component.add_reference(name); // TODO is this redundant/misplaced?
 						}
 					} else if (is_contextual(component, template_scope, name)) {
-						this.replace(x`#ctx.${node}`);
+						const reference = block.renderer.reference(node);
+						this.replace(reference);
 					}
 
 					this.skip();
@@ -260,42 +261,38 @@ export default class Expression {
 						// function can be hoisted inside the component init
 						component.partly_hoisted.push(declaration);
 
-						this.replace(x`#ctx.${id}` as any);
-
-						component.add_var({
-							name: id.name,
-							internal: true,
-							referenced: true
-						});
+						block.renderer.add_to_context(id.name);
+						this.replace(block.renderer.reference(id));
 					}
 
 					else {
 						// we need a combo block/init recipe
-						(node as FunctionExpression).params.unshift({
-							type: 'ObjectPattern',
-							properties: Array.from(contextual_dependencies).map(name => p`${name}` as any)
-						});
+						const deps = Array.from(contextual_dependencies);
+
+						(node as FunctionExpression).params = [
+							...deps.map(name => ({ type: 'Identifier', name } as Identifier)),
+							...(node as FunctionExpression).params
+						];
+
+						const context_args = deps.map(name => block.renderer.reference(name));
 
 						component.partly_hoisted.push(declaration);
 
-						this.replace(id as any);
+						block.renderer.add_to_context(id.name);
+						const callee = block.renderer.reference(id);
 
-						component.add_var({
-							name: id.name,
-							internal: true,
-							referenced: true
-						});
+						this.replace(id as any);
 
 						if ((node as FunctionExpression).params.length > 0) {
 							declarations.push(b`
 								function ${id}(...args) {
-									return #ctx.${id}(#ctx, ...args);
+									return ${callee}(${context_args}, ...args);
 								}
 							`);
 						} else {
 							declarations.push(b`
 								function ${id}() {
-									return #ctx.${id}(#ctx);
+									return ${callee}(${context_args});
 								}
 							`);
 						}
@@ -329,7 +326,7 @@ export default class Expression {
 						}
 					});
 
-					this.replace(invalidate(component, scope, node, traced));
+					this.replace(invalidate(block.renderer, scope, node, traced));
 				}
 			}
 		});

src/compiler/compile/render_dom/Block.ts

@@ -1,7 +1,7 @@
 import Renderer from './Renderer';
 import Wrapper from './wrappers/shared/Wrapper';
 import { b, x } from 'code-red';
-import { Node, Identifier } from 'estree';
+import { Node, Identifier, ArrayPattern } from 'estree';
 import { is_head } from './wrappers/shared/is_head';
 
 export interface BlockOptions {
@@ -34,7 +34,7 @@ export default class Block {
 	key: Identifier;
 	first: Identifier;
 
-	dependencies: Set<string>;
+	dependencies: Set<string> = new Set();
 
 	bindings: Map<string, {
 		object: Identifier;
@@ -90,8 +90,6 @@ export default class Block {
 		this.key = options.key;
 		this.first = null;
 
-		this.dependencies = new Set();
-
 		this.bindings = options.bindings;
 
 		this.chunks = {
@@ -302,7 +300,13 @@ export default class Block {
 				properties.update = noop;
 			} else {
 				const ctx = this.maintain_context ? x`#new_ctx` : x`#ctx`;
-				properties.update = x`function #update(#changed, ${ctx}) {
+
+				let dirty: Identifier | ArrayPattern = { type: 'Identifier', name: '#dirty' };
+				if (!this.renderer.context_overflow && !this.parent) {
+					dirty = { type: 'ArrayPattern', elements: [dirty] };
+				}
+
+				properties.update = x`function #update(${ctx}, ${dirty}) {
 					${this.maintain_context && b`#ctx = ${ctx};`}
 					${this.chunks.update}
 				}`;

src/compiler/compile/render_dom/Renderer.ts

@@ -1,14 +1,27 @@
 import Block from './Block';
-import { CompileOptions } from '../../interfaces';
+import { CompileOptions, Var } from '../../interfaces';
 import Component from '../Component';
 import FragmentWrapper from './wrappers/Fragment';
 import { x } from 'code-red';
-import { Node, Identifier } from 'estree';
+import { Node, Identifier, MemberExpression, Literal, Expression, BinaryExpression } from 'estree';
+import flatten_reference from '../utils/flatten_reference';
+
+interface ContextMember {
+	name: string;
+	index: Literal;
+	is_contextual: boolean;
+	is_non_contextual: boolean;
+	variable: Var;
+	priority: number;
+}
 
 export default class Renderer {
 	component: Component; // TODO Maybe Renderer shouldn't know about Component?
 	options: CompileOptions;
 
+	context: ContextMember[] = [];
+	context_lookup: Map<string, ContextMember> = new Map();
+	context_overflow: boolean;
 	blocks: Array<Block | Node | Node[]> = [];
 	readonly: Set<string> = new Set();
 	meta_bindings: Array<Node | Node[]> = []; // initial values for e.g. window.innerWidth, if there's a <svelte:window> meta tag
@@ -27,6 +40,24 @@ export default class Renderer {
 
 		this.file_var = options.dev && this.component.get_unique_name('file');
 
+		component.vars.filter(v => !v.hoistable || (v.export_name && !v.module)).forEach(v => this.add_to_context(v.name));
+
+		// ensure store values are included in context
+		component.vars.filter(v => v.subscribable).forEach(v => this.add_to_context(`$${v.name}`));
+
+		if (component.var_lookup.has('$$props')) {
+			this.add_to_context('$$props');
+		}
+
+		if (component.slots.size > 0) {
+			this.add_to_context('$$scope');
+			this.add_to_context('$$slots');
+		}
+
+		if (this.binding_groups.length > 0) {
+			this.add_to_context('$$binding_groups');
+		}
+
 		// main block
 		this.block = new Block({
 			renderer: this,
@@ -50,6 +81,8 @@ export default class Renderer {
 			null
 		);
 
+		this.context_overflow = this.context.length > 31;
+
 		// TODO messy
 		this.blocks.forEach(block => {
 			if (block instanceof Block) {
@@ -60,5 +93,195 @@ export default class Renderer {
 		this.block.assign_variable_names();
 
 		this.fragment.render(this.block, null, x`#nodes` as Identifier);
+
+		this.context.forEach(member => {
+			const { variable } = member;
+			if (variable) {
+				member.priority += 2;
+				if (variable.mutated || variable.reassigned) member.priority += 4;
+
+				// these determine whether variable is included in initial context
+				// array, so must have the highest priority
+				if (variable.export_name) member.priority += 8;
+				if (variable.referenced) member.priority += 16;
+			}
+
+			if (!member.is_contextual) {
+				member.priority += 1;
+			}
+		});
+
+		this.context.sort((a, b) => (b.priority - a.priority) || ((a.index.value as number) - (b.index.value as number)));
+		this.context.forEach((member, i) => member.index.value = i);
+	}
+
+	add_to_context(name: string, contextual = false) {
+		if (!this.context_lookup.has(name)) {
+			const member: ContextMember = {
+				name,
+				index: { type: 'Literal', value: this.context.length }, // index is updated later, but set here to preserve order within groups
+				is_contextual: false,
+				is_non_contextual: false, // shadowed vars could be contextual and non-contextual
+				variable: null,
+				priority: 0
+			};
+
+			this.context_lookup.set(name, member);
+			this.context.push(member);
+		}
+
+		const member = this.context_lookup.get(name);
+
+		if (contextual) {
+			member.is_contextual = true;
+		} else {
+			member.is_non_contextual = true;
+			const variable = this.component.var_lookup.get(name);
+			member.variable = variable;
+		}
+
+		return member;
+	}
+
+	invalidate(name: string, value?) {
+		const variable = this.component.var_lookup.get(name);
+		const member = this.context_lookup.get(name);
+
+		if (variable && (variable.subscribable && (variable.reassigned || variable.export_name))) {
+			return x`${`$$subscribe_${name}`}($$invalidate(${member.index}, ${value || name}))`;
+		}
+
+		if (name[0] === '$' && name[1] !== '$') {
+			return x`${name.slice(1)}.set(${value || name})`;
+		}
+
+		if (
+			variable &&
+			!variable.referenced &&
+			!variable.is_reactive_dependency &&
+			!variable.export_name &&
+			!name.startsWith('$$')
+		) {
+			return value || name;
+		}
+
+		if (value) {
+			return x`$$invalidate(${member.index}, ${value})`;
+		}
+
+		// if this is a reactive declaration, invalidate dependencies recursively
+		const deps = new Set([name]);
+
+		deps.forEach(name => {
+			const reactive_declarations = this.component.reactive_declarations.filter(x =>
+				x.assignees.has(name)
+			);
+			reactive_declarations.forEach(declaration => {
+				declaration.dependencies.forEach(name => {
+					deps.add(name);
+				});
+			});
+		});
+
+		// TODO ideally globals etc wouldn't be here in the first place
+		const filtered = Array.from(deps).filter(n => this.context_lookup.has(n));
+		if (!filtered.length) return null;
+
+		return filtered
+			.map(n => x`$$invalidate(${this.context_lookup.get(n).index}, ${n})`)
+			.reduce((lhs, rhs) => x`${lhs}, ${rhs}}`);
+	}
+
+	dirty(names, is_reactive_declaration = false): Expression {
+		const renderer = this;
+
+		const dirty = (is_reactive_declaration
+			? x`$$self.$$.dirty`
+			: x`#dirty`) as Identifier | MemberExpression;
+
+		const get_bitmask = () => names.reduce((bitmask, name) => {
+			const member = renderer.context_lookup.get(name);
+
+			if (!member) return bitmask;
+
+			if (member.index.value === -1) {
+				throw new Error(`unset index`);
+			}
+
+			const value = member.index.value as number;
+			const i = (value / 31) | 0;
+			const n = 1 << (value % 31);
+
+			if (!bitmask[i]) bitmask[i] = { n: 0, names: [] };
+
+			bitmask[i].n |= n;
+			bitmask[i].names.push(name);
+
+			return bitmask;
+		}, Array((this.context.length / 31) | 0).fill(null));
+
+		let operator;
+		let left;
+		let right;
+
+		return {
+			get type() {
+				// we make the type a getter, even though it's always
+				// a BinaryExpression, because it gives us an opportunity
+				// to lazily create the node. TODO would be better if
+				// context was determined before rendering, so that
+				// this indirection was unnecessary
+
+				const bitmask = get_bitmask();
+
+				if (renderer.context_overflow) {
+					const expression = bitmask
+						.map((b, i) => ({ b, i }))
+						.filter(({ b }) => b)
+						.map(({ b, i }) => x`${dirty}[${i}] & /*${b.names.join(', ')}*/ ${b.n}`)
+						.reduce((lhs, rhs) => x`${lhs} | ${rhs}`);
+
+					({ operator, left, right } = expression);
+				} else {
+					({ operator, left, right } = x`${dirty} & /*${names.join(', ')}*/ ${bitmask[0] ? bitmask[0].n : 0}` as BinaryExpression); // TODO the `: 0` case should never apply
+				}
+
+				return 'BinaryExpression';
+			},
+			get operator() {
+				return operator;
+			},
+			get left() {
+				return left;
+			},
+			get right() {
+				return right;
+			}
+		} as Expression;
+	}
+
+	reference(node: string | Identifier | MemberExpression) {
+		if (typeof node === 'string') {
+			node = { type: 'Identifier', name: node };
+		}
+
+		const { name, nodes } = flatten_reference(node);
+		const member = this.context_lookup.get(name);
+
+		// TODO is this correct?
+		if (this.component.var_lookup.get(name)) {
+			this.component.add_reference(name);
+		}
+
+		if (member !== undefined) {
+			const replacement = x`/*${member.name}*/ #ctx[${member.index}]` as MemberExpression;
+
+			if (nodes[0].loc) replacement.object.loc = nodes[0].loc;
+			nodes[0] = replacement;
+
+			return nodes.reduce((lhs, rhs) => x`${lhs}.${rhs}`);
+		}
+
+		return node;
 	}
 }

src/compiler/compile/render_dom/index.ts

@@ -3,11 +3,10 @@ import Component from '../Component';
 import Renderer from './Renderer';
 import { CompileOptions } from '../../interfaces';
 import { walk } from 'estree-walker';
-import add_to_set from '../utils/add_to_set';
 import { extract_names } from '../utils/scope';
-import { invalidate } from '../utils/invalidate';
+import { invalidate } from './invalidate';
 import Block from './Block';
-import { ClassDeclaration, FunctionExpression, Node, Statement, ObjectExpression } from 'estree';
+import { ClassDeclaration, FunctionExpression, Node, Statement, ObjectExpression, Expression } from 'estree';
 
 export default function dom(
 	component: Component,
@@ -80,12 +79,12 @@ export default function dom(
 	const set = (uses_props || writable_props.length > 0 || component.slots.size > 0)
 		? x`
 			${$$props} => {
-				${uses_props && component.invalidate('$$props', x`$$props = @assign(@assign({}, $$props), $$new_props)`)}
+				${uses_props && renderer.invalidate('$$props', x`$$props = @assign(@assign({}, $$props), @exclude_internal_props($$new_props))`)}
 				${writable_props.map(prop =>
-					b`if ('${prop.export_name}' in ${$$props}) ${component.invalidate(prop.name, x`${prop.name} = ${$$props}.${prop.export_name}`)};`
+					b`if ('${prop.export_name}' in ${$$props}) ${renderer.invalidate(prop.name, x`${prop.name} = ${$$props}.${prop.export_name}`)};`
 				)}
 				${component.slots.size > 0 &&
-				b`if ('$$scope' in ${$$props}) ${component.invalidate('$$scope', x`$$scope = ${$$props}.$$scope`)};`}
+				b`if ('$$scope' in ${$$props}) ${renderer.invalidate('$$scope', x`$$scope = ${$$props}.$$scope`)};`}
 			}
 		`
 		: null;
@@ -105,7 +104,7 @@ export default function dom(
 				kind: 'get',
 				key: { type: 'Identifier', name: prop.export_name },
 				value: x`function() {
-					return ${prop.hoistable ? prop.name : x`this.$$.ctx.${prop.name}`}
+					return ${prop.hoistable ? prop.name : x`this.$$.ctx[${renderer.context_lookup.get(prop.name).index}]`}
 				}`
 			});
 		} else if (component.compile_options.dev) {
@@ -161,7 +160,7 @@ export default function dom(
 				const { ctx: #ctx } = this.$$;
 				const props = ${options.customElement ? x`this.attributes` : x`options.props || {}`};
 				${expected.map(prop => b`
-				if (#ctx.${prop.name} === undefined && !('${prop.export_name}' in props)) {
+				if (${renderer.reference(prop.name)} === undefined && !('${prop.export_name}' in props)) {
 					@_console.warn("<${component.tag}> was created without expected prop '${prop.export_name}'");
 				}`)}
 			`;
@@ -180,9 +179,9 @@ export default function dom(
 		const writable_vars = component.vars.filter(variable => !variable.module && variable.writable);
 		inject_state = (uses_props || writable_vars.length > 0) ? x`
 			${$$props} => {
-				${uses_props && component.invalidate('$$props', x`$$props = @assign(@assign({}, $$props), $$new_props)`)}
+				${uses_props && renderer.invalidate('$$props', x`$$props = @assign(@assign({}, $$props), $$new_props)`)}
 				${writable_vars.map(prop => b`
-					if ('${prop.name}' in $$props) ${component.invalidate(prop.name, x`${prop.name} = ${$$props}.${prop.name}`)};
+					if ('${prop.name}' in $$props) ${renderer.invalidate(prop.name, x`${prop.name} = ${$$props}.${prop.name}`)};
 				`)}
 			}
 		` : x`
@@ -216,17 +215,18 @@ export default function dom(
 					// onto the initial function call
 					const names = new Set(extract_names(assignee));
 
-					this.replace(invalidate(component, scope, node, names));
+					this.replace(invalidate(renderer, scope, node, names));
 				}
 			}
 		});
 
 		component.rewrite_props(({ name, reassigned, export_name }) => {
 			const value = `$${name}`;
+			const i = renderer.context_lookup.get(`$${name}`).index;
 
 			const insert = (reassigned || export_name)
 				? b`${`$$subscribe_${name}`}()`
-				: b`@component_subscribe($$self, ${name}, #value => $$invalidate('${value}', ${value} = #value))`;
+				: b`@component_subscribe($$self, ${name}, #value => $$invalidate(${i}, ${value} = #value))`;
 
 			if (component.compile_options.dev) {
 				return b`@validate_store(${name}, '${name}'); ${insert}`;
@@ -256,12 +256,6 @@ export default function dom(
 		${component.fully_hoisted}
 	`);
 
-	const filtered_declarations = component.vars
-		.filter(v => ((v.referenced || v.export_name) && !v.hoistable))
-		.map(v => p`${v.name}`);
-
-	if (uses_props) filtered_declarations.push(p`$$props: $$props = @exclude_internal_props($$props)`);
-
 	const filtered_props = props.filter(prop => {
 		const variable = component.var_lookup.get(prop.name);
 
@@ -272,22 +266,25 @@ export default function dom(
 
 	const reactive_stores = component.vars.filter(variable => variable.name[0] === '$' && variable.name[1] !== '$');
 
-	if (component.slots.size > 0) {
-		filtered_declarations.push(p`$$slots`, p`$$scope`);
-	}
+	const instance_javascript = component.extract_javascript(component.ast.instance);
 
-	if (renderer.binding_groups.length > 0) {
-		filtered_declarations.push(p`$$binding_groups`);
+	let i = renderer.context.length;
+	while (i--) {
+		const member = renderer.context[i];
+		if (member.variable) {
+			if (member.variable.referenced || member.variable.export_name) break;
+		} else if (member.is_non_contextual) {
+			break;
+		}
 	}
-
-	const instance_javascript = component.extract_javascript(component.ast.instance);
+	const initial_context = renderer.context.slice(0, i + 1);
 
 	const has_definition = (
 		(instance_javascript && instance_javascript.length > 0) ||
 		filtered_props.length > 0 ||
 		uses_props ||
 		component.partly_hoisted.length > 0 ||
-		filtered_declarations.length > 0 ||
+		initial_context.length > 0 ||
 		component.reactive_declarations.length > 0
 	);
 
@@ -295,11 +292,6 @@ export default function dom(
 		? component.alias('instance')
 		: { type: 'Literal', value: null };
 
-	const all_reactive_dependencies = new Set();
-	component.reactive_declarations.forEach(d => {
-		add_to_set(all_reactive_dependencies, d.dependencies);
-	});
-
 	const reactive_store_subscriptions = reactive_stores
 		.filter(store => {
 			const variable = component.var_lookup.get(store.name.slice(1));
@@ -307,7 +299,7 @@ export default function dom(
 		})
 		.map(({ name }) => b`
 			${component.compile_options.dev && b`@validate_store(${name.slice(1)}, '${name.slice(1)}');`}
-			@component_subscribe($$self, ${name.slice(1)}, $$value => $$invalidate('${name}', ${name} = $$value));
+			@component_subscribe($$self, ${name.slice(1)}, $$value => $$invalidate(${renderer.context_lookup.get(name).index}, ${name} = $$value));
 		`);
 
 	const resubscribable_reactive_store_unsubscribers = reactive_stores
@@ -327,12 +319,10 @@ export default function dom(
 
 			const writable = dependencies.filter(n => {
 				const variable = component.var_lookup.get(n);
-				return variable && (variable.writable || variable.mutated);
+				return variable && (variable.export_name || variable.mutated || variable.reassigned);
 			});
 
-			const condition = !uses_props && writable.length > 0 && (writable
-				.map(n => x`#changed.${n}`)
-				.reduce((lhs, rhs) => x`${lhs} || ${rhs}`));
+			const condition = !uses_props && writable.length > 0 && renderer.dirty(writable, true);
 
 			let statement = d.node; // TODO remove label (use d.node.body) if it's not referenced
 
@@ -358,7 +348,9 @@ export default function dom(
 			if (store && (store.reassigned || store.export_name)) {
 				const unsubscribe = `$$unsubscribe_${name}`;
 				const subscribe = `$$subscribe_${name}`;
-				return b`let ${$name}, ${unsubscribe} = @noop, ${subscribe} = () => (${unsubscribe}(), ${unsubscribe} = @subscribe(${name}, $$value => $$invalidate('${$name}', ${$name} = $$value)), ${name})`;
+				const i = renderer.context_lookup.get($name).index;
+
+				return b`let ${$name}, ${unsubscribe} = @noop, ${subscribe} = () => (${unsubscribe}(), ${unsubscribe} = @subscribe(${name}, $$value => $$invalidate(${i}, ${$name} = $$value)), ${name})`;
 			}
 
 			return b`let ${$name};`;
@@ -375,20 +367,11 @@ export default function dom(
 		}
 
 		const return_value = {
-			type: 'ObjectExpression',
-			properties: filtered_declarations
-		};
-
-		const reactive_dependencies = {
-			type: 'ObjectPattern',
-			properties: Array.from(all_reactive_dependencies).map(name => {
-				return {
-					type: 'Property',
-					kind: 'init',
-					key: { type: 'Identifier', name },
-					value: { type: 'Literal', value: 1 }
-				};
-			})
+			type: 'ArrayExpression',
+			elements: initial_context.map(member => ({
+				type: 'Identifier',
+				name: member.name
+			}) as Expression)
 		};
 
 		body.push(b`
@@ -418,22 +401,32 @@ export default function dom(
 				${injected.map(name => b`let ${name};`)}
 
 				${reactive_declarations.length > 0 && b`
-				$$self.$$.update = (#changed = ${reactive_dependencies}) => {
+				$$self.$$.update = () => {
 					${reactive_declarations}
 				};
 				`}
 
 				${fixed_reactive_declarations}
 
+				${uses_props && b`$$props = @exclude_internal_props($$props);`}
+
 				return ${return_value};
 			}
 		`);
 	}
 
-	const prop_names = x`{
-		${props.map(v => p`${v.export_name}: ${v.export_name === v.name ? 0 : x`"${v.name}"`}}`)}
+	const prop_indexes = x`{
+		${props.filter(v => v.export_name && !v.module).map(v => p`${v.export_name}: ${renderer.context_lookup.get(v.name).index}`)}
 	}` as ObjectExpression;
 
+	let dirty;
+	if (renderer.context_overflow) {
+		dirty = x`[]`;
+		for (let i = 0; i < renderer.context.length; i += 31) {
+			dirty.elements.push(x`-1`);
+		}
+	}
+
 	if (options.customElement) {
 		const declaration = b`
 			class ${name} extends @SvelteElement {
@@ -442,7 +435,7 @@ export default function dom(
 
 					${css.code && b`this.shadowRoot.innerHTML = \`<style>${css.code.replace(/\\/g, '\\\\')}${options.dev ? `\n/*# sourceMappingURL=${css.map.toUrl()} */` : ''}</style>\`;`}
 
-					@init(this, { target: this.shadowRoot }, ${definition}, ${has_create_fragment ? 'create_fragment': 'null'}, ${not_equal}, ${prop_names});
+					@init(this, { target: this.shadowRoot }, ${definition}, ${has_create_fragment ? 'create_fragment': 'null'}, ${not_equal}, ${prop_indexes}, ${dirty});
 
 					${dev_props_check}
 
@@ -494,7 +487,7 @@ export default function dom(
 				constructor(options) {
 					super(${options.dev && `options`});
 					${should_add_css && b`if (!@_document.getElementById("${component.stylesheet.id}-style")) ${add_css}();`}
-					@init(this, options, ${definition}, ${has_create_fragment ? 'create_fragment': 'null'}, ${not_equal}, ${prop_names});
+					@init(this, options, ${definition}, ${has_create_fragment ? 'create_fragment': 'null'}, ${not_equal}, ${prop_indexes}, ${dirty});
 					${options.dev && b`@dispatch_dev("SvelteRegisterComponent", { component: this, tagName: "${name.name}", options, id: create_fragment.name });`}
 
 					${dev_props_check}

src/compiler/compile/render_dom/invalidate.ts

@@ -1,10 +1,12 @@
-import Component from '../Component';
 import { nodes_match } from '../../utils/nodes_match';
-import { Scope } from './scope';
+import { Scope } from '../utils/scope';
 import { x } from 'code-red';
 import { Node } from 'estree';
+import Renderer from './Renderer';
+
+export function invalidate(renderer: Renderer, scope: Scope, node: Node, names: Set<string>) {
+	const { component } = renderer;
 
-export function invalidate(component: Component, scope: Scope, node: Node, names: Set<string>) {
 	const [head, ...tail] = Array.from(names).filter(name => {
 		const owner = scope.find_owner(name);
 		if (owner && owner !== component.instance_scope) return false;
@@ -17,6 +19,7 @@ export function invalidate(component: Component, scope: Scope, node: Node, names
 			!variable.module &&
 			(
 				variable.referenced ||
+				variable.subscribable ||
 				variable.is_reactive_dependency ||
 				variable.export_name ||
 				variable.name[0] === '$'
@@ -28,12 +31,12 @@ export function invalidate(component: Component, scope: Scope, node: Node, names
 		component.has_reactive_assignments = true;
 
 		if (node.type === 'AssignmentExpression' && node.operator === '=' && nodes_match(node.left, node.right) && tail.length === 0) {
-			return component.invalidate(head);
+			return renderer.invalidate(head);
 		} else {
 			const is_store_value = head[0] === '$';
 			const variable = component.var_lookup.get(head);
 
-			const extra_args = tail.map(name => component.invalidate(name));
+			const extra_args = tail.map(name => renderer.invalidate(name));
 
 			const pass_value = (
 				extra_args.length > 0 ||
@@ -48,8 +51,9 @@ export function invalidate(component: Component, scope: Scope, node: Node, names
 				});
 			}
 
-			const callee = is_store_value ? `@set_store_value` : `$$invalidate`;
-			let invalidate = x`${callee}(${is_store_value ? head.slice(1) : x`"${head}"`}, ${node}, ${extra_args})`;
+			let invalidate = is_store_value
+				? x`@set_store_value(${head.slice(1)}, ${node}, ${extra_args})`
+				: x`$$invalidate(${renderer.context_lookup.get(head).index}, ${node}, ${extra_args})`;
 
 			if (variable.subscribable && variable.reassigned) {
 				const subscribe = `$$subscribe_${head}`;

src/compiler/compile/render_dom/wrappers/AwaitBlock.ts

@@ -8,7 +8,6 @@ import FragmentWrapper from './Fragment';
 import PendingBlock from '../../nodes/PendingBlock';
 import ThenBlock from '../../nodes/ThenBlock';
 import CatchBlock from '../../nodes/CatchBlock';
-import { changed } from './shared/changed';
 import { Identifier } from 'estree';
 
 class AwaitBlockBranch extends Wrapper {
@@ -119,6 +118,9 @@ export default class AwaitBlockWrapper extends Wrapper {
 		if (has_outros) {
 			block.add_outro();
 		}
+
+		if (this.node.value) block.renderer.add_to_context(this.node.value, true);
+		if (this.node.error) block.renderer.add_to_context(this.node.error, true);
 	}
 
 	render(
@@ -138,6 +140,9 @@ export default class AwaitBlockWrapper extends Wrapper {
 
 		block.maintain_context = true;
 
+		const value_index = this.node.value && block.renderer.context_lookup.get(this.node.value).index;
+		const error_index = this.node.error && block.renderer.context_lookup.get(this.node.error).index;
+
 		const info_props: any = x`{
 			ctx: #ctx,
 			current: null,
@@ -145,8 +150,8 @@ export default class AwaitBlockWrapper extends Wrapper {
 			pending: ${this.pending.block.name},
 			then: ${this.then.block.name},
 			catch: ${this.catch.block.name},
-			value: ${this.then.block.name && x`"${this.node.value}"`},
-			error: ${this.catch.block.name && x`"${this.node.error}"`},
+			value: ${value_index},
+			error: ${error_index},
 			blocks: ${this.pending.block.has_outro_method && x`[,,,]`}
 		}`;
 
@@ -187,7 +192,7 @@ export default class AwaitBlockWrapper extends Wrapper {
 
 		if (dependencies.length > 0) {
 			const condition = x`
-				${changed(dependencies)} &&
+				${block.renderer.dirty(dependencies)} &&
 				${promise} !== (${promise} = ${snippet}) &&
 				@handle_promise(${promise}, ${info})`;
 
@@ -198,9 +203,11 @@ export default class AwaitBlockWrapper extends Wrapper {
 			if (this.pending.block.has_update_method) {
 				block.chunks.update.push(b`
 					if (${condition}) {
-						// nothing
+
 					} else {
-						${info}.block.p(#changed, @assign(@assign({}, #ctx), ${info}.resolved));
+						const #child_ctx = #ctx.slice();
+						#child_ctx[${value_index}] = ${info}.resolved;
+						${info}.block.p(#child_ctx, #dirty);
 					}
 				`);
 			} else {
@@ -211,7 +218,11 @@ export default class AwaitBlockWrapper extends Wrapper {
 		} else {
 			if (this.pending.block.has_update_method) {
 				block.chunks.update.push(b`
-					${info}.block.p(#changed, @assign(@assign({}, #ctx), ${info}.resolved));
+					{
+						const #child_ctx = #ctx.slice();
+						#child_ctx[${value_index}] = ${info}.resolved;
+						${info}.block.p(#child_ctx, #dirty);
+					}
 				`);
 			}
 		}

src/compiler/compile/render_dom/wrappers/DebugTag.ts

@@ -5,7 +5,6 @@ import DebugTag from '../../nodes/DebugTag';
 import add_to_set from '../../utils/add_to_set';
 import { b, p } from 'code-red';
 import { Identifier, DebuggerStatement } from 'estree';
-import { changed } from './shared/changed';
 
 export default class DebugTagWrapper extends Wrapper {
 	node: DebugTag;
@@ -60,17 +59,17 @@ export default class DebugTagWrapper extends Wrapper {
 					const variable = var_lookup.get(e.node.name);
 					return !(variable && variable.hoistable);
 				})
-				.map(e => p`${e.node.name}`);
+				.map(e => e.node.name);
 
 			const logged_identifiers = this.node.expressions.map(e => p`${e.node.name}`);
 
 			const debug_statements = b`
-				const { ${contextual_identifiers} } = #ctx;
+				${contextual_identifiers.map(name => b`const ${name} = ${renderer.reference(name)};`)}
 				@_console.${log}({ ${logged_identifiers} });
 				debugger;`;
 
 			if (dependencies.size) {
-				const condition = changed(Array.from(dependencies));
+				const condition = renderer.dirty(Array.from(dependencies));
 
 				block.chunks.update.push(b`
 					if (${condition}) {

src/compiler/compile/render_dom/wrappers/EachBlock.ts

@@ -7,7 +7,6 @@ import FragmentWrapper from './Fragment';
 import { b, x } from 'code-red';
 import ElseBlock from '../../nodes/ElseBlock';
 import { Identifier, Node } from 'estree';
-import { changed } from './shared/changed';
 
 export class ElseBlockWrapper extends Wrapper {
 	node: ElseBlock;
@@ -81,6 +80,10 @@ export default class EachBlockWrapper extends Wrapper {
 		const { dependencies } = node.expression;
 		block.add_dependencies(dependencies);
 
+		this.node.contexts.forEach(context => {
+			renderer.add_to_context(context.key.name, true);
+		});
+
 		this.block = block.child({
 			comment: create_debugging_comment(this.node, this.renderer.component),
 			name: renderer.component.get_unique_name('create_each_block'),
@@ -119,6 +122,9 @@ export default class EachBlockWrapper extends Wrapper {
 		const each_block_value = renderer.component.get_unique_name(`${this.var.name}_value`);
 		const iterations = block.get_unique_name(`${this.var.name}_blocks`);
 
+		renderer.add_to_context(each_block_value.name, true);
+		renderer.add_to_context(this.index_name.name, true);
+
 		this.vars = {
 			create_each_block: this.block.name,
 			each_block_value,
@@ -190,18 +196,19 @@ export default class EachBlockWrapper extends Wrapper {
 			? !this.next.is_dom_node() :
 			!parent_node || !this.parent.is_dom_node();
 
-		this.context_props = this.node.contexts.map(prop => b`child_ctx.${prop.key.name} = ${prop.modifier(x`list[i]`)};`);
+		this.context_props = this.node.contexts.map(prop => b`child_ctx[${renderer.context_lookup.get(prop.key.name).index}] = ${prop.modifier(x`list[i]`)};`);
 
-		if (this.node.has_binding) this.context_props.push(b`child_ctx.${this.vars.each_block_value} = list;`);
-		if (this.node.has_binding || this.node.index) this.context_props.push(b`child_ctx.${this.index_name} = i;`);
+		if (this.node.has_binding) this.context_props.push(b`child_ctx[${renderer.context_lookup.get(this.vars.each_block_value.name).index}] = list;`);
+		if (this.node.has_binding || this.node.index) this.context_props.push(b`child_ctx[${renderer.context_lookup.get(this.index_name.name).index}] = i;`);
 
 		const snippet = this.node.expression.manipulate(block);
 
 		block.chunks.init.push(b`let ${this.vars.each_block_value} = ${snippet};`);
 
+		// TODO which is better — Object.create(array) or array.slice()?
 		renderer.blocks.push(b`
 			function ${this.vars.get_each_context}(#ctx, list, i) {
-				const child_ctx = @_Object.create(#ctx);
+				const child_ctx = #ctx.slice();
 				${this.context_props}
 				return child_ctx;
 			}
@@ -270,7 +277,7 @@ export default class EachBlockWrapper extends Wrapper {
 			if (this.else.block.has_update_method) {
 				block.chunks.update.push(b`
 					if (!${this.vars.data_length} && ${each_block_else}) {
-						${each_block_else}.p(#changed, #ctx);
+						${each_block_else}.p(#ctx, #dirty);
 					} else if (!${this.vars.data_length}) {
 						${each_block_else} = ${this.else.block.name}(#ctx);
 						${each_block_else}.c();
@@ -396,7 +403,7 @@ export default class EachBlockWrapper extends Wrapper {
 
 			${this.block.has_outros && b`@group_outros();`}
 			${this.node.has_animation && b`for (let #i = 0; #i < ${view_length}; #i += 1) ${iterations}[#i].r();`}
-			${iterations} = @update_keyed_each(${iterations}, #changed, ${get_key}, ${dynamic ? 1 : 0}, #ctx, ${this.vars.each_block_value}, ${lookup}, ${update_mount_node}, ${destroy}, ${create_each_block}, ${update_anchor_node}, ${this.vars.get_each_context});
+			${iterations} = @update_keyed_each(${iterations}, #dirty, ${get_key}, ${dynamic ? 1 : 0}, #ctx, ${this.vars.each_block_value}, ${lookup}, ${update_mount_node}, ${destroy}, ${create_each_block}, ${update_anchor_node}, ${this.vars.get_each_context});
 			${this.node.has_animation && b`for (let #i = 0; #i < ${view_length}; #i += 1) ${iterations}[#i].a();`}
 			${this.block.has_outros && b`@check_outros();`}
 		`);
@@ -469,9 +476,8 @@ export default class EachBlockWrapper extends Wrapper {
 			}
 		`);
 
-		const all_dependencies = new Set(this.block.dependencies);
-		const { dependencies } = this.node.expression;
-		dependencies.forEach((dependency: string) => {
+		const all_dependencies = new Set(this.block.dependencies); // TODO should be dynamic deps only
+		this.node.expression.dynamic_dependencies().forEach((dependency: string) => {
 			all_dependencies.add(dependency);
 		});
 
@@ -481,7 +487,7 @@ export default class EachBlockWrapper extends Wrapper {
 			const for_loop_body = this.block.has_update_method
 				? b`
 					if (${iterations}[#i]) {
-						${iterations}[#i].p(#changed, child_ctx);
+						${iterations}[#i].p(child_ctx, #dirty);
 						${has_transitions && b`@transition_in(${this.vars.iterations}[#i], 1);`}
 					} else {
 						${iterations}[#i] = ${create_each_block}(child_ctx);
@@ -554,7 +560,7 @@ export default class EachBlockWrapper extends Wrapper {
 			`;
 
 			block.chunks.update.push(b`
-				if (${changed(Array.from(all_dependencies))}) {
+				if (${block.renderer.dirty(Array.from(all_dependencies))}) {
 					${update}
 				}
 			`);

src/compiler/compile/render_dom/wrappers/Element/Attribute.ts

@@ -6,7 +6,6 @@ import { string_literal } from '../../../utils/stringify';
 import { b, x } from 'code-red';
 import Expression from '../../../nodes/shared/Expression';
 import Text from '../../../nodes/Text';
-import { changed } from '../shared/changed';
 
 export default class AttributeWrapper {
 	node: Attribute;
@@ -140,7 +139,7 @@ export default class AttributeWrapper {
 		}
 
 		if (dependencies.length > 0) {
-			let condition = changed(dependencies);
+			let condition = block.renderer.dirty(dependencies);
 
 			if (should_cache) {
 				condition = is_src
@@ -197,8 +196,8 @@ export default class AttributeWrapper {
 		}
 
 		let value = this.node.name === 'class'
-			? this.get_class_name_text()
-			: this.render_chunks().reduce((lhs, rhs) => x`${lhs} + ${rhs}`);
+			? this.get_class_name_text(block)
+			: this.render_chunks(block).reduce((lhs, rhs) => x`${lhs} + ${rhs}`);
 
 		// '{foo} {bar}' — treat as string concatenation
 		if (this.node.chunks[0].type !== 'Text') {
@@ -208,9 +207,9 @@ export default class AttributeWrapper {
 		return value;
 	}
 
-	get_class_name_text() {
+	get_class_name_text(block) {
 		const scoped_css = this.node.chunks.some((chunk: Text) => chunk.synthetic);
-		const rendered = this.render_chunks();
+		const rendered = this.render_chunks(block);
 
 		if (scoped_css && rendered.length === 2) {
 			// we have a situation like class={possiblyUndefined}
@@ -220,13 +219,13 @@ export default class AttributeWrapper {
 		return rendered.reduce((lhs, rhs) => x`${lhs} + ${rhs}`);
 	}
 
-	render_chunks() {
+	render_chunks(block: Block) {
 		return this.node.chunks.map((chunk) => {
 			if (chunk.type === 'Text') {
 				return string_literal(chunk.data);
 			}
 
-			return chunk.manipulate();
+			return chunk.manipulate(block);
 		});
 	}
 

src/compiler/compile/render_dom/wrappers/Element/Binding.ts

@@ -6,7 +6,6 @@ import Block from '../../Block';
 import Renderer from '../../Renderer';
 import flatten_reference from '../../../utils/flatten_reference';
 import EachBlock from '../../../nodes/EachBlock';
-import { changed } from '../shared/changed';
 import { Node, Identifier } from 'estree';
 
 export default class BindingWrapper {
@@ -91,7 +90,7 @@ export default class BindingWrapper {
 		const dependency_array = [...this.node.expression.dependencies];
 
 		if (dependency_array.length > 0) {
-			update_conditions.push(changed(dependency_array));
+			update_conditions.push(block.renderer.dirty(dependency_array));
 		}
 
 		if (parent.node.name === 'input') {
@@ -112,12 +111,15 @@ export default class BindingWrapper {
 			{
 				const binding_group = get_binding_group(parent.renderer, this.node.expression.node);
 
+				block.renderer.add_to_context(`$$binding_groups`);
+				const reference = block.renderer.reference(`$$binding_groups`);
+
 				block.chunks.hydrate.push(
-					b`#ctx.$$binding_groups[${binding_group}].push(${parent.var});`
+					b`${reference}[${binding_group}].push(${parent.var});`
 				);
 
 				block.chunks.destroy.push(
-					b`#ctx.$$binding_groups[${binding_group}].splice(#ctx.$$binding_groups[${binding_group}].indexOf(${parent.var}), 1);`
+					b`${reference}[${binding_group}].splice(${reference}[${binding_group}].indexOf(${parent.var}), 1);`
 				);
 				break;
 			}

src/compiler/compile/render_dom/wrappers/Element/EventHandler.ts

@@ -15,40 +15,36 @@ export default class EventHandlerWrapper {
 		this.parent = parent;
 
 		if (!node.expression) {
-			this.parent.renderer.component.add_var({
-				name: node.handler_name.name,
-				internal: true,
-				referenced: true,
-			});
+			this.parent.renderer.add_to_context(node.handler_name.name);
 
 			this.parent.renderer.component.partly_hoisted.push(b`
-        function ${node.handler_name.name}(event) {
-          @bubble($$self, event);
-        }
-      `);
+				function ${node.handler_name.name}(event) {
+					@bubble($$self, event);
+				}
+			`);
 		}
 	}
 
-  get_snippet(block) {
-		const snippet = this.node.expression ? this.node.expression.manipulate(block) : x`#ctx.${this.node.handler_name}`;
+	get_snippet(block) {
+		const snippet = this.node.expression ? this.node.expression.manipulate(block) : block.renderer.reference(this.node.handler_name);
 
 		if (this.node.reassigned) {
 			block.maintain_context = true;
 			return x`function () { ${snippet}.apply(this, arguments); }`;
 		}
 		return snippet;
-  }
+	}
 
 	render(block: Block, target: string) {
 		let snippet = this.get_snippet(block);
 
-    if (this.node.modifiers.has('preventDefault')) snippet = x`@prevent_default(${snippet})`;
+		if (this.node.modifiers.has('preventDefault')) snippet = x`@prevent_default(${snippet})`;
 		if (this.node.modifiers.has('stopPropagation')) snippet = x`@stop_propagation(${snippet})`;
 		if (this.node.modifiers.has('self')) snippet = x`@self(${snippet})`;
 
-    const args = [];
+		const args = [];
 
-    const opts = ['passive', 'once', 'capture'].filter(mod => this.node.modifiers.has(mod));
+		const opts = ['passive', 'once', 'capture'].filter(mod => this.node.modifiers.has(mod));
 		if (opts.length) {
 			args.push((opts.length === 1 && opts[0] === 'capture')
 				? TRUE
@@ -62,7 +58,7 @@ export default class EventHandlerWrapper {
 			args.push(this.node.modifiers.has('preventDefault') ? TRUE : FALSE);
 		}
 
-    block.event_listeners.push(
+		block.event_listeners.push(
 			x`@listen(${target}, "${this.node.name}", ${snippet}, ${args})`
 		);
 	}

src/compiler/compile/render_dom/wrappers/Element/StyleAttribute.ts

@@ -7,7 +7,6 @@ import { string_literal } from '../../../utils/stringify';
 import add_to_set from '../../../utils/add_to_set';
 import Expression from '../../../nodes/shared/Expression';
 import Text from '../../../nodes/Text';
-import { changed } from '../shared/changed';
 
 export interface StyleProp {
 	key: string;
@@ -46,7 +45,7 @@ export default class StyleAttributeWrapper extends AttributeWrapper {
 				// }
 
 				if (prop_dependencies.size) {
-					let condition = changed(Array.from(prop_dependencies));
+					let condition = block.renderer.dirty(Array.from(prop_dependencies));
 
 					if (block.has_outros) {
 						condition = x`!#current || ${condition}`;

src/compiler/compile/render_dom/wrappers/Element/index.ts

@@ -19,12 +19,12 @@ import add_to_set from '../../../utils/add_to_set';
 import add_event_handlers from '../shared/add_event_handlers';
 import add_actions from '../shared/add_actions';
 import create_debugging_comment from '../shared/create_debugging_comment';
-import { get_context_merger } from '../shared/get_context_merger';
+import { get_slot_definition } from '../shared/get_slot_definition';
 import bind_this from '../shared/bind_this';
-import { changed } from '../shared/changed';
 import { is_head } from '../shared/is_head';
 import { Identifier } from 'estree';
 import EventHandler from './EventHandler';
+import { extract_names } from 'periscopic';
 
 const events = [
 	{
@@ -159,6 +159,14 @@ export default class ElementWrapper extends Wrapper {
 
 		this.class_dependencies = [];
 
+		if (this.node.children.length) {
+			this.node.lets.forEach(l => {
+				extract_names(l.value || l.name).forEach(name => {
+					renderer.add_to_context(name, true);
+				});
+			});
+		}
+
 		this.attributes = this.node.attributes.map(attribute => {
 			if (attribute.name === 'slot') {
 				// TODO make separate subclass for this?
@@ -185,20 +193,17 @@ export default class ElementWrapper extends Wrapper {
 							type: 'slot'
 						});
 
-						const lets = this.node.lets;
+						const { scope, lets } = this.node;
 						const seen = new Set(lets.map(l => l.name.name));
 
 						(owner as unknown as InlineComponentWrapper).node.lets.forEach(l => {
 							if (!seen.has(l.name.name)) lets.push(l);
 						});
 
-						const fn = get_context_merger(lets);
-
-						(owner as unknown as InlineComponentWrapper).slots.set(name, {
-							block: child_block,
-							scope: this.node.scope,
-							fn
-						});
+						(owner as unknown as InlineComponentWrapper).slots.set(
+							name,
+							get_slot_definition(child_block, scope, lets)
+						);
 						this.renderer.blocks.push(child_block);
 					}
 
@@ -282,7 +287,7 @@ export default class ElementWrapper extends Wrapper {
 		const children = x`@children(${this.node.name === 'template' ? x`${node}.content` : node})`;
 
 		block.add_variable(node);
-		const render_statement = this.get_render_statement();
+		const render_statement = this.get_render_statement(block);
 		block.chunks.create.push(
 			b`${node} = ${render_statement};`
 		);
@@ -398,7 +403,7 @@ export default class ElementWrapper extends Wrapper {
 		return this.is_static_content && this.fragment.nodes.every(node => node.node.type === 'Text' || node.node.type === 'MustacheTag');
 	}
 
-	get_render_statement() {
+	get_render_statement(block: Block) {
 		const { name, namespace } = this.node;
 
 		if (namespace === 'http://www.w3.org/2000/svg') {
@@ -411,7 +416,7 @@ export default class ElementWrapper extends Wrapper {
 
 		const is = this.attributes.find(attr => attr.node.name === 'is');
 		if (is) {
-			return x`@element_is("${name}", ${is.render_chunks().reduce((lhs, rhs) => x`${lhs} + ${rhs}`)});`;
+			return x`@element_is("${name}", ${is.render_chunks(block).reduce((lhs, rhs) => x`${lhs} + ${rhs}`)});`;
 		}
 
 		return x`@element("${name}")`;
@@ -455,18 +460,13 @@ export default class ElementWrapper extends Wrapper {
 
 		groups.forEach(group => {
 			const handler = renderer.component.get_unique_name(`${this.var.name}_${group.events.join('_')}_handler`);
-
-			renderer.component.add_var({
-				name: handler.name,
-				internal: true,
-				referenced: true
-			});
+			renderer.add_to_context(handler.name);
 
 			// TODO figure out how to handle locks
 			const needs_lock = group.bindings.some(binding => binding.needs_lock);
 
-			const dependencies = new Set();
-			const contextual_dependencies = new Set();
+			const dependencies: Set<string> = new Set();
+			const contextual_dependencies: Set<string> = new Set();
 
 			group.bindings.forEach(binding => {
 				// TODO this is a mess
@@ -488,10 +488,12 @@ export default class ElementWrapper extends Wrapper {
 
 			const has_local_function = contextual_dependencies.size > 0 || needs_lock || animation_frame;
 
-			let callee;
+			let callee = renderer.reference(handler);
 
 			// TODO dry this out — similar code for event handlers and component bindings
 			if (has_local_function) {
+				const args = Array.from(contextual_dependencies).map(name => renderer.reference(name));
+
 				// need to create a block-local function that calls an instance-level function
 				if (animation_frame) {
 					block.chunks.init.push(b`
@@ -501,43 +503,33 @@ export default class ElementWrapper extends Wrapper {
 								${animation_frame} = @raf(${handler});
 								${needs_lock && b`${lock} = true;`}
 							}
-							#ctx.${handler}.call(${this.var}, ${contextual_dependencies.size > 0 ? '#ctx' : null});
+							${callee}.call(${this.var}, ${args});
 						}
 					`);
 				} else {
 					block.chunks.init.push(b`
 						function ${handler}() {
 							${needs_lock && b`${lock} = true;`}
-							#ctx.${handler}.call(${this.var}, ${contextual_dependencies.size > 0 ? '#ctx' : null});
+							${callee}.call(${this.var}, ${args});
 						}
 					`);
 				}
 
 				callee = handler;
-			} else {
-				callee = x`#ctx.${handler}`;
 			}
 
-			const arg = contextual_dependencies.size > 0 && {
-				type: 'ObjectPattern',
-				properties: Array.from(contextual_dependencies).map(name => {
-					const id = { type: 'Identifier', name };
-					return {
-						type: 'Property',
-						kind: 'init',
-						key: id,
-						value: id
-					};
-				})
-			};
+			const params = Array.from(contextual_dependencies).map(name => ({
+				type: 'Identifier',
+				name
+			}));
 
 			this.renderer.component.partly_hoisted.push(b`
-				function ${handler}(${arg}) {
+				function ${handler}(${params}) {
 					${group.bindings.map(b => b.handler.mutation)}
 					${Array.from(dependencies)
 						.filter(dep => dep[0] !== '$')
 						.filter(dep => !contextual_dependencies.has(dep))
-						.map(dep => b`${this.renderer.component.invalidate(dep)};`)}
+						.map(dep => b`${this.renderer.invalidate(dep)};`)}
 				}
 			`);
 
@@ -632,7 +624,7 @@ export default class ElementWrapper extends Wrapper {
 		this.attributes
 			.forEach(attr => {
 				const condition = attr.node.dependencies.size > 0
-					? changed(Array.from(attr.node.dependencies))
+					? block.renderer.dirty(Array.from(attr.node.dependencies))
 					: null;
 
 				if (attr.node.is_spread) {
@@ -685,8 +677,6 @@ export default class ElementWrapper extends Wrapper {
 		const { intro, outro } = this.node;
 		if (!intro && !outro) return;
 
-		const { component } = this.renderer;
-
 		if (intro === outro) {
 			// bidirectional transition
 			const name = block.get_unique_name(`${this.var.name}_transition`);
@@ -696,7 +686,7 @@ export default class ElementWrapper extends Wrapper {
 
 			block.add_variable(name);
 
-			const fn = component.qualify(intro.name);
+			const fn = this.renderer.reference(intro.name);
 
 			const intro_block = b`
 				@add_render_callback(() => {
@@ -740,7 +730,7 @@ export default class ElementWrapper extends Wrapper {
 					? intro.expression.manipulate(block)
 					: x`{}`;
 
-				const fn = component.qualify(intro.name);
+				const fn = this.renderer.reference(intro.name);
 
 				let intro_block;
 
@@ -782,7 +772,7 @@ export default class ElementWrapper extends Wrapper {
 					? outro.expression.manipulate(block)
 					: x`{}`;
 
-				const fn = component.qualify(outro.name);
+				const fn = this.renderer.reference(outro.name);
 
 				if (!intro) {
 					block.chunks.intro.push(b`
@@ -814,7 +804,6 @@ export default class ElementWrapper extends Wrapper {
 	add_animation(block: Block) {
 		if (!this.node.animation) return;
 
-		const { component } = this.renderer;
 		const { outro } = this.node;
 
 		const rect = block.get_unique_name('rect');
@@ -835,7 +824,7 @@ export default class ElementWrapper extends Wrapper {
 
 		const params = this.node.animation.expression ? this.node.animation.expression.manipulate(block) : x`{}`;
 
-		const name = component.qualify(this.node.animation.name);
+		const name = this.renderer.reference(this.node.animation.name);
 
 		block.chunks.animate.push(b`
 			${stop_animation}();
@@ -844,7 +833,7 @@ export default class ElementWrapper extends Wrapper {
 	}
 
 	add_actions(block: Block) {
-		add_actions(this.renderer.component, block, this.var, this.node.actions);
+		add_actions(block, this.var, this.node.actions);
 	}
 
 	add_classes(block: Block) {
@@ -868,7 +857,7 @@ export default class ElementWrapper extends Wrapper {
 				block.chunks.update.push(updater);
 			} else if ((dependencies && dependencies.size > 0) || this.class_dependencies.length) {
 				const all_dependencies = this.class_dependencies.concat(...dependencies);
-				const condition = changed(all_dependencies);
+				const condition = block.renderer.dirty(all_dependencies);
 
 				block.chunks.update.push(b`
 					if (${condition}) {

src/compiler/compile/render_dom/wrappers/IfBlock.ts

@@ -10,7 +10,6 @@ import { b, x } from 'code-red';
 import { walk } from 'estree-walker';
 import { is_head } from './shared/is_head';
 import { Identifier, Node } from 'estree';
-import { changed } from './shared/changed';
 
 function is_else_if(node: ElseBlock) {
 	return (
@@ -267,12 +266,12 @@ export default class IfBlockWrapper extends Wrapper {
 		/* eslint-disable @typescript-eslint/indent,indent */
 		if (this.needs_update) {
 			block.chunks.init.push(b`
-				function ${select_block_type}(#changed, #ctx) {
+				function ${select_block_type}(#ctx, #dirty) {
 					${this.branches.map(({ dependencies, condition, snippet, block }) => condition
 					? b`
 					${snippet && (
 						dependencies.length > 0
-							? b`if (${condition} == null || ${changed(dependencies)}) ${condition} = !!${snippet}`
+							? b`if (${condition} == null || ${block.renderer.dirty(dependencies)}) ${condition} = !!${snippet}`
 							: b`if (${condition} == null) ${condition} = !!${snippet}`
 					)}
 					if (${condition}) return ${block.name};`
@@ -281,7 +280,7 @@ export default class IfBlockWrapper extends Wrapper {
 			`);
 		} else {
 			block.chunks.init.push(b`
-				function ${select_block_type}(#changed, #ctx) {
+				function ${select_block_type}(#ctx, #dirty) {
 					${this.branches.map(({ condition, snippet, block }) => condition
 					? b`if (${snippet || condition}) return ${block.name};`
 					: b`return ${block.name};`)}
@@ -291,7 +290,7 @@ export default class IfBlockWrapper extends Wrapper {
 		/* eslint-enable @typescript-eslint/indent,indent */
 
 		block.chunks.init.push(b`
-			let ${current_block_type} = ${select_block_type}(null, #ctx);
+			let ${current_block_type} = ${select_block_type}(#ctx, -1);
 			let ${name} = ${get_block};
 		`);
 
@@ -323,21 +322,21 @@ export default class IfBlockWrapper extends Wrapper {
 
 			if (dynamic) {
 				block.chunks.update.push(b`
-					if (${current_block_type} === (${current_block_type} = ${select_block_type}(#changed, #ctx)) && ${name}) {
-						${name}.p(#changed, #ctx);
+					if (${current_block_type} === (${current_block_type} = ${select_block_type}(#ctx, #dirty)) && ${name}) {
+						${name}.p(#ctx, #dirty);
 					} else {
 						${change_block}
 					}
 				`);
 			} else {
 				block.chunks.update.push(b`
-					if (${current_block_type} !== (${current_block_type} = ${select_block_type}(#changed, #ctx))) {
+					if (${current_block_type} !== (${current_block_type} = ${select_block_type}(#ctx, #dirty))) {
 						${change_block}
 					}
 				`);
 			}
 		} else if (dynamic) {
-			block.chunks.update.push(b`${name}.p(#changed, #ctx);`);
+			block.chunks.update.push(b`${name}.p(#ctx, #dirty);`);
 		}
 
 		if (if_exists_condition) {
@@ -386,13 +385,13 @@ export default class IfBlockWrapper extends Wrapper {
 
 			${this.needs_update
 				? b`
-					function ${select_block_type}(#changed, #ctx) {
+					function ${select_block_type}(#ctx, #dirty) {
 						${this.branches.map(({ dependencies, condition, snippet }, i) => condition
 						? b`
 						${snippet && (
 							dependencies.length > 0
-								? b`if (${condition} == null || ${changed(dependencies)}) ${condition} = !!${snippet}`
-								: b`if (${condition} == null) ${condition} = !!${snippet}`
+								? b`if (${block.renderer.dirty(dependencies)}) ${condition} = !!${snippet}`
+								: b`if (${condition} == -1) ${condition} = !!${snippet}`
 						)}
 						if (${condition}) return ${i};`
 						: b`return ${i};`)}
@@ -400,7 +399,7 @@ export default class IfBlockWrapper extends Wrapper {
 					}
 				`
 				: b`
-					function ${select_block_type}(#changed, #ctx) {
+					function ${select_block_type}(#ctx, #dirty) {
 						${this.branches.map(({ condition, snippet }, i) => condition
 						? b`if (${snippet || condition}) return ${i};`
 						: b`return ${i};`)}
@@ -412,12 +411,12 @@ export default class IfBlockWrapper extends Wrapper {
 
 		if (has_else) {
 			block.chunks.init.push(b`
-				${current_block_type_index} = ${select_block_type}(null, #ctx);
+				${current_block_type_index} = ${select_block_type}(#ctx, -1);
 				${name} = ${if_blocks}[${current_block_type_index}] = ${if_block_creators}[${current_block_type_index}](#ctx);
 			`);
 		} else {
 			block.chunks.init.push(b`
-				if (~(${current_block_type_index} = ${select_block_type}(null, #ctx))) {
+				if (~(${current_block_type_index} = ${select_block_type}(#ctx, -1))) {
 					${name} = ${if_blocks}[${current_block_type_index}] = ${if_block_creators}[${current_block_type_index}](#ctx);
 				}
 			`);
@@ -474,9 +473,9 @@ export default class IfBlockWrapper extends Wrapper {
 			if (dynamic) {
 				block.chunks.update.push(b`
 					let ${previous_block_index} = ${current_block_type_index};
-					${current_block_type_index} = ${select_block_type}(#changed, #ctx);
+					${current_block_type_index} = ${select_block_type}(#ctx, #dirty);
 					if (${current_block_type_index} === ${previous_block_index}) {
-						${if_current_block_type_index(b`${if_blocks}[${current_block_type_index}].p(#changed, #ctx);`)}
+						${if_current_block_type_index(b`${if_blocks}[${current_block_type_index}].p(#ctx, #dirty);`)}
 					} else {
 						${change_block}
 					}
@@ -484,14 +483,14 @@ export default class IfBlockWrapper extends Wrapper {
 			} else {
 				block.chunks.update.push(b`
 					let ${previous_block_index} = ${current_block_type_index};
-					${current_block_type_index} = ${select_block_type}(#changed, #ctx);
+					${current_block_type_index} = ${select_block_type}(#ctx, #dirty);
 					if (${current_block_type_index} !== ${previous_block_index}) {
 						${change_block}
 					}
 				`);
 			}
 		} else if (dynamic) {
-			block.chunks.update.push(b`${name}.p(#changed, #ctx);`);
+			block.chunks.update.push(b`${name}.p(#ctx, #dirty);`);
 		}
 
 		block.chunks.destroy.push(
@@ -528,7 +527,7 @@ export default class IfBlockWrapper extends Wrapper {
 			const enter = dynamic
 				? b`
 					if (${name}) {
-						${name}.p(#changed, #ctx);
+						${name}.p(#ctx, #dirty);
 						${has_transitions && b`@transition_in(${name}, 1);`}
 					} else {
 						${name} = ${branch.block.name}(#ctx);
@@ -549,7 +548,7 @@ export default class IfBlockWrapper extends Wrapper {
 				`;
 
 			if (branch.snippet) {
-				block.chunks.update.push(b`if (${changed(branch.dependencies)}) ${branch.condition} = ${branch.snippet}`);
+				block.chunks.update.push(b`if (${block.renderer.dirty(branch.dependencies)}) ${branch.condition} = ${branch.snippet}`);
 			}
 
 			// no `p()` here — we don't want to update outroing nodes,
@@ -578,7 +577,7 @@ export default class IfBlockWrapper extends Wrapper {
 			}
 		} else if (dynamic) {
 			block.chunks.update.push(b`
-				if (${branch.condition}) ${name}.p(#changed, #ctx);
+				if (${branch.condition}) ${name}.p(#ctx, #dirty);
 			`);
 		}
 

src/compiler/compile/render_dom/wrappers/InlineComponent/index.ts

@@ -9,18 +9,18 @@ import { b, x, p } from 'code-red';
 import Attribute from '../../../nodes/Attribute';
 import get_object from '../../../utils/get_object';
 import create_debugging_comment from '../shared/create_debugging_comment';
-import { get_context_merger } from '../shared/get_context_merger';
+import { get_slot_definition } from '../shared/get_slot_definition';
 import EachBlock from '../../../nodes/EachBlock';
 import TemplateScope from '../../../nodes/shared/TemplateScope';
 import is_dynamic from '../shared/is_dynamic';
 import bind_this from '../shared/bind_this';
-import { changed } from '../shared/changed';
 import { Node, Identifier, ObjectExpression } from 'estree';
 import EventHandler from '../Element/EventHandler';
+import { extract_names } from 'periscopic';
 
 export default class InlineComponentWrapper extends Wrapper {
 	var: Identifier;
-	slots: Map<string, { block: Block; scope: TemplateScope; fn?: Node }> = new Map();
+	slots: Map<string, { block: Block; scope: TemplateScope; get_context?: Node; get_changes?: Node }> = new Map();
 	node: InlineComponent;
 	fragment: FragmentWrapper;
 
@@ -74,6 +74,12 @@ export default class InlineComponentWrapper extends Wrapper {
 		};
 
 		if (this.node.children.length) {
+			this.node.lets.forEach(l => {
+				extract_names(l.value || l.name).forEach(name => {
+					renderer.add_to_context(name, true);
+				});
+			});
+
 			const default_slot = block.child({
 				comment: create_debugging_comment(node, renderer.component),
 				name: renderer.component.get_unique_name(`create_default_slot`),
@@ -82,13 +88,7 @@ export default class InlineComponentWrapper extends Wrapper {
 
 			this.renderer.blocks.push(default_slot);
 
-			const fn = get_context_merger(this.node.lets);
-
-			this.slots.set('default', {
-				block: default_slot,
-				scope: this.node.scope,
-				fn
-			});
+			this.slots.set('default', get_slot_definition(default_slot, this.node.scope, this.node.lets));
 			this.fragment = new FragmentWrapper(renderer, default_slot, node.children, this, strip_whitespace, next_sibling);
 
 			const dependencies: Set<string> = new Set();
@@ -130,7 +130,7 @@ export default class InlineComponentWrapper extends Wrapper {
 			? [
 				p`$$slots: {
 					${Array.from(this.slots).map(([name, slot]) => {
-						return p`${name}: [${slot.block.name}, ${slot.fn || null}]`;
+						return p`${name}: [${slot.block.name}, ${slot.get_context || null}, ${slot.get_changes || null}]`;
 					})}
 				}`,
 				p`$$scope: {
@@ -156,6 +156,7 @@ export default class InlineComponentWrapper extends Wrapper {
 		}
 
 		if (this.fragment) {
+			this.renderer.add_to_context('$$scope', true);
 			const default_slot = this.slots.get('default');
 
 			this.fragment.nodes.forEach((child) => {
@@ -206,7 +207,7 @@ export default class InlineComponentWrapper extends Wrapper {
 					const { name, dependencies } = attr;
 
 					const condition = dependencies.size > 0 && (dependencies.size !== all_dependencies.size)
-						? changed(Array.from(dependencies))
+						? renderer.dirty(Array.from(dependencies))
 						: null;
 
 					if (attr.is_spread) {
@@ -239,7 +240,7 @@ export default class InlineComponentWrapper extends Wrapper {
 				`);
 
 				if (all_dependencies.size) {
-					const condition = changed(Array.from(all_dependencies));
+					const condition = renderer.dirty(Array.from(all_dependencies));
 
 					updates.push(b`
 						const ${name_changes} = ${condition} ? @get_spread_update(${levels}, [
@@ -255,7 +256,7 @@ export default class InlineComponentWrapper extends Wrapper {
 				dynamic_attributes.forEach((attribute: Attribute) => {
 					const dependencies = attribute.get_dependencies();
 					if (dependencies.length > 0) {
-						const condition = changed(dependencies);
+						const condition = renderer.dirty(dependencies);
 
 						updates.push(b`
 							if (${condition}) ${name_changes}.${attribute.name} = ${attribute.get_value(block)};
@@ -267,8 +268,8 @@ export default class InlineComponentWrapper extends Wrapper {
 
 		if (non_let_dependencies.length > 0) {
 			updates.push(b`
-				if (${changed(non_let_dependencies)}) {
-					${name_changes}.$$scope = { changed: #changed, ctx: #ctx };
+				if (${renderer.dirty(non_let_dependencies)}) {
+					${name_changes}.$$scope = { dirty: #dirty, ctx: #ctx };
 				}`);
 		}
 
@@ -280,12 +281,8 @@ export default class InlineComponentWrapper extends Wrapper {
 			}
 
 			const id = component.get_unique_name(`${this.var.name}_${binding.name}_binding`);
-
-			component.add_var({
-				name: id.name,
-				internal: true,
-				referenced: true
-			});
+			renderer.add_to_context(id.name);
+			const callee = renderer.reference(id);
 
 			const updating = block.get_unique_name(`updating_${binding.name}`);
 			block.add_variable(updating);
@@ -299,7 +296,7 @@ export default class InlineComponentWrapper extends Wrapper {
 			);
 
 			updates.push(b`
-				if (!${updating} && ${changed(Array.from(binding.expression.dependencies))}) {
+				if (!${updating} && ${renderer.dirty(Array.from(binding.expression.dependencies))}) {
 					${updating} = true;
 					${name_changes}.${binding.name} = ${snippet};
 					@add_flush_callback(() => ${updating} = false);
@@ -321,24 +318,24 @@ export default class InlineComponentWrapper extends Wrapper {
 			}
 
 			const value = block.get_unique_name('value');
-			const args: any[] = [value];
+			const params: any[] = [value];
 			if (contextual_dependencies.length > 0) {
-				args.push({
-					type: 'ObjectPattern',
-					properties: contextual_dependencies.map(name => {
-						const id = { type: 'Identifier', name };
-						return {
-							type: 'Property',
-							kind: 'init',
-							key: id,
-							value: id
-						};
-					})
+				const args = [];
+
+				contextual_dependencies.forEach(name => {
+					params.push({
+						type: 'Identifier',
+						name
+					});
+
+					renderer.add_to_context(name, true);
+					args.push(renderer.reference(name));
 				});
 
+
 				block.chunks.init.push(b`
 					function ${id}(${value}) {
-						#ctx.${id}.call(null, ${value}, #ctx);
+						${callee}.call(null, ${value}, ${args});
 					}
 				`);
 
@@ -346,15 +343,15 @@ export default class InlineComponentWrapper extends Wrapper {
 			} else {
 				block.chunks.init.push(b`
 					function ${id}(${value}) {
-						#ctx.${id}.call(null, ${value});
+						${callee}.call(null, ${value});
 					}
 				`);
 			}
 
 			const body = b`
-				function ${id}(${args}) {
+				function ${id}(${params}) {
 					${lhs} = ${value};
-					${component.invalidate(dependencies[0])};
+					${renderer.invalidate(dependencies[0])};
 				}
 			`;
 
@@ -460,7 +457,7 @@ export default class InlineComponentWrapper extends Wrapper {
 		} else {
 			const expression = this.node.name === 'svelte:self'
 				? component.name
-				: component.qualify(this.node.name);
+				: this.renderer.reference(this.node.name);
 
 			block.chunks.init.push(b`
 				${(this.node.attributes.length > 0 || this.node.bindings.length > 0) && b`

src/compiler/compile/render_dom/wrappers/Slot.ts

@@ -6,11 +6,39 @@ import FragmentWrapper from './Fragment';
 import { b, p, x } from 'code-red';
 import { sanitize } from '../../../utils/names';
 import add_to_set from '../../utils/add_to_set';
-import get_slot_data from '../../utils/get_slot_data';
 import Expression from '../../nodes/shared/Expression';
 import is_dynamic from './shared/is_dynamic';
 import { Identifier, ObjectExpression } from 'estree';
-import { changed } from './shared/changed';
+import Attribute from '../../nodes/Attribute';
+import { string_literal } from '../../utils/stringify';
+
+function get_slot_data(block: Block, values: Map<string, Attribute>) {
+	return {
+		type: 'ObjectExpression',
+		properties: Array.from(values.values())
+			.filter(attribute => attribute.name !== 'name')
+			.map(attribute => {
+				const value = get_value(block, attribute);
+				return p`${attribute.name}: ${value}`;
+			})
+	};
+}
+
+// TODO fairly sure this is duplicated at least once
+function get_value(block: Block, attribute: Attribute) {
+	if (attribute.is_true) return x`true`;
+	if (attribute.chunks.length === 0) return x`""`;
+
+	let value = attribute.chunks
+		.map(chunk => chunk.type === 'Text' ? string_literal(chunk.data) : chunk.manipulate(block))
+		.reduce((lhs, rhs) => x`${lhs} + ${rhs}`);
+
+	if (attribute.chunks.length > 1 && attribute.chunks[0].type !== 'Text') {
+		value = x`"" + ${value}`;
+	}
+
+	return value;
+}
 
 export default class SlotWrapper extends Wrapper {
 	node: Slot;
@@ -60,14 +88,13 @@ export default class SlotWrapper extends Wrapper {
 
 		const { slot_name } = this.node;
 
-		let get_slot_changes;
-		let get_slot_context;
+		let get_slot_changes_fn;
+		let get_slot_context_fn;
 
 		if (this.node.values.size > 0) {
-			get_slot_changes = renderer.component.get_unique_name(`get_${sanitize(slot_name)}_slot_changes`);
-			get_slot_context = renderer.component.get_unique_name(`get_${sanitize(slot_name)}_slot_context`);
+			get_slot_changes_fn = renderer.component.get_unique_name(`get_${sanitize(slot_name)}_slot_changes`);
+			get_slot_context_fn = renderer.component.get_unique_name(`get_${sanitize(slot_name)}_slot_context`);
 
-			const context = get_slot_data(this.node.values);
 			const changes = x`{}` as ObjectExpression;
 
 			const dependencies = new Set();
@@ -92,34 +119,25 @@ export default class SlotWrapper extends Wrapper {
 				});
 
 				if (dynamic_dependencies.length > 0) {
-					const expression = dynamic_dependencies
-						.map(name => ({ type: 'Identifier', name } as any))
-						.reduce((lhs, rhs) => x`${lhs} || ${rhs}`);
-
-					changes.properties.push(p`${attribute.name}: ${expression}`);
+					changes.properties.push(p`${attribute.name}: ${renderer.dirty(dynamic_dependencies)}`);
 				}
 			});
 
-			const arg = dependencies.size > 0 && {
-				type: 'ObjectPattern',
-				properties: Array.from(dependencies).map(name => p`${name}`)
-			};
-
 			renderer.blocks.push(b`
-				const ${get_slot_changes} = (${arg}) => (${changes});
-				const ${get_slot_context} = (${arg}) => (${context});
+				const ${get_slot_changes_fn} = #dirty => ${changes};
+				const ${get_slot_context_fn} = #ctx => ${get_slot_data(block, this.node.values)};
 			`);
 		} else {
-			get_slot_changes = 'null';
-			get_slot_context = 'null';
+			get_slot_changes_fn = 'null';
+			get_slot_context_fn = 'null';
 		}
 
 		const slot = block.get_unique_name(`${sanitize(slot_name)}_slot`);
 		const slot_definition = block.get_unique_name(`${sanitize(slot_name)}_slot_template`);
 
 		block.chunks.init.push(b`
-			const ${slot_definition} = #ctx.$$slots.${slot_name};
-			const ${slot} = @create_slot(${slot_definition}, #ctx, ${get_slot_context});
+			const ${slot_definition} = ${renderer.reference('$$slots')}.${slot_name};
+			const ${slot} = @create_slot(${slot_definition}, #ctx, ${renderer.reference('$$scope')}, ${get_slot_context_fn});
 		`);
 
 		// TODO this is a dreadful hack! Should probably make this nicer
@@ -184,10 +202,10 @@ export default class SlotWrapper extends Wrapper {
 		});
 
 		block.chunks.update.push(b`
-			if (${slot} && ${slot}.p && ${changed(dynamic_dependencies)}) {
+			if (${slot} && ${slot}.p && ${renderer.dirty(dynamic_dependencies)}) {
 				${slot}.p(
-					@get_slot_changes(${slot_definition}, #ctx, #changed, ${get_slot_changes}),
-					@get_slot_context(${slot_definition}, #ctx, ${get_slot_context})
+					@get_slot_context(${slot_definition}, #ctx, ${renderer.reference('$$scope')}, ${get_slot_context_fn}),
+					@get_slot_changes(${slot_definition}, ${renderer.reference('$$scope')}, #dirty, ${get_slot_changes_fn})
 				);
 			}
 		`);

src/compiler/compile/render_dom/wrappers/Title.ts

@@ -7,7 +7,6 @@ import { string_literal } from '../../utils/stringify';
 import add_to_set from '../../utils/add_to_set';
 import Text from '../../nodes/Text';
 import { Identifier } from 'estree';
-import { changed } from './shared/changed';
 import MustacheTag from '../../nodes/MustacheTag';
 
 export default class TitleWrapper extends Wrapper {
@@ -76,7 +75,7 @@ export default class TitleWrapper extends Wrapper {
 			if (all_dependencies.size) {
 				const dependencies = Array.from(all_dependencies);
 
-				let condition = changed(dependencies);
+				let condition = block.renderer.dirty(dependencies);
 
 				if (block.has_outros) {
 					condition = x`!#current || ${condition}`;

src/compiler/compile/render_dom/wrappers/Window.ts

@@ -5,7 +5,6 @@ import { b, x } from 'code-red';
 import add_event_handlers from './shared/add_event_handlers';
 import Window from '../../nodes/Window';
 import add_actions from './shared/add_actions';
-import { changed } from './shared/changed';
 import { Identifier } from 'estree';
 import { TemplateNode } from '../../../interfaces';
 import EventHandler from './Element/EventHandler';
@@ -49,7 +48,7 @@ export default class WindowWrapper extends Wrapper {
 		const events = {};
 		const bindings: Record<string, string> = {};
 
-		add_actions(component, block, '@_window', this.node.actions);
+		add_actions(block, '@_window', this.node.actions);
 		add_event_handlers(block, '@_window', this.handlers);
 
 		this.node.bindings.forEach(binding => {
@@ -81,6 +80,9 @@ export default class WindowWrapper extends Wrapper {
 			const id = block.get_unique_name(`onwindow${event}`);
 			const props = events[event];
 
+			renderer.add_to_context(id.name);
+			const fn = renderer.reference(id.name);
+
 			if (event === 'scroll') {
 				// TODO other bidirectional bindings...
 				block.add_variable(scrolling, x`false`);
@@ -107,7 +109,7 @@ export default class WindowWrapper extends Wrapper {
 						${scrolling} = true;
 						@_clearTimeout(${scrolling_timeout});
 						${scrolling_timeout} = @_setTimeout(${clear_scrolling}, 100);
-						#ctx.${id}();
+						${fn}();
 					})
 				`);
 			} else {
@@ -118,24 +120,18 @@ export default class WindowWrapper extends Wrapper {
 				});
 
 				block.event_listeners.push(x`
-					@listen(@_window, "${event}", #ctx.${id})
+					@listen(@_window, "${event}", ${fn})
 				`);
 			}
 
-			component.add_var({
-				name: id.name,
-				internal: true,
-				referenced: true
-			});
-
 			component.partly_hoisted.push(b`
 				function ${id}() {
-					${props.map(prop => component.invalidate(prop.name, x`${prop.name} = @_window.${prop.value}`))}
+					${props.map(prop => renderer.invalidate(prop.name, x`${prop.name} = @_window.${prop.value}`))}
 				}
 			`);
 
 			block.chunks.init.push(b`
-				@add_render_callback(#ctx.${id});
+				@add_render_callback(${fn});
 			`);
 
 			component.has_reactive_assignments = true;
@@ -143,9 +139,10 @@ export default class WindowWrapper extends Wrapper {
 
 		// special case... might need to abstract this out if we add more special cases
 		if (bindings.scrollX || bindings.scrollY) {
-			const condition = changed([bindings.scrollX, bindings.scrollY].filter(Boolean));
-			const scrollX = bindings.scrollX ? x`#ctx.${bindings.scrollX}` : x`@_window.pageXOffset`;
-			const scrollY = bindings.scrollY ? x`#ctx.${bindings.scrollY}` : x`@_window.pageYOffset`;
+			const condition = renderer.dirty([bindings.scrollX, bindings.scrollY].filter(Boolean));
+
+			const scrollX = bindings.scrollX ? renderer.reference(bindings.scrollX) : x`@_window.pageXOffset`;
+			const scrollY = bindings.scrollY ? renderer.reference(bindings.scrollY) : x`@_window.pageYOffset`;
 
 			block.chunks.update.push(b`
 				if (${condition} && !${scrolling}) {
@@ -162,25 +159,22 @@ export default class WindowWrapper extends Wrapper {
 			const id = block.get_unique_name(`onlinestatuschanged`);
 			const name = bindings.online;
 
-			component.add_var({
-				name: id.name,
-				internal: true,
-				referenced: true
-			});
+			renderer.add_to_context(id.name);
+			const reference = renderer.reference(id.name);
 
 			component.partly_hoisted.push(b`
 				function ${id}() {
-					${component.invalidate(name, x`${name} = @_navigator.onLine`)}
+					${renderer.invalidate(name, x`${name} = @_navigator.onLine`)}
 				}
 			`);
 
 			block.chunks.init.push(b`
-				@add_render_callback(#ctx.${id});
+				@add_render_callback(${reference});
 			`);
 
 			block.event_listeners.push(
-				x`@listen(@_window, "online", #ctx.${id})`,
-				x`@listen(@_window, "offline", #ctx.${id})`
+				x`@listen(@_window, "online", ${reference})`,
+				x`@listen(@_window, "offline", ${reference})`
 			);
 
 			component.has_reactive_assignments = true;

src/compiler/compile/render_dom/wrappers/shared/Tag.ts

@@ -5,7 +5,6 @@ import Block from '../../Block';
 import MustacheTag from '../../../nodes/MustacheTag';
 import RawMustacheTag from '../../../nodes/RawMustacheTag';
 import { Node } from 'estree';
-import { changed } from './changed';
 
 export default class Tag extends Wrapper {
 	node: MustacheTag | RawMustacheTag;
@@ -40,7 +39,7 @@ export default class Tag extends Wrapper {
 		if (this.node.should_cache) block.add_variable(value, snippet); // TODO may need to coerce snippet to string
 
 		if (dependencies.length > 0) {
-			let condition = changed(dependencies);
+			let condition = block.renderer.dirty(dependencies);
 
 			if (block.has_outros) {
 				condition = x`!#current || ${condition}`;

src/compiler/compile/render_dom/wrappers/shared/add_actions.ts

@@ -1,10 +1,8 @@
 import { b, x } from 'code-red';
 import Block from '../../Block';
 import Action from '../../../nodes/Action';
-import Component from '../../../Component';
 
 export default function add_actions(
-	component: Component,
 	block: Block,
 	target: string,
 	actions: Action[]
@@ -25,7 +23,7 @@ export default function add_actions(
 
 		block.add_variable(id);
 
-		const fn = component.qualify(action.name);
+		const fn = block.renderer.reference(action.name);
 
 		block.chunks.mount.push(
 			b`${id} = ${fn}.call(null, ${target}, ${snippet}) || {};`
@@ -34,14 +32,8 @@ export default function add_actions(
 		if (dependencies && dependencies.length > 0) {
 			let condition = x`@is_function(${id}.update)`;
 
-			// TODO can this case be handled more elegantly?
 			if (dependencies.length > 0) {
-				let changed = x`#changed.${dependencies[0]}`;
-				for (let i = 1; i < dependencies.length; i += 1) {
-					changed = x`${changed} || #changed.${dependencies[i]}`;
-				}
-
-				condition = x`${condition} && ${changed}`;
+				condition = x`${condition} && ${block.renderer.dirty(dependencies)}`;
 			}
 
 			block.chunks.update.push(

src/compiler/compile/render_dom/wrappers/shared/bind_this.ts

@@ -8,11 +8,8 @@ import { Identifier } from 'estree';
 export default function bind_this(component: Component, block: Block, binding: Binding, variable: Identifier) {
 	const fn = component.get_unique_name(`${variable.name}_binding`);
 
-	component.add_var({
-		name: fn.name,
-		internal: true,
-		referenced: true
-	});
+	block.renderer.add_to_context(fn.name);
+	const callee = block.renderer.reference(fn.name);
 
 	let lhs;
 	let object;
@@ -32,11 +29,11 @@ export default function bind_this(component: Component, block: Block, binding: B
 
 		body = binding.raw_expression.type === 'Identifier'
 			? b`
-				${component.invalidate(object, x`${lhs} = $$value`)};
+				${block.renderer.invalidate(object, x`${lhs} = $$value`)};
 			`
 			: b`
 				${lhs} = $$value;
-				${component.invalidate(object)};
+				${block.renderer.invalidate(object)};
 			`;
 	}
 
@@ -58,19 +55,19 @@ export default function bind_this(component: Component, block: Block, binding: B
 		const args = [];
 		for (const id of contextual_dependencies) {
 			args.push(id);
-			block.add_variable(id, x`#ctx.${id}`);
+			block.add_variable(id, block.renderer.reference(id.name));
 		}
 
 		const assign = block.get_unique_name(`assign_${variable.name}`);
 		const unassign = block.get_unique_name(`unassign_${variable.name}`);
 
 		block.chunks.init.push(b`
-			const ${assign} = () => #ctx.${fn}(${variable}, ${args});
-			const ${unassign} = () => #ctx.${fn}(null, ${args});
+			const ${assign} = () => ${callee}(${variable}, ${args});
+			const ${unassign} = () => ${callee}(null, ${args});
 		`);
 
 		const condition = Array.from(contextual_dependencies)
-			.map(name => x`${name} !== #ctx.${name}`)
+			.map(name => x`${name} !== ${block.renderer.reference(name.name)}`)
 			.reduce((lhs, rhs) => x`${lhs} || ${rhs}`);
 
 		// we push unassign and unshift assign so that references are
@@ -79,7 +76,7 @@ export default function bind_this(component: Component, block: Block, binding: B
 		block.chunks.update.push(b`
 			if (${condition}) {
 				${unassign}();
-				${args.map(a => b`${a} = #ctx.${a}`)};
+				${args.map(a => b`${a} = ${block.renderer.reference(a.name)}`)};
 				${assign}();
 			}`
 		);
@@ -96,6 +93,6 @@ export default function bind_this(component: Component, block: Block, binding: B
 		}
 	`);
 
-	block.chunks.destroy.push(b`#ctx.${fn}(null);`);
-	return b`#ctx.${fn}(${variable});`;
+	block.chunks.destroy.push(b`${callee}(null);`);
+	return b`${callee}(${variable});`;
 }

src/compiler/compile/render_dom/wrappers/shared/changed.ts

@@ -1,7 +0,0 @@
-import { x } from 'code-red';
-
-export function changed(dependencies: string[]) {
-	return dependencies
-		.map(d => x`#changed.${d}`)
-		.reduce((lhs, rhs) => x`${lhs} || ${rhs}`);
-}

src/compiler/compile/render_dom/wrappers/shared/get_context_merger.ts

@@ -1,39 +0,0 @@
-import Let from '../../../nodes/Let';
-import { x } from 'code-red';
-
-export function get_context_merger(lets: Let[]) {
-	if (lets.length === 0) return null;
-
-	const input = {
-		type: 'ObjectPattern',
-		properties: lets.map(l => ({
-			type: 'Property',
-			kind: 'init',
-			key: l.name,
-			value: l.value || l.name
-		}))
-	};
-
-	const names = new Set();
-	lets.forEach(l => {
-		l.names.forEach(name => {
-			names.add(name);
-		});
-	});
-
-	const output = {
-		type: 'ObjectExpression',
-		properties: Array.from(names).map(name => {
-			const id = { type: 'Identifier', name };
-
-			return {
-				type: 'Property',
-				kind: 'init',
-				key: id,
-				value: id
-			};
-		})
-	};
-
-	return x`(${input}) => (${output})`;
-}

src/compiler/compile/render_dom/wrappers/shared/get_slot_definition.ts

@@ -0,0 +1,53 @@
+import Let from '../../../nodes/Let';
+import { x, p } from 'code-red';
+import Block from '../../Block';
+import TemplateScope from '../../../nodes/shared/TemplateScope';
+
+export function get_slot_definition(block: Block, scope: TemplateScope, lets: Let[]) {
+	if (lets.length === 0) return { block, scope };
+
+	const input = {
+		type: 'ObjectPattern',
+		properties: lets.map(l => ({
+			type: 'Property',
+			kind: 'init',
+			key: l.name,
+			value: l.value || l.name
+		}))
+	};
+
+	const names: Set<string> = new Set();
+	lets.forEach(l => {
+		l.names.forEach(name => {
+			names.add(name);
+		});
+	});
+
+	const context = {
+		type: 'ObjectExpression',
+		properties: Array.from(names).map(name => p`${block.renderer.context_lookup.get(name).index}: ${name}`)
+	};
+
+	const changes = Array.from(names)
+		.map(name => {
+			const { context_lookup } = block.renderer;
+
+			const literal = {
+				type: 'Literal',
+				get value() {
+					const i = context_lookup.get(name).index.value as number;
+					return 1 << i;
+				}
+			};
+
+			return x`${name} ? ${literal} : 0`;
+		})
+		.reduce((lhs, rhs) => x`${lhs} | ${rhs}`);
+
+	return {
+		block,
+		scope,
+		get_context: x`${input} => ${context}`,
+		get_changes: x`${input} => ${changes}`
+	};
+}

src/compiler/compile/render_ssr/handlers/Element.ts

@@ -30,7 +30,7 @@ export default function(node: Element, renderer: Renderer, options: RenderOption
 
 	const class_expression_list = node.classes.map(class_directive => {
 		const { expression, name } = class_directive;
-		const snippet = expression ? expression.node : x`#ctx.${name}`;
+		const snippet = expression ? expression.node : x`#ctx.${name}`; // TODO is this right?
 		return x`${snippet} ? "${name}" : ""`;
 	});
 	if (node.needs_manual_style_scoping) {

src/compiler/compile/render_ssr/handlers/Slot.ts

@@ -1,7 +1,37 @@
-import get_slot_data from '../../utils/get_slot_data';
 import Renderer, { RenderOptions } from '../Renderer';
 import Slot from '../../nodes/Slot';
-import { x } from 'code-red';
+import { x, p } from 'code-red';
+import Attribute from '../../nodes/Attribute';
+import { string_literal } from '../../utils/stringify';
+
+// TODO this is *almost* but not quite duplicated with non-SSR
+function get_slot_data(values: Map<string, Attribute>) {
+	return {
+		type: 'ObjectExpression',
+		properties: Array.from(values.values())
+			.filter(attribute => attribute.name !== 'name')
+			.map(attribute => {
+				const value = get_value(attribute);
+				return p`${attribute.name}: ${value}`;
+			})
+	};
+}
+
+// TODO fairly sure this is duplicated at least once
+function get_value(attribute: Attribute) {
+	if (attribute.is_true) return x`true`;
+	if (attribute.chunks.length === 0) return x`""`;
+
+	let value = attribute.chunks
+		.map(chunk => chunk.type === 'Text' ? string_literal(chunk.data) : chunk.node)
+		.reduce((lhs, rhs) => x`${lhs} + ${rhs}`);
+
+	if (attribute.chunks.length > 1 && attribute.chunks[0].type !== 'Text') {
+		value = x`"" + ${value}`;
+	}
+
+	return value;
+}
 
 export default function(node: Slot, renderer: Renderer, options: RenderOptions) {
 	const slot_data = get_slot_data(node.values);

src/compiler/compile/utils/get_slot_data.ts

@@ -1,26 +1,27 @@
 import Attribute from '../nodes/Attribute';
 import { p, x } from 'code-red';
 import { string_literal } from './stringify';
+import Block from '../render_dom/Block';
 
-export default function get_slot_data(values: Map<string, Attribute>) {
+export default function get_slot_data(block: Block, values: Map<string, Attribute>) {
 	return {
 		type: 'ObjectExpression',
 		properties: Array.from(values.values())
 			.filter(attribute => attribute.name !== 'name')
 			.map(attribute => {
-				const value = get_value(attribute);
+				const value = get_value(block, attribute);
 				return p`${attribute.name}: ${value}`;
 			})
 	};
 }
 
 // TODO fairly sure this is duplicated at least once
-function get_value(attribute: Attribute) {
+function get_value(block: Block, attribute: Attribute) {
 	if (attribute.is_true) return x`true`;
 	if (attribute.chunks.length === 0) return x`""`;
 
 	let value = attribute.chunks
-		.map(chunk => chunk.type === 'Text' ? string_literal(chunk.data) : chunk.node)
+		.map(chunk => chunk.type === 'Text' ? string_literal(chunk.data) : chunk.manipulate(block))
 		.reduce((lhs, rhs) => x`${lhs} + ${rhs}`);
 
 	if (attribute.chunks.length > 1 && attribute.chunks[0].type !== 'Text') {

src/runtime/internal/Component.ts

@@ -1,6 +1,6 @@
 import { add_render_callback, flush, schedule_update, dirty_components } from './scheduler';
 import { current_component, set_current_component } from './lifecycle';
-import { blank_object, is_function, run, run_all, noop, has_prop } from './utils';
+import { blank_object, is_function, run, run_all, noop } from './utils';
 import { children } from './dom';
 import { transition_in } from './transitions';
 
@@ -11,7 +11,7 @@ interface Fragment {
 	/* claim   */ l: (nodes: any) => void;
 	/* hydrate */ h: () => void;
 	/* mount   */ m: (target: HTMLElement, anchor: any) => void;
-	/* update  */ p: (changed: any, ctx: any) => void;
+	/* update  */ p: (ctx: any, dirty: any) => void;
 	/* measure */ r: () => void;
 	/* fix     */ f: () => void;
 	/* animate */ a: () => void;
@@ -21,7 +21,7 @@ interface Fragment {
 }
 // eslint-disable-next-line @typescript-eslint/class-name-casing
 interface T$$ {
-	dirty: null;
+	dirty: number[];
 	ctx: null|any;
 	bound: any;
 	update: () => void;
@@ -37,10 +37,10 @@ interface T$$ {
 }
 
 export function bind(component, name, callback) {
-	if (has_prop(component.$$.props, name)) {
-		name = component.$$.props[name] || name;
-		component.$$.bound[name] = callback;
-		callback(component.$$.ctx[name]);
+	const index = component.$$.props[name];
+	if (index !== undefined) {
+		component.$$.bound[index] = callback;
+		callback(component.$$.ctx[index]);
 	}
 }
 
@@ -83,20 +83,20 @@ export function destroy_component(component, detaching) {
 		// TODO null out other refs, including component.$$ (but need to
 		// preserve final state?)
 		$$.on_destroy = $$.fragment = null;
-		$$.ctx = {};
+		$$.ctx = [];
 	}
 }
 
-function make_dirty(component, key) {
-	if (!component.$$.dirty) {
+function make_dirty(component, i) {
+	if (component.$$.dirty[0] === -1) {
 		dirty_components.push(component);
 		schedule_update();
-		component.$$.dirty = blank_object();
+		component.$$.dirty.fill(0);
 	}
-	component.$$.dirty[key] = true;
+	component.$$.dirty[(i / 31) | 0] |= (1 << (i % 31));
 }
 
-export function init(component, options, instance, create_fragment, not_equal, props) {
+export function init(component, options, instance, create_fragment, not_equal, props, dirty = [-1]) {
 	const parent_component = current_component;
 	set_current_component(component);
 
@@ -121,20 +121,20 @@ export function init(component, options, instance, create_fragment, not_equal, p
 
 		// everything else
 		callbacks: blank_object(),
-		dirty: null
+		dirty
 	};
 
 	let ready = false;
 
 	$$.ctx = instance
-		? instance(component, prop_values, (key, ret, value = ret) => {
-			if ($$.ctx && not_equal($$.ctx[key], $$.ctx[key] = value)) {
-				if ($$.bound[key]) $$.bound[key](value);
-				if (ready) make_dirty(component, key);
+		? instance(component, prop_values, (i, ret, value = ret) => {
+			if ($$.ctx && not_equal($$.ctx[i], $$.ctx[i] = value)) {
+				if ($$.bound[i]) $$.bound[i](value);
+				if (ready) make_dirty(component, i);
 			}
 			return ret;
 		})
-		: prop_values;
+		: [];
 
 	$$.update();
 	ready = true;

src/runtime/internal/await_block.ts

@@ -1,4 +1,4 @@
-import { assign, is_promise } from './utils';
+import { is_promise } from './utils';
 import { check_outros, group_outros, transition_in, transition_out } from './transitions';
 import { flush } from './scheduler';
 import { get_current_component, set_current_component } from './lifecycle';
@@ -9,9 +9,15 @@ export function handle_promise(promise, info) {
 	function update(type, index, key?, value?) {
 		if (info.token !== token) return;
 
-		info.resolved = key && { [key]: value };
+		info.resolved = value;
+
+		let child_ctx = info.ctx;
+
+		if (key !== undefined) {
+			child_ctx = child_ctx.slice();
+			child_ctx[key] = value;
+		}
 
-		const child_ctx = assign(assign({}, info.ctx), info.resolved);
 		const block = type && (info.current = type)(child_ctx);
 
 		let needs_flush = false;
@@ -69,6 +75,6 @@ export function handle_promise(promise, info) {
 			return true;
 		}
 
-		info.resolved = { [info.value]: promise };
+		info.resolved = promise;
 	}
 }

src/runtime/internal/keyed_each.ts

@@ -21,7 +21,7 @@ export function fix_and_outro_and_destroy_block(block, lookup) {
 	outro_and_destroy_block(block, lookup);
 }
 
-export function update_keyed_each(old_blocks, changed, get_key, dynamic, ctx, list, lookup, node, destroy, create_each_block, next, get_context) {
+export function update_keyed_each(old_blocks, dirty, get_key, dynamic, ctx, list, lookup, node, destroy, create_each_block, next, get_context) {
 	let o = old_blocks.length;
 	let n = list.length;
 
@@ -43,7 +43,7 @@ export function update_keyed_each(old_blocks, changed, get_key, dynamic, ctx, li
 			block = create_each_block(key, child_ctx);
 			block.c();
 		} else if (dynamic) {
-			block.p(changed, child_ctx);
+			block.p(child_ctx, dirty);
 		}
 
 		new_lookup.set(key, new_blocks[i] = block);

src/runtime/internal/scheduler.ts

@@ -71,10 +71,10 @@ export function flush() {
 
 function update($$) {
 	if ($$.fragment !== null) {
-		$$.update($$.dirty);
+		$$.update();
 		run_all($$.before_update);
-		$$.fragment && $$.fragment.p($$.dirty, $$.ctx);
-		$$.dirty = null;
+		$$.fragment && $$.fragment.p($$.ctx, $$.dirty);
+		$$.dirty = [-1];
 
 		$$.after_update.forEach(add_render_callback);
 	}

src/runtime/internal/utils.ts

@@ -63,23 +63,23 @@ export function component_subscribe(component, store, callback) {
 	component.$$.on_destroy.push(subscribe(store, callback));
 }
 
-export function create_slot(definition, ctx, fn) {
+export function create_slot(definition, ctx, $$scope, fn) {
 	if (definition) {
-		const slot_ctx = get_slot_context(definition, ctx, fn);
+		const slot_ctx = get_slot_context(definition, ctx, $$scope, fn);
 		return definition[0](slot_ctx);
 	}
 }
 
-export function get_slot_context(definition, ctx, fn) {
-	return definition[1]
-		? assign({}, assign(ctx.$$scope.ctx, definition[1](fn ? fn(ctx) : {})))
-		: ctx.$$scope.ctx;
+export function get_slot_context(definition, ctx, $$scope, fn) {
+	return definition[1] && fn
+		? assign($$scope.ctx.slice(), definition[1](fn(ctx)))
+		: $$scope.ctx;
 }
 
-export function get_slot_changes(definition, ctx, changed, fn) {
-	return definition[1]
-		? assign({}, assign(ctx.$$scope.changed || {}, definition[1](fn ? fn(changed) : {})))
-		: ctx.$$scope.changed || {};
+export function get_slot_changes(definition, $$scope, dirty, fn) {
+	return definition[2] && fn
+		? $$scope.dirty | definition[2](fn(dirty))
+		: $$scope.dirty;
 }
 
 export function exclude_internal_props(props) {

test/js/samples/action-custom-event-handler/expected.js

@@ -21,10 +21,10 @@ function create_fragment(ctx) {
 		},
 		m(target, anchor) {
 			insert(target, button, anchor);
-			foo_action = foo.call(null, button, ctx.foo_function) || ({});
+			foo_action = foo.call(null, button, /*foo_function*/ ctx[1]) || ({});
 		},
-		p(changed, ctx) {
-			if (is_function(foo_action.update) && changed.bar) foo_action.update.call(null, ctx.foo_function);
+		p(ctx, [dirty]) {
+			if (is_function(foo_action.update) && dirty & /*bar*/ 1) foo_action.update.call(null, /*foo_function*/ ctx[1]);
 		},
 		i: noop,
 		o: noop,
@@ -48,10 +48,10 @@ function instance($$self, $$props, $$invalidate) {
 	const foo_function = () => handleFoo(bar);
 
 	$$self.$set = $$props => {
-		if ("bar" in $$props) $$invalidate("bar", bar = $$props.bar);
+		if ("bar" in $$props) $$invalidate(0, bar = $$props.bar);
 	};
 
-	return { bar, foo_function };
+	return [bar, foo_function];
 }
 
 class Component extends SvelteComponent {

test/js/samples/bind-online/expected.js

@@ -11,13 +11,13 @@ import {
 
 function create_fragment(ctx) {
 	let dispose;
-	add_render_callback(ctx.onlinestatuschanged);
+	add_render_callback(/*onlinestatuschanged*/ ctx[1]);
 
 	return {
 		c() {
 			dispose = [
-				listen(window, "online", ctx.onlinestatuschanged),
-				listen(window, "offline", ctx.onlinestatuschanged)
+				listen(window, "online", /*onlinestatuschanged*/ ctx[1]),
+				listen(window, "offline", /*onlinestatuschanged*/ ctx[1])
 			];
 		},
 		m: noop,
@@ -34,10 +34,10 @@ function instance($$self, $$props, $$invalidate) {
 	let online;
 
 	function onlinestatuschanged() {
-		$$invalidate("online", online = navigator.onLine);
+		$$invalidate(0, online = navigator.onLine);
 	}
 
-	return { online, onlinestatuschanged };
+	return [online, onlinestatuschanged];
 }
 
 class Component extends SvelteComponent {

test/js/samples/bind-open/expected.js

@@ -21,15 +21,15 @@ function create_fragment(ctx) {
 			details.innerHTML = `<summary>summary</summary>content
 `;
 
-			dispose = listen(details, "toggle", ctx.details_toggle_handler);
+			dispose = listen(details, "toggle", /*details_toggle_handler*/ ctx[1]);
 		},
 		m(target, anchor) {
 			insert(target, details, anchor);
-			details.open = ctx.open;
+			details.open = /*open*/ ctx[0];
 		},
-		p(changed, ctx) {
-			if (changed.open) {
-				details.open = ctx.open;
+		p(ctx, [dirty]) {
+			if (dirty & /*open*/ 1) {
+				details.open = /*open*/ ctx[0];
 			}
 		},
 		i: noop,
@@ -46,14 +46,14 @@ function instance($$self, $$props, $$invalidate) {
 
 	function details_toggle_handler() {
 		open = this.open;
-		$$invalidate("open", open);
+		$$invalidate(0, open);
 	}
 
 	$$self.$set = $$props => {
-		if ("open" in $$props) $$invalidate("open", open = $$props.open);
+		if ("open" in $$props) $$invalidate(0, open = $$props.open);
 	};
 
-	return { open, details_toggle_handler };
+	return [open, details_toggle_handler];
 }
 
 class Component extends SvelteComponent {

test/js/samples/bind-width-height/expected.js

@@ -19,11 +19,11 @@ function create_fragment(ctx) {
 		c() {
 			div = element("div");
 			div.textContent = "some content";
-			add_render_callback(() => ctx.div_elementresize_handler.call(div));
+			add_render_callback(() => /*div_elementresize_handler*/ ctx[2].call(div));
 		},
 		m(target, anchor) {
 			insert(target, div, anchor);
-			div_resize_listener = add_resize_listener(div, ctx.div_elementresize_handler.bind(div));
+			div_resize_listener = add_resize_listener(div, /*div_elementresize_handler*/ ctx[2].bind(div));
 		},
 		p: noop,
 		i: noop,
@@ -42,22 +42,22 @@ function instance($$self, $$props, $$invalidate) {
 	function div_elementresize_handler() {
 		w = this.offsetWidth;
 		h = this.offsetHeight;
-		$$invalidate("w", w);
-		$$invalidate("h", h);
+		$$invalidate(0, w);
+		$$invalidate(1, h);
 	}
 
 	$$self.$set = $$props => {
-		if ("w" in $$props) $$invalidate("w", w = $$props.w);
-		if ("h" in $$props) $$invalidate("h", h = $$props.h);
+		if ("w" in $$props) $$invalidate(0, w = $$props.w);
+		if ("h" in $$props) $$invalidate(1, h = $$props.h);
 	};
 
-	return { w, h, div_elementresize_handler };
+	return [w, h, div_elementresize_handler];
 }
 
 class Component extends SvelteComponent {
 	constructor(options) {
 		super();
-		init(this, options, instance, create_fragment, safe_not_equal, { w: 0, h: 0 });
+		init(this, options, instance, create_fragment, safe_not_equal, { w: 0, h: 1 });
 	}
 }
 

test/js/samples/bindings-readonly-order/expected.js

@@ -28,8 +28,8 @@ function create_fragment(ctx) {
 			attr(input1, "type", "file");
 
 			dispose = [
-				listen(input0, "change", ctx.input0_change_handler),
-				listen(input1, "change", ctx.input1_change_handler)
+				listen(input0, "change", /*input0_change_handler*/ ctx[1]),
+				listen(input1, "change", /*input1_change_handler*/ ctx[2])
 			];
 		},
 		m(target, anchor) {
@@ -54,23 +54,19 @@ function instance($$self, $$props, $$invalidate) {
 
 	function input0_change_handler() {
 		files = this.files;
-		$$invalidate("files", files);
+		$$invalidate(0, files);
 	}
 
 	function input1_change_handler() {
 		files = this.files;
-		$$invalidate("files", files);
+		$$invalidate(0, files);
 	}
 
 	$$self.$set = $$props => {
-		if ("files" in $$props) $$invalidate("files", files = $$props.files);
+		if ("files" in $$props) $$invalidate(0, files = $$props.files);
 	};
 
-	return {
-		files,
-		input0_change_handler,
-		input1_change_handler
-	};
+	return [files, input0_change_handler, input1_change_handler];
 }
 
 class Component extends SvelteComponent {

test/js/samples/capture-inject-dev-only/expected.js

@@ -25,23 +25,23 @@ function create_fragment(ctx) {
 	return {
 		c() {
 			p = element("p");
-			t0 = text(ctx.foo);
+			t0 = text(/*foo*/ ctx[0]);
 			t1 = space();
 			input = element("input");
-			dispose = listen(input, "input", ctx.input_input_handler);
+			dispose = listen(input, "input", /*input_input_handler*/ ctx[1]);
 		},
 		m(target, anchor) {
 			insert(target, p, anchor);
 			append(p, t0);
 			insert(target, t1, anchor);
 			insert(target, input, anchor);
-			set_input_value(input, ctx.foo);
+			set_input_value(input, /*foo*/ ctx[0]);
 		},
-		p(changed, ctx) {
-			if (changed.foo) set_data(t0, ctx.foo);
+		p(ctx, [dirty]) {
+			if (dirty & /*foo*/ 1) set_data(t0, /*foo*/ ctx[0]);
 
-			if (changed.foo && input.value !== ctx.foo) {
-				set_input_value(input, ctx.foo);
+			if (dirty & /*foo*/ 1 && input.value !== /*foo*/ ctx[0]) {
+				set_input_value(input, /*foo*/ ctx[0]);
 			}
 		},
 		i: noop,
@@ -60,10 +60,10 @@ function instance($$self, $$props, $$invalidate) {
 
 	function input_input_handler() {
 		foo = this.value;
-		$$invalidate("foo", foo);
+		$$invalidate(0, foo);
 	}
 
-	return { foo, input_input_handler };
+	return [foo, input_input_handler];
 }
 
 class Component extends SvelteComponent {

test/js/samples/collapses-text-around-comments/expected.js

@@ -27,15 +27,15 @@ function create_fragment(ctx) {
 	return {
 		c() {
 			p = element("p");
-			t = text(ctx.foo);
+			t = text(/*foo*/ ctx[0]);
 			attr(p, "class", "svelte-1a7i8ec");
 		},
 		m(target, anchor) {
 			insert(target, p, anchor);
 			append(p, t);
 		},
-		p(changed, ctx) {
-			if (changed.foo) set_data(t, ctx.foo);
+		p(ctx, [dirty]) {
+			if (dirty & /*foo*/ 1) set_data(t, /*foo*/ ctx[0]);
 		},
 		i: noop,
 		o: noop,
@@ -49,10 +49,10 @@ function instance($$self, $$props, $$invalidate) {
 	let { foo = 42 } = $$props;
 
 	$$self.$set = $$props => {
-		if ("foo" in $$props) $$invalidate("foo", foo = $$props.foo);
+		if ("foo" in $$props) $$invalidate(0, foo = $$props.foo);
 	};
 
-	return { foo };
+	return [foo];
 }
 
 class Component extends SvelteComponent {

test/js/samples/component-static-array/expected.js

@@ -13,7 +13,7 @@ import {
 
 function create_fragment(ctx) {
 	let current;
-	const nested = new ctx.Nested({ props: { foo: [1, 2, 3] } });
+	const nested = new /*Nested*/ ctx[0]({ props: { foo: [1, 2, 3] } });
 
 	return {
 		c() {
@@ -41,7 +41,7 @@ function create_fragment(ctx) {
 
 function instance($$self) {
 	const Nested = window.Nested;
-	return { Nested };
+	return [Nested];
 }
 
 class Component extends SvelteComponent {

test/js/samples/component-static-immutable/expected.js

@@ -13,7 +13,7 @@ import {
 
 function create_fragment(ctx) {
 	let current;
-	const nested = new ctx.Nested({ props: { foo: "bar" } });
+	const nested = new /*Nested*/ ctx[0]({ props: { foo: "bar" } });
 
 	return {
 		c() {
@@ -41,7 +41,7 @@ function create_fragment(ctx) {
 
 function instance($$self) {
 	const Nested = window.Nested;
-	return { Nested };
+	return [Nested];
 }
 
 class Component extends SvelteComponent {

test/js/samples/component-static-immutable2/expected.js

@@ -13,7 +13,7 @@ import {
 
 function create_fragment(ctx) {
 	let current;
-	const nested = new ctx.Nested({ props: { foo: "bar" } });
+	const nested = new /*Nested*/ ctx[0]({ props: { foo: "bar" } });
 
 	return {
 		c() {
@@ -41,7 +41,7 @@ function create_fragment(ctx) {
 
 function instance($$self) {
 	const Nested = window.Nested;
-	return { Nested };
+	return [Nested];
 }
 
 class Component extends SvelteComponent {

test/js/samples/component-static-var/expected.js

@@ -26,7 +26,7 @@ function create_fragment(ctx) {
 	let current;
 	let dispose;
 	const foo = new Foo({ props: { x: y } });
-	const bar = new Bar({ props: { x: ctx.z } });
+	const bar = new Bar({ props: { x: /*z*/ ctx[0] } });
 
 	return {
 		c() {
@@ -35,7 +35,7 @@ function create_fragment(ctx) {
 			create_component(bar.$$.fragment);
 			t1 = space();
 			input = element("input");
-			dispose = listen(input, "input", ctx.input_input_handler);
+			dispose = listen(input, "input", /*input_input_handler*/ ctx[1]);
 		},
 		m(target, anchor) {
 			mount_component(foo, target, anchor);
@@ -43,16 +43,16 @@ function create_fragment(ctx) {
 			mount_component(bar, target, anchor);
 			insert(target, t1, anchor);
 			insert(target, input, anchor);
-			set_input_value(input, ctx.z);
+			set_input_value(input, /*z*/ ctx[0]);
 			current = true;
 		},
-		p(changed, ctx) {
+		p(ctx, [dirty]) {
 			const bar_changes = {};
-			if (changed.z) bar_changes.x = ctx.z;
+			if (dirty & /*z*/ 1) bar_changes.x = /*z*/ ctx[0];
 			bar.$set(bar_changes);
 
-			if (changed.z && input.value !== ctx.z) {
-				set_input_value(input, ctx.z);
+			if (dirty & /*z*/ 1 && input.value !== /*z*/ ctx[0]) {
+				set_input_value(input, /*z*/ ctx[0]);
 			}
 		},
 		i(local) {
@@ -84,10 +84,10 @@ function instance($$self, $$props, $$invalidate) {
 
 	function input_input_handler() {
 		z = this.value;
-		$$invalidate("z", z);
+		$$invalidate(0, z);
 	}
 
-	return { z, input_input_handler };
+	return [z, input_input_handler];
 }
 
 class Component extends SvelteComponent {

test/js/samples/component-static/expected.js

@@ -13,7 +13,7 @@ import {
 
 function create_fragment(ctx) {
 	let current;
-	const nested = new ctx.Nested({ props: { foo: "bar" } });
+	const nested = new /*Nested*/ ctx[0]({ props: { foo: "bar" } });
 
 	return {
 		c() {
@@ -41,7 +41,7 @@ function create_fragment(ctx) {
 
 function instance($$self) {
 	const Nested = window.Nested;
-	return { Nested };
+	return [Nested];
 }
 
 class Component extends SvelteComponent {

test/js/samples/component-store-access-invalidate/expected.js

@@ -22,14 +22,14 @@ function create_fragment(ctx) {
 	return {
 		c() {
 			h1 = element("h1");
-			t = text(ctx.$foo);
+			t = text(/*$foo*/ ctx[0]);
 		},
 		m(target, anchor) {
 			insert(target, h1, anchor);
 			append(h1, t);
 		},
-		p(changed, ctx) {
-			if (changed.$foo) set_data(t, ctx.$foo);
+		p(ctx, [dirty]) {
+			if (dirty & /*$foo*/ 1) set_data(t, /*$foo*/ ctx[0]);
 		},
 		i: noop,
 		o: noop,
@@ -42,8 +42,8 @@ function create_fragment(ctx) {
 function instance($$self, $$props, $$invalidate) {
 	let $foo;
 	const foo = writable(0);
-	component_subscribe($$self, foo, value => $$invalidate("$foo", $foo = value));
-	return { foo, $foo };
+	component_subscribe($$self, foo, value => $$invalidate(0, $foo = value));
+	return [$foo];
 }
 
 class Component extends SvelteComponent {

test/js/samples/component-store-file-invalidate/expected.js

@@ -11,13 +11,13 @@ import { count } from "./store.js";
 
 function instance($$self, $$props, $$invalidate) {
 	let $count;
-	component_subscribe($$self, count, $$value => $$invalidate("$count", $count = $$value));
+	component_subscribe($$self, count, $$value => $$invalidate(1, $count = $$value));
 
 	function increment() {
 		set_store_value(count, $count++, $count);
 	}
 
-	return { increment };
+	return [increment];
 }
 
 class Component extends SvelteComponent {
@@ -27,7 +27,7 @@ class Component extends SvelteComponent {
 	}
 
 	get increment() {
-		return this.$$.ctx.increment;
+		return this.$$.ctx[0];
 	}
 }
 

test/js/samples/component-store-reassign-invalidate/expected.js

@@ -27,11 +27,11 @@ function create_fragment(ctx) {
 	return {
 		c() {
 			h1 = element("h1");
-			t0 = text(ctx.$foo);
+			t0 = text(/*$foo*/ ctx[1]);
 			t1 = space();
 			button = element("button");
 			button.textContent = "reset";
-			dispose = listen(button, "click", ctx.click_handler);
+			dispose = listen(button, "click", /*click_handler*/ ctx[2]);
 		},
 		m(target, anchor) {
 			insert(target, h1, anchor);
@@ -39,8 +39,8 @@ function create_fragment(ctx) {
 			insert(target, t1, anchor);
 			insert(target, button, anchor);
 		},
-		p(changed, ctx) {
-			if (changed.$foo) set_data(t0, ctx.$foo);
+		p(ctx, [dirty]) {
+			if (dirty & /*$foo*/ 2) set_data(t0, /*$foo*/ ctx[1]);
 		},
 		i: noop,
 		o: noop,
@@ -56,13 +56,13 @@ function create_fragment(ctx) {
 function instance($$self, $$props, $$invalidate) {
 	let $foo,
 		$$unsubscribe_foo = noop,
-		$$subscribe_foo = () => ($$unsubscribe_foo(), $$unsubscribe_foo = subscribe(foo, $$value => $$invalidate("$foo", $foo = $$value)), foo);
+		$$subscribe_foo = () => ($$unsubscribe_foo(), $$unsubscribe_foo = subscribe(foo, $$value => $$invalidate(1, $foo = $$value)), foo);
 
 	$$self.$$.on_destroy.push(() => $$unsubscribe_foo());
 	let foo = writable(0);
 	$$subscribe_foo();
-	const click_handler = () => $$subscribe_foo($$invalidate("foo", foo = writable(0)));
-	return { foo, $foo, click_handler };
+	const click_handler = () => $$subscribe_foo($$invalidate(0, foo = writable(0)));
+	return [foo, $foo, click_handler];
 }
 
 class Component extends SvelteComponent {

test/js/samples/computed-collapsed-if/expected.js

@@ -13,24 +13,24 @@ function instance($$self, $$props, $$invalidate) {
 	}
 
 	$$self.$set = $$props => {
-		if ("x" in $$props) $$invalidate("x", x = $$props.x);
+		if ("x" in $$props) $$invalidate(0, x = $$props.x);
 	};
 
-	return { x, a, b };
+	return [x, a, b];
 }
 
 class Component extends SvelteComponent {
 	constructor(options) {
 		super();
-		init(this, options, instance, null, safe_not_equal, { x: 0, a: 0, b: 0 });
+		init(this, options, instance, null, safe_not_equal, { x: 0, a: 1, b: 2 });
 	}
 
 	get a() {
-		return this.$$.ctx.a;
+		return this.$$.ctx[1];
 	}
 
 	get b() {
-		return this.$$.ctx.b;
+		return this.$$.ctx[2];
 	}
 }
 

test/js/samples/data-attribute/expected.js

@@ -22,16 +22,16 @@ function create_fragment(ctx) {
 			t = space();
 			div1 = element("div");
 			attr(div0, "data-foo", "bar");
-			attr(div1, "data-foo", ctx.bar);
+			attr(div1, "data-foo", /*bar*/ ctx[0]);
 		},
 		m(target, anchor) {
 			insert(target, div0, anchor);
 			insert(target, t, anchor);
 			insert(target, div1, anchor);
 		},
-		p(changed, ctx) {
-			if (changed.bar) {
-				attr(div1, "data-foo", ctx.bar);
+		p(ctx, [dirty]) {
+			if (dirty & /*bar*/ 1) {
+				attr(div1, "data-foo", /*bar*/ ctx[0]);
 			}
 		},
 		i: noop,
@@ -48,10 +48,10 @@ function instance($$self, $$props, $$invalidate) {
 	let { bar } = $$props;
 
 	$$self.$set = $$props => {
-		if ("bar" in $$props) $$invalidate("bar", bar = $$props.bar);
+		if ("bar" in $$props) $$invalidate(0, bar = $$props.bar);
 	};
 
-	return { bar };
+	return [bar];
 }
 
 class Component extends SvelteComponent {

test/js/samples/debug-empty/expected.js

@@ -28,7 +28,7 @@ function create_fragment(ctx) {
 		c: function create() {
 			h1 = element("h1");
 			t0 = text("Hello ");
-			t1 = text(ctx.name);
+			t1 = text(/*name*/ ctx[0]);
 			t2 = text("!");
 			t3 = space();
 			debugger;
@@ -44,8 +44,8 @@ function create_fragment(ctx) {
 			append_dev(h1, t2);
 			insert_dev(target, t3, anchor);
 		},
-		p: function update(changed, ctx) {
-			if (changed.name) set_data_dev(t1, ctx.name);
+		p: function update(ctx, [dirty]) {
+			if (dirty & /*name*/ 1) set_data_dev(t1, /*name*/ ctx[0]);
 			debugger;
 		},
 		i: noop,
@@ -76,7 +76,7 @@ function instance($$self, $$props, $$invalidate) {
 	});
 
 	$$self.$set = $$props => {
-		if ("name" in $$props) $$invalidate("name", name = $$props.name);
+		if ("name" in $$props) $$invalidate(0, name = $$props.name);
 	};
 
 	$$self.$capture_state = () => {
@@ -84,10 +84,10 @@ function instance($$self, $$props, $$invalidate) {
 	};
 
 	$$self.$inject_state = $$props => {
-		if ("name" in $$props) $$invalidate("name", name = $$props.name);
+		if ("name" in $$props) $$invalidate(0, name = $$props.name);
 	};
 
-	return { name };
+	return [name];
 }
 
 class Component extends SvelteComponentDev {
@@ -105,7 +105,7 @@ class Component extends SvelteComponentDev {
 		const { ctx } = this.$$;
 		const props = options.props || ({});
 
-		if (ctx.name === undefined && !("name" in props)) {
+		if (/*name*/ ctx[0] === undefined && !("name" in props)) {
 			console.warn("<Component> was created without expected prop 'name'");
 		}
 	}

test/js/samples/debug-foo-bar-baz-things/expected.js

@@ -19,15 +19,15 @@ import {
 const file = undefined;
 
 function get_each_context(ctx, list, i) {
-	const child_ctx = Object.create(ctx);
-	child_ctx.thing = list[i];
+	const child_ctx = ctx.slice();
+	child_ctx[4] = list[i];
 	return child_ctx;
 }
 
 // (8:0) {#each things as thing}
 function create_each_block(ctx) {
 	let span;
-	let t0_value = ctx.thing.name + "";
+	let t0_value = /*thing*/ ctx[4].name + "";
 	let t0;
 	let t1;
 
@@ -38,7 +38,10 @@ function create_each_block(ctx) {
 			t1 = space();
 
 			{
-				const { foo, bar, baz, thing } = ctx;
+				const foo = /*foo*/ ctx[1];
+				const bar = /*bar*/ ctx[2];
+				const baz = /*baz*/ ctx[3];
+				const thing = /*thing*/ ctx[4];
 				console.log({ foo, bar, baz, thing });
 				debugger;
 			}
@@ -50,11 +53,14 @@ function create_each_block(ctx) {
 			append_dev(span, t0);
 			insert_dev(target, t1, anchor);
 		},
-		p: function update(changed, ctx) {
-			if (changed.things && t0_value !== (t0_value = ctx.thing.name + "")) set_data_dev(t0, t0_value);
-
-			if (changed.foo || changed.bar || changed.baz || changed.things) {
-				const { foo, bar, baz, thing } = ctx;
+		p: function update(ctx, dirty) {
+			if (dirty & /*things*/ 1 && t0_value !== (t0_value = /*thing*/ ctx[4].name + "")) set_data_dev(t0, t0_value);
+
+			if (dirty & /*foo, bar, baz, things*/ 15) {
+				const foo = /*foo*/ ctx[1];
+				const bar = /*bar*/ ctx[2];
+				const baz = /*baz*/ ctx[3];
+				const thing = /*thing*/ ctx[4];
 				console.log({ foo, bar, baz, thing });
 				debugger;
 			}
@@ -81,7 +87,7 @@ function create_fragment(ctx) {
 	let p;
 	let t1;
 	let t2;
-	let each_value = ctx.things;
+	let each_value = /*things*/ ctx[0];
 	let each_blocks = [];
 
 	for (let i = 0; i < each_value.length; i += 1) {
@@ -97,7 +103,7 @@ function create_fragment(ctx) {
 			t0 = space();
 			p = element("p");
 			t1 = text("foo: ");
-			t2 = text(ctx.foo);
+			t2 = text(/*foo*/ ctx[1]);
 			add_location(p, file, 12, 0, 182);
 		},
 		l: function claim(nodes) {
@@ -113,16 +119,16 @@ function create_fragment(ctx) {
 			append_dev(p, t1);
 			append_dev(p, t2);
 		},
-		p: function update(changed, ctx) {
-			if (changed.things) {
-				each_value = ctx.things;
+		p: function update(ctx, [dirty]) {
+			if (dirty & /*things*/ 1) {
+				each_value = /*things*/ ctx[0];
 				let i;
 
 				for (i = 0; i < each_value.length; i += 1) {
 					const child_ctx = get_each_context(ctx, each_value, i);
 
 					if (each_blocks[i]) {
-						each_blocks[i].p(changed, child_ctx);
+						each_blocks[i].p(child_ctx, dirty);
 					} else {
 						each_blocks[i] = create_each_block(child_ctx);
 						each_blocks[i].c();
@@ -137,7 +143,7 @@ function create_fragment(ctx) {
 				each_blocks.length = each_value.length;
 			}
 
-			if (changed.foo) set_data_dev(t2, ctx.foo);
+			if (dirty & /*foo*/ 2) set_data_dev(t2, /*foo*/ ctx[1]);
 		},
 		i: noop,
 		o: noop,
@@ -171,10 +177,10 @@ function instance($$self, $$props, $$invalidate) {
 	});
 
 	$$self.$set = $$props => {
-		if ("things" in $$props) $$invalidate("things", things = $$props.things);
-		if ("foo" in $$props) $$invalidate("foo", foo = $$props.foo);
-		if ("bar" in $$props) $$invalidate("bar", bar = $$props.bar);
-		if ("baz" in $$props) $$invalidate("baz", baz = $$props.baz);
+		if ("things" in $$props) $$invalidate(0, things = $$props.things);
+		if ("foo" in $$props) $$invalidate(1, foo = $$props.foo);
+		if ("bar" in $$props) $$invalidate(2, bar = $$props.bar);
+		if ("baz" in $$props) $$invalidate(3, baz = $$props.baz);
 	};
 
 	$$self.$capture_state = () => {
@@ -182,19 +188,19 @@ function instance($$self, $$props, $$invalidate) {
 	};
 
 	$$self.$inject_state = $$props => {
-		if ("things" in $$props) $$invalidate("things", things = $$props.things);
-		if ("foo" in $$props) $$invalidate("foo", foo = $$props.foo);
-		if ("bar" in $$props) $$invalidate("bar", bar = $$props.bar);
-		if ("baz" in $$props) $$invalidate("baz", baz = $$props.baz);
+		if ("things" in $$props) $$invalidate(0, things = $$props.things);
+		if ("foo" in $$props) $$invalidate(1, foo = $$props.foo);
+		if ("bar" in $$props) $$invalidate(2, bar = $$props.bar);
+		if ("baz" in $$props) $$invalidate(3, baz = $$props.baz);
 	};
 
-	return { things, foo, bar, baz };
+	return [things, foo, bar, baz];
 }
 
 class Component extends SvelteComponentDev {
 	constructor(options) {
 		super(options);
-		init(this, options, instance, create_fragment, safe_not_equal, { things: 0, foo: 0, bar: 0, baz: 0 });
+		init(this, options, instance, create_fragment, safe_not_equal, { things: 0, foo: 1, bar: 2, baz: 3 });
 
 		dispatch_dev("SvelteRegisterComponent", {
 			component: this,
@@ -206,19 +212,19 @@ class Component extends SvelteComponentDev {
 		const { ctx } = this.$$;
 		const props = options.props || ({});
 
-		if (ctx.things === undefined && !("things" in props)) {
+		if (/*things*/ ctx[0] === undefined && !("things" in props)) {
 			console.warn("<Component> was created without expected prop 'things'");
 		}
 
-		if (ctx.foo === undefined && !("foo" in props)) {
+		if (/*foo*/ ctx[1] === undefined && !("foo" in props)) {
 			console.warn("<Component> was created without expected prop 'foo'");
 		}
 
-		if (ctx.bar === undefined && !("bar" in props)) {
+		if (/*bar*/ ctx[2] === undefined && !("bar" in props)) {
 			console.warn("<Component> was created without expected prop 'bar'");
 		}
 
-		if (ctx.baz === undefined && !("baz" in props)) {
+		if (/*baz*/ ctx[3] === undefined && !("baz" in props)) {
 			console.warn("<Component> was created without expected prop 'baz'");
 		}
 	}

test/js/samples/debug-foo/expected.js

@@ -19,15 +19,15 @@ import {
 const file = undefined;
 
 function get_each_context(ctx, list, i) {
-	const child_ctx = Object.create(ctx);
-	child_ctx.thing = list[i];
+	const child_ctx = ctx.slice();
+	child_ctx[2] = list[i];
 	return child_ctx;
 }
 
 // (6:0) {#each things as thing}
 function create_each_block(ctx) {
 	let span;
-	let t0_value = ctx.thing.name + "";
+	let t0_value = /*thing*/ ctx[2].name + "";
 	let t0;
 	let t1;
 
@@ -38,7 +38,7 @@ function create_each_block(ctx) {
 			t1 = space();
 
 			{
-				const { foo } = ctx;
+				const foo = /*foo*/ ctx[1];
 				console.log({ foo });
 				debugger;
 			}
@@ -50,11 +50,11 @@ function create_each_block(ctx) {
 			append_dev(span, t0);
 			insert_dev(target, t1, anchor);
 		},
-		p: function update(changed, ctx) {
-			if (changed.things && t0_value !== (t0_value = ctx.thing.name + "")) set_data_dev(t0, t0_value);
+		p: function update(ctx, dirty) {
+			if (dirty & /*things*/ 1 && t0_value !== (t0_value = /*thing*/ ctx[2].name + "")) set_data_dev(t0, t0_value);
 
-			if (changed.foo) {
-				const { foo } = ctx;
+			if (dirty & /*foo*/ 2) {
+				const foo = /*foo*/ ctx[1];
 				console.log({ foo });
 				debugger;
 			}
@@ -81,7 +81,7 @@ function create_fragment(ctx) {
 	let p;
 	let t1;
 	let t2;
-	let each_value = ctx.things;
+	let each_value = /*things*/ ctx[0];
 	let each_blocks = [];
 
 	for (let i = 0; i < each_value.length; i += 1) {
@@ -97,7 +97,7 @@ function create_fragment(ctx) {
 			t0 = space();
 			p = element("p");
 			t1 = text("foo: ");
-			t2 = text(ctx.foo);
+			t2 = text(/*foo*/ ctx[1]);
 			add_location(p, file, 10, 0, 131);
 		},
 		l: function claim(nodes) {
@@ -113,16 +113,16 @@ function create_fragment(ctx) {
 			append_dev(p, t1);
 			append_dev(p, t2);
 		},
-		p: function update(changed, ctx) {
-			if (changed.things) {
-				each_value = ctx.things;
+		p: function update(ctx, [dirty]) {
+			if (dirty & /*things*/ 1) {
+				each_value = /*things*/ ctx[0];
 				let i;
 
 				for (i = 0; i < each_value.length; i += 1) {
 					const child_ctx = get_each_context(ctx, each_value, i);
 
 					if (each_blocks[i]) {
-						each_blocks[i].p(changed, child_ctx);
+						each_blocks[i].p(child_ctx, dirty);
 					} else {
 						each_blocks[i] = create_each_block(child_ctx);
 						each_blocks[i].c();
@@ -137,7 +137,7 @@ function create_fragment(ctx) {
 				each_blocks.length = each_value.length;
 			}
 
-			if (changed.foo) set_data_dev(t2, ctx.foo);
+			if (dirty & /*foo*/ 2) set_data_dev(t2, /*foo*/ ctx[1]);
 		},
 		i: noop,
 		o: noop,
@@ -169,8 +169,8 @@ function instance($$self, $$props, $$invalidate) {
 	});
 
 	$$self.$set = $$props => {
-		if ("things" in $$props) $$invalidate("things", things = $$props.things);
-		if ("foo" in $$props) $$invalidate("foo", foo = $$props.foo);
+		if ("things" in $$props) $$invalidate(0, things = $$props.things);
+		if ("foo" in $$props) $$invalidate(1, foo = $$props.foo);
 	};
 
 	$$self.$capture_state = () => {
@@ -178,17 +178,17 @@ function instance($$self, $$props, $$invalidate) {
 	};
 
 	$$self.$inject_state = $$props => {
-		if ("things" in $$props) $$invalidate("things", things = $$props.things);
-		if ("foo" in $$props) $$invalidate("foo", foo = $$props.foo);
+		if ("things" in $$props) $$invalidate(0, things = $$props.things);
+		if ("foo" in $$props) $$invalidate(1, foo = $$props.foo);
 	};
 
-	return { things, foo };
+	return [things, foo];
 }
 
 class Component extends SvelteComponentDev {
 	constructor(options) {
 		super(options);
-		init(this, options, instance, create_fragment, safe_not_equal, { things: 0, foo: 0 });
+		init(this, options, instance, create_fragment, safe_not_equal, { things: 0, foo: 1 });
 
 		dispatch_dev("SvelteRegisterComponent", {
 			component: this,
@@ -200,11 +200,11 @@ class Component extends SvelteComponentDev {
 		const { ctx } = this.$$;
 		const props = options.props || ({});
 
-		if (ctx.things === undefined && !("things" in props)) {
+		if (/*things*/ ctx[0] === undefined && !("things" in props)) {
 			console.warn("<Component> was created without expected prop 'things'");
 		}
 
-		if (ctx.foo === undefined && !("foo" in props)) {
+		if (/*foo*/ ctx[1] === undefined && !("foo" in props)) {
 			console.warn("<Component> was created without expected prop 'foo'");
 		}
 	}

test/js/samples/debug-hoisted/expected.js

@@ -13,7 +13,8 @@ function create_fragment(ctx) {
 	const block = {
 		c: function create() {
 			{
-				const { obj } = ctx;
+				const obj = /*obj*/ ctx[0];
+				const kobzol = /*kobzol*/ ctx[1];
 				console.log({ obj, kobzol });
 				debugger;
 			}
@@ -22,9 +23,10 @@ function create_fragment(ctx) {
 			throw new Error("options.hydrate only works if the component was compiled with the `hydratable: true` option");
 		},
 		m: noop,
-		p: function update(changed, ctx) {
-			if (changed.obj || changed.kobzol) {
-				const { obj } = ctx;
+		p: function update(ctx, [dirty]) {
+			if (dirty & /*obj, kobzol*/ 3) {
+				const obj = /*obj*/ ctx[0];
+				const kobzol = /*kobzol*/ ctx[1];
 				console.log({ obj, kobzol });
 				debugger;
 			}
@@ -45,21 +47,20 @@ function create_fragment(ctx) {
 	return block;
 }
 
-let kobzol = 5;
-
 function instance($$self) {
 	let obj = { x: 5 };
+	let kobzol = 5;
 
 	$$self.$capture_state = () => {
 		return {};
 	};
 
 	$$self.$inject_state = $$props => {
-		if ("obj" in $$props) $$invalidate("obj", obj = $$props.obj);
-		if ("kobzol" in $$props) $$invalidate("kobzol", kobzol = $$props.kobzol);
+		if ("obj" in $$props) $$invalidate(0, obj = $$props.obj);
+		if ("kobzol" in $$props) $$invalidate(1, kobzol = $$props.kobzol);
 	};
 
-	return { obj };
+	return [obj, kobzol];
 }
 
 class Component extends SvelteComponentDev {

test/js/samples/debug-no-dependencies/expected.js

@@ -16,22 +16,22 @@ import {
 const file = undefined;
 
 function get_each_context(ctx, list, i) {
-	const child_ctx = Object.create(ctx);
-	child_ctx.thing = list[i];
-	child_ctx.index = i;
+	const child_ctx = ctx.slice();
+	child_ctx[0] = list[i];
+	child_ctx[2] = i;
 	return child_ctx;
 }
 
 // (4:0) {#each things as thing, index}
 function create_each_block(ctx) {
 	let t0;
-	let t1_value = ctx.thing + "";
+	let t1_value = /*thing*/ ctx[0] + "";
 	let t1;
 
 	const block = {
 		c: function create() {
 			{
-				const { index } = ctx;
+				const index = /*index*/ ctx[2];
 				console.log({ index });
 				debugger;
 			}
@@ -88,8 +88,8 @@ function create_fragment(ctx) {
 
 			insert_dev(target, each_1_anchor, anchor);
 		},
-		p: function update(changed, ctx) {
-			if (changed.things) {
+		p: function update(ctx, [dirty]) {
+			if (dirty & /*things*/ 0) {
 				each_value = things;
 				let i;
 
@@ -97,7 +97,7 @@ function create_fragment(ctx) {
 					const child_ctx = get_each_context(ctx, each_value, i);
 
 					if (each_blocks[i]) {
-						each_blocks[i].p(changed, child_ctx);
+						each_blocks[i].p(child_ctx, dirty);
 					} else {
 						each_blocks[i] = create_each_block(child_ctx);
 						each_blocks[i].c();

test/js/samples/deconflict-builtins/expected.js

@@ -15,15 +15,15 @@ import {
 } from "svelte/internal";
 
 function get_each_context(ctx, list, i) {
-	const child_ctx = Object.create(ctx);
-	child_ctx.node = list[i];
+	const child_ctx = ctx.slice();
+	child_ctx[1] = list[i];
 	return child_ctx;
 }
 
 // (5:0) {#each createElement as node}
 function create_each_block(ctx) {
 	let span;
-	let t_value = ctx.node + "";
+	let t_value = /*node*/ ctx[1] + "";
 	let t;
 
 	return {
@@ -35,8 +35,8 @@ function create_each_block(ctx) {
 			insert(target, span, anchor);
 			append(span, t);
 		},
-		p(changed, ctx) {
-			if (changed.createElement && t_value !== (t_value = ctx.node + "")) set_data(t, t_value);
+		p(ctx, dirty) {
+			if (dirty & /*createElement*/ 1 && t_value !== (t_value = /*node*/ ctx[1] + "")) set_data(t, t_value);
 		},
 		d(detaching) {
 			if (detaching) detach(span);
@@ -46,7 +46,7 @@ function create_each_block(ctx) {
 
 function create_fragment(ctx) {
 	let each_1_anchor;
-	let each_value = ctx.createElement;
+	let each_value = /*createElement*/ ctx[0];
 	let each_blocks = [];
 
 	for (let i = 0; i < each_value.length; i += 1) {
@@ -68,16 +68,16 @@ function create_fragment(ctx) {
 
 			insert(target, each_1_anchor, anchor);
 		},
-		p(changed, ctx) {
-			if (changed.createElement) {
-				each_value = ctx.createElement;
+		p(ctx, [dirty]) {
+			if (dirty & /*createElement*/ 1) {
+				each_value = /*createElement*/ ctx[0];
 				let i;
 
 				for (i = 0; i < each_value.length; i += 1) {
 					const child_ctx = get_each_context(ctx, each_value, i);
 
 					if (each_blocks[i]) {
-						each_blocks[i].p(changed, child_ctx);
+						each_blocks[i].p(child_ctx, dirty);
 					} else {
 						each_blocks[i] = create_each_block(child_ctx);
 						each_blocks[i].c();
@@ -105,10 +105,10 @@ function instance($$self, $$props, $$invalidate) {
 	let { createElement } = $$props;
 
 	$$self.$set = $$props => {
-		if ("createElement" in $$props) $$invalidate("createElement", createElement = $$props.createElement);
+		if ("createElement" in $$props) $$invalidate(0, createElement = $$props.createElement);
 	};
 
-	return { createElement };
+	return [createElement];
 }
 
 class Component extends SvelteComponent {

test/js/samples/deconflict-globals/expected.js

@@ -11,10 +11,10 @@ function instance($$self, $$props, $$invalidate) {
 	});
 
 	$$self.$set = $$props => {
-		if ("foo" in $$props) $$invalidate("foo", foo = $$props.foo);
+		if ("foo" in $$props) $$invalidate(0, foo = $$props.foo);
 	};
 
-	return { foo };
+	return [foo];
 }
 
 class Component extends SvelteComponent {

test/js/samples/dev-warning-missing-data-computed/expected.js

@@ -19,7 +19,7 @@ const file = undefined;
 
 function create_fragment(ctx) {
 	let p;
-	let t0_value = Math.max(0, ctx.foo) + "";
+	let t0_value = Math.max(0, /*foo*/ ctx[0]) + "";
 	let t0;
 	let t1;
 	let t2;
@@ -29,7 +29,7 @@ function create_fragment(ctx) {
 			p = element("p");
 			t0 = text(t0_value);
 			t1 = space();
-			t2 = text(ctx.bar);
+			t2 = text(/*bar*/ ctx[1]);
 			add_location(p, file, 7, 0, 67);
 		},
 		l: function claim(nodes) {
@@ -41,9 +41,9 @@ function create_fragment(ctx) {
 			append_dev(p, t1);
 			append_dev(p, t2);
 		},
-		p: function update(changed, ctx) {
-			if (changed.foo && t0_value !== (t0_value = Math.max(0, ctx.foo) + "")) set_data_dev(t0, t0_value);
-			if (changed.bar) set_data_dev(t2, ctx.bar);
+		p: function update(ctx, [dirty]) {
+			if (dirty & /*foo*/ 1 && t0_value !== (t0_value = Math.max(0, /*foo*/ ctx[0]) + "")) set_data_dev(t0, t0_value);
+			if (dirty & /*bar*/ 2) set_data_dev(t2, /*bar*/ ctx[1]);
 		},
 		i: noop,
 		o: noop,
@@ -73,7 +73,7 @@ function instance($$self, $$props, $$invalidate) {
 	});
 
 	$$self.$set = $$props => {
-		if ("foo" in $$props) $$invalidate("foo", foo = $$props.foo);
+		if ("foo" in $$props) $$invalidate(0, foo = $$props.foo);
 	};
 
 	$$self.$capture_state = () => {
@@ -81,17 +81,17 @@ function instance($$self, $$props, $$invalidate) {
 	};
 
 	$$self.$inject_state = $$props => {
-		if ("foo" in $$props) $$invalidate("foo", foo = $$props.foo);
-		if ("bar" in $$props) $$invalidate("bar", bar = $$props.bar);
+		if ("foo" in $$props) $$invalidate(0, foo = $$props.foo);
+		if ("bar" in $$props) $$invalidate(1, bar = $$props.bar);
 	};
 
-	$$self.$$.update = (changed = { foo: 1 }) => {
-		if (changed.foo) {
-			$: $$invalidate("bar", bar = foo * 2);
+	$$self.$$.update = () => {
+		if ($$self.$$.dirty & /*foo*/ 1) {
+			$: $$invalidate(1, bar = foo * 2);
 		}
 	};
 
-	return { foo, bar };
+	return [foo, bar];
 }
 
 class Component extends SvelteComponentDev {
@@ -109,7 +109,7 @@ class Component extends SvelteComponentDev {
 		const { ctx } = this.$$;
 		const props = options.props || ({});
 
-		if (ctx.foo === undefined && !("foo" in props)) {
+		if (/*foo*/ ctx[0] === undefined && !("foo" in props)) {
 			console.warn("<Component> was created without expected prop 'foo'");
 		}
 	}

test/js/samples/each-block-array-literal/expected.js

@@ -15,15 +15,15 @@ import {
 } from "svelte/internal";
 
 function get_each_context(ctx, list, i) {
-	const child_ctx = Object.create(ctx);
-	child_ctx.num = list[i];
+	const child_ctx = ctx.slice();
+	child_ctx[5] = list[i];
 	return child_ctx;
 }
 
 // (9:0) {#each [a, b, c, d, e] as num}
 function create_each_block(ctx) {
 	let span;
-	let t_value = ctx.num + "";
+	let t_value = /*num*/ ctx[5] + "";
 	let t;
 
 	return {
@@ -35,8 +35,8 @@ function create_each_block(ctx) {
 			insert(target, span, anchor);
 			append(span, t);
 		},
-		p(changed, ctx) {
-			if ((changed.a || changed.b || changed.c || changed.d || changed.e) && t_value !== (t_value = ctx.num + "")) set_data(t, t_value);
+		p(ctx, dirty) {
+			if (dirty & /*a, b, c, d, e*/ 31 && t_value !== (t_value = /*num*/ ctx[5] + "")) set_data(t, t_value);
 		},
 		d(detaching) {
 			if (detaching) detach(span);
@@ -46,7 +46,7 @@ function create_each_block(ctx) {
 
 function create_fragment(ctx) {
 	let each_1_anchor;
-	let each_value = [ctx.a, ctx.b, ctx.c, ctx.d, ctx.e];
+	let each_value = [/*a*/ ctx[0], /*b*/ ctx[1], /*c*/ ctx[2], /*d*/ ctx[3], /*e*/ ctx[4]];
 	let each_blocks = [];
 
 	for (let i = 0; i < 5; i += 1) {
@@ -68,16 +68,16 @@ function create_fragment(ctx) {
 
 			insert(target, each_1_anchor, anchor);
 		},
-		p(changed, ctx) {
-			if (changed.a || changed.b || changed.c || changed.d || changed.e) {
-				each_value = [ctx.a, ctx.b, ctx.c, ctx.d, ctx.e];
+		p(ctx, [dirty]) {
+			if (dirty & /*a, b, c, d, e*/ 31) {
+				each_value = [/*a*/ ctx[0], /*b*/ ctx[1], /*c*/ ctx[2], /*d*/ ctx[3], /*e*/ ctx[4]];
 				let i;
 
 				for (i = 0; i < 5; i += 1) {
 					const child_ctx = get_each_context(ctx, each_value, i);
 
 					if (each_blocks[i]) {
-						each_blocks[i].p(changed, child_ctx);
+						each_blocks[i].p(child_ctx, dirty);
 					} else {
 						each_blocks[i] = create_each_block(child_ctx);
 						each_blocks[i].c();
@@ -107,20 +107,20 @@ function instance($$self, $$props, $$invalidate) {
 	let { e } = $$props;
 
 	$$self.$set = $$props => {
-		if ("a" in $$props) $$invalidate("a", a = $$props.a);
-		if ("b" in $$props) $$invalidate("b", b = $$props.b);
-		if ("c" in $$props) $$invalidate("c", c = $$props.c);
-		if ("d" in $$props) $$invalidate("d", d = $$props.d);
-		if ("e" in $$props) $$invalidate("e", e = $$props.e);
+		if ("a" in $$props) $$invalidate(0, a = $$props.a);
+		if ("b" in $$props) $$invalidate(1, b = $$props.b);
+		if ("c" in $$props) $$invalidate(2, c = $$props.c);
+		if ("d" in $$props) $$invalidate(3, d = $$props.d);
+		if ("e" in $$props) $$invalidate(4, e = $$props.e);
 	};
 
-	return { a, b, c, d, e };
+	return [a, b, c, d, e];
 }
 
 class Component extends SvelteComponent {
 	constructor(options) {
 		super();
-		init(this, options, instance, create_fragment, safe_not_equal, { a: 0, b: 0, c: 0, d: 0, e: 0 });
+		init(this, options, instance, create_fragment, safe_not_equal, { a: 0, b: 1, c: 2, d: 3, e: 4 });
 	}
 }
 

test/js/samples/each-block-changed-check/expected.js

@@ -17,9 +17,9 @@ import {
 } from "svelte/internal";
 
 function get_each_context(ctx, list, i) {
-	const child_ctx = Object.create(ctx);
-	child_ctx.comment = list[i];
-	child_ctx.i = i;
+	const child_ctx = ctx.slice();
+	child_ctx[4] = list[i];
+	child_ctx[6] = i;
 	return child_ctx;
 }
 
@@ -30,21 +30,21 @@ function create_each_block(ctx) {
 	let t0;
 	let t1;
 	let span;
-	let t2_value = ctx.comment.author + "";
+	let t2_value = /*comment*/ ctx[4].author + "";
 	let t2;
 	let t3;
-	let t4_value = ctx.elapsed(ctx.comment.time, ctx.time) + "";
+	let t4_value = /*elapsed*/ ctx[1](/*comment*/ ctx[4].time, /*time*/ ctx[2]) + "";
 	let t4;
 	let t5;
 	let t6;
 	let html_tag;
-	let raw_value = ctx.comment.html + "";
+	let raw_value = /*comment*/ ctx[4].html + "";
 
 	return {
 		c() {
 			div = element("div");
 			strong = element("strong");
-			t0 = text(ctx.i);
+			t0 = text(/*i*/ ctx[6]);
 			t1 = space();
 			span = element("span");
 			t2 = text(t2_value);
@@ -69,10 +69,10 @@ function create_each_block(ctx) {
 			append(div, t6);
 			html_tag.m(div);
 		},
-		p(changed, ctx) {
-			if (changed.comments && t2_value !== (t2_value = ctx.comment.author + "")) set_data(t2, t2_value);
-			if ((changed.elapsed || changed.comments || changed.time) && t4_value !== (t4_value = ctx.elapsed(ctx.comment.time, ctx.time) + "")) set_data(t4, t4_value);
-			if (changed.comments && raw_value !== (raw_value = ctx.comment.html + "")) html_tag.p(raw_value);
+		p(ctx, dirty) {
+			if (dirty & /*comments*/ 1 && t2_value !== (t2_value = /*comment*/ ctx[4].author + "")) set_data(t2, t2_value);
+			if (dirty & /*elapsed, comments, time*/ 7 && t4_value !== (t4_value = /*elapsed*/ ctx[1](/*comment*/ ctx[4].time, /*time*/ ctx[2]) + "")) set_data(t4, t4_value);
+			if (dirty & /*comments*/ 1 && raw_value !== (raw_value = /*comment*/ ctx[4].html + "")) html_tag.p(raw_value);
 		},
 		d(detaching) {
 			if (detaching) detach(div);
@@ -84,7 +84,7 @@ function create_fragment(ctx) {
 	let t0;
 	let p;
 	let t1;
-	let each_value = ctx.comments;
+	let each_value = /*comments*/ ctx[0];
 	let each_blocks = [];
 
 	for (let i = 0; i < each_value.length; i += 1) {
@@ -99,7 +99,7 @@ function create_fragment(ctx) {
 
 			t0 = space();
 			p = element("p");
-			t1 = text(ctx.foo);
+			t1 = text(/*foo*/ ctx[3]);
 		},
 		m(target, anchor) {
 			for (let i = 0; i < each_blocks.length; i += 1) {
@@ -110,16 +110,16 @@ function create_fragment(ctx) {
 			insert(target, p, anchor);
 			append(p, t1);
 		},
-		p(changed, ctx) {
-			if (changed.comments || changed.elapsed || changed.time) {
-				each_value = ctx.comments;
+		p(ctx, [dirty]) {
+			if (dirty & /*comments, elapsed, time*/ 7) {
+				each_value = /*comments*/ ctx[0];
 				let i;
 
 				for (i = 0; i < each_value.length; i += 1) {
 					const child_ctx = get_each_context(ctx, each_value, i);
 
 					if (each_blocks[i]) {
-						each_blocks[i].p(changed, child_ctx);
+						each_blocks[i].p(child_ctx, dirty);
 					} else {
 						each_blocks[i] = create_each_block(child_ctx);
 						each_blocks[i].c();
@@ -134,7 +134,7 @@ function create_fragment(ctx) {
 				each_blocks.length = each_value.length;
 			}
 
-			if (changed.foo) set_data(t1, ctx.foo);
+			if (dirty & /*foo*/ 8) set_data(t1, /*foo*/ ctx[3]);
 		},
 		i: noop,
 		o: noop,
@@ -153,19 +153,19 @@ function instance($$self, $$props, $$invalidate) {
 	let { foo } = $$props;
 
 	$$self.$set = $$props => {
-		if ("comments" in $$props) $$invalidate("comments", comments = $$props.comments);
-		if ("elapsed" in $$props) $$invalidate("elapsed", elapsed = $$props.elapsed);
-		if ("time" in $$props) $$invalidate("time", time = $$props.time);
-		if ("foo" in $$props) $$invalidate("foo", foo = $$props.foo);
+		if ("comments" in $$props) $$invalidate(0, comments = $$props.comments);
+		if ("elapsed" in $$props) $$invalidate(1, elapsed = $$props.elapsed);
+		if ("time" in $$props) $$invalidate(2, time = $$props.time);
+		if ("foo" in $$props) $$invalidate(3, foo = $$props.foo);
 	};
 
-	return { comments, elapsed, time, foo };
+	return [comments, elapsed, time, foo];
 }
 
 class Component extends SvelteComponent {
 	constructor(options) {
 		super();
-		init(this, options, instance, create_fragment, safe_not_equal, { comments: 0, elapsed: 0, time: 0, foo: 0 });
+		init(this, options, instance, create_fragment, safe_not_equal, { comments: 0, elapsed: 1, time: 2, foo: 3 });
 	}
 }
 

test/js/samples/each-block-keyed-animated/expected.js

@@ -18,15 +18,15 @@ import {
 } from "svelte/internal";
 
 function get_each_context(ctx, list, i) {
-	const child_ctx = Object.create(ctx);
-	child_ctx.thing = list[i];
+	const child_ctx = ctx.slice();
+	child_ctx[1] = list[i];
 	return child_ctx;
 }
 
 // (19:0) {#each things as thing (thing.id)}
 function create_each_block(key_1, ctx) {
 	let div;
-	let t_value = ctx.thing.name + "";
+	let t_value = /*thing*/ ctx[1].name + "";
 	let t;
 	let rect;
 	let stop_animation = noop;
@@ -43,8 +43,8 @@ function create_each_block(key_1, ctx) {
 			insert(target, div, anchor);
 			append(div, t);
 		},
-		p(changed, ctx) {
-			if (changed.things && t_value !== (t_value = ctx.thing.name + "")) set_data(t, t_value);
+		p(ctx, dirty) {
+			if (dirty & /*things*/ 1 && t_value !== (t_value = /*thing*/ ctx[1].name + "")) set_data(t, t_value);
 		},
 		r() {
 			rect = div.getBoundingClientRect();
@@ -67,8 +67,8 @@ function create_fragment(ctx) {
 	let each_blocks = [];
 	let each_1_lookup = new Map();
 	let each_1_anchor;
-	let each_value = ctx.things;
-	const get_key = ctx => ctx.thing.id;
+	let each_value = /*things*/ ctx[0];
+	const get_key = ctx => /*thing*/ ctx[1].id;
 
 	for (let i = 0; i < each_value.length; i += 1) {
 		let child_ctx = get_each_context(ctx, each_value, i);
@@ -91,10 +91,10 @@ function create_fragment(ctx) {
 
 			insert(target, each_1_anchor, anchor);
 		},
-		p(changed, ctx) {
-			const each_value = ctx.things;
+		p(ctx, [dirty]) {
+			const each_value = /*things*/ ctx[0];
 			for (let i = 0; i < each_blocks.length; i += 1) each_blocks[i].r();
-			each_blocks = update_keyed_each(each_blocks, changed, get_key, 1, ctx, each_value, each_1_lookup, each_1_anchor.parentNode, fix_and_destroy_block, create_each_block, each_1_anchor, get_each_context);
+			each_blocks = update_keyed_each(each_blocks, dirty, get_key, 1, ctx, each_value, each_1_lookup, each_1_anchor.parentNode, fix_and_destroy_block, create_each_block, each_1_anchor, get_each_context);
 			for (let i = 0; i < each_blocks.length; i += 1) each_blocks[i].a();
 		},
 		i: noop,
@@ -127,10 +127,10 @@ function instance($$self, $$props, $$invalidate) {
 	let { things } = $$props;
 
 	$$self.$set = $$props => {
-		if ("things" in $$props) $$invalidate("things", things = $$props.things);
+		if ("things" in $$props) $$invalidate(0, things = $$props.things);
 	};
 
-	return { things };
+	return [things];
 }
 
 class Component extends SvelteComponent {

test/js/samples/each-block-keyed/expected.js

@@ -16,15 +16,15 @@ import {
 } from "svelte/internal";
 
 function get_each_context(ctx, list, i) {
-	const child_ctx = Object.create(ctx);
-	child_ctx.thing = list[i];
+	const child_ctx = ctx.slice();
+	child_ctx[1] = list[i];
 	return child_ctx;
 }
 
 // (5:0) {#each things as thing (thing.id)}
 function create_each_block(key_1, ctx) {
 	let div;
-	let t_value = ctx.thing.name + "";
+	let t_value = /*thing*/ ctx[1].name + "";
 	let t;
 
 	return {
@@ -39,8 +39,8 @@ function create_each_block(key_1, ctx) {
 			insert(target, div, anchor);
 			append(div, t);
 		},
-		p(changed, ctx) {
-			if (changed.things && t_value !== (t_value = ctx.thing.name + "")) set_data(t, t_value);
+		p(ctx, dirty) {
+			if (dirty & /*things*/ 1 && t_value !== (t_value = /*thing*/ ctx[1].name + "")) set_data(t, t_value);
 		},
 		d(detaching) {
 			if (detaching) detach(div);
@@ -52,8 +52,8 @@ function create_fragment(ctx) {
 	let each_blocks = [];
 	let each_1_lookup = new Map();
 	let each_1_anchor;
-	let each_value = ctx.things;
-	const get_key = ctx => ctx.thing.id;
+	let each_value = /*things*/ ctx[0];
+	const get_key = ctx => /*thing*/ ctx[1].id;
 
 	for (let i = 0; i < each_value.length; i += 1) {
 		let child_ctx = get_each_context(ctx, each_value, i);
@@ -76,9 +76,9 @@ function create_fragment(ctx) {
 
 			insert(target, each_1_anchor, anchor);
 		},
-		p(changed, ctx) {
-			const each_value = ctx.things;
-			each_blocks = update_keyed_each(each_blocks, changed, get_key, 1, ctx, each_value, each_1_lookup, each_1_anchor.parentNode, destroy_block, create_each_block, each_1_anchor, get_each_context);
+		p(ctx, [dirty]) {
+			const each_value = /*things*/ ctx[0];
+			each_blocks = update_keyed_each(each_blocks, dirty, get_key, 1, ctx, each_value, each_1_lookup, each_1_anchor.parentNode, destroy_block, create_each_block, each_1_anchor, get_each_context);
 		},
 		i: noop,
 		o: noop,
@@ -96,10 +96,10 @@ function instance($$self, $$props, $$invalidate) {
 	let { things } = $$props;
 
 	$$self.$set = $$props => {
-		if ("things" in $$props) $$invalidate("things", things = $$props.things);
+		if ("things" in $$props) $$invalidate(0, things = $$props.things);
 	};
 
-	return { things };
+	return [things];
 }
 
 class Component extends SvelteComponent {

test/js/samples/empty-dom/expected.js

@@ -3,7 +3,7 @@ import { SvelteComponent, init, safe_not_equal } from "svelte/internal";
 
 function instance($$self) {
 	const a = 1 + 2;
-	return {};
+	return [];
 }
 
 class Component extends SvelteComponent {

test/js/samples/event-handler-dynamic/expected.js

@@ -37,16 +37,16 @@ function create_fragment(ctx) {
 			button1.textContent = "set handler 2";
 			t3 = space();
 			p1 = element("p");
-			t4 = text(ctx.number);
+			t4 = text(/*number*/ ctx[1]);
 			t5 = space();
 			button2 = element("button");
 			button2.textContent = "click";
 
 			dispose = [
-				listen(button0, "click", ctx.updateHandler1),
-				listen(button1, "click", ctx.updateHandler2),
+				listen(button0, "click", /*updateHandler1*/ ctx[2]),
+				listen(button1, "click", /*updateHandler2*/ ctx[3]),
 				listen(button2, "click", function () {
-					ctx.clickHandler.apply(this, arguments);
+					/*clickHandler*/ ctx[0].apply(this, arguments);
 				})
 			];
 		},
@@ -61,9 +61,9 @@ function create_fragment(ctx) {
 			insert(target, t5, anchor);
 			insert(target, button2, anchor);
 		},
-		p(changed, new_ctx) {
+		p(new_ctx, [dirty]) {
 			ctx = new_ctx;
-			if (changed.number) set_data(t4, ctx.number);
+			if (dirty & /*number*/ 2) set_data(t4, /*number*/ ctx[1]);
 		},
 		i: noop,
 		o: noop,
@@ -83,19 +83,14 @@ function instance($$self, $$props, $$invalidate) {
 	let number = 0;
 
 	function updateHandler1() {
-		$$invalidate("clickHandler", clickHandler = () => $$invalidate("number", number = 1));
+		$$invalidate(0, clickHandler = () => $$invalidate(1, number = 1));
 	}
 
 	function updateHandler2() {
-		$$invalidate("clickHandler", clickHandler = () => $$invalidate("number", number = 2));
+		$$invalidate(0, clickHandler = () => $$invalidate(1, number = 2));
 	}
 
-	return {
-		clickHandler,
-		number,
-		updateHandler1,
-		updateHandler2
-	};
+	return [clickHandler, number, updateHandler1, updateHandler2];
 }
 
 class Component extends SvelteComponent {

test/js/samples/if-block-complex/expected.js

@@ -29,7 +29,7 @@ function create_if_block(ctx) {
 }
 
 function create_fragment(ctx) {
-	let show_if = ctx.item.divider && ctx.item.divider.includes(1);
+	let show_if = /*item*/ ctx[0].divider && /*item*/ ctx[0].divider.includes(1);
 	let if_block_anchor;
 	let if_block = show_if && create_if_block(ctx);
 
@@ -54,7 +54,7 @@ function create_fragment(ctx) {
 
 function instance($$self) {
 	let item = { divider: [1] };
-	return { item };
+	return [item];
 }
 
 class Component extends SvelteComponent {

test/js/samples/if-block-no-update/expected.js

@@ -48,12 +48,12 @@ function create_if_block(ctx) {
 function create_fragment(ctx) {
 	let if_block_anchor;
 
-	function select_block_type(changed, ctx) {
-		if (ctx.foo) return create_if_block;
+	function select_block_type(ctx, dirty) {
+		if (/*foo*/ ctx[0]) return create_if_block;
 		return create_else_block;
 	}
 
-	let current_block_type = select_block_type(null, ctx);
+	let current_block_type = select_block_type(ctx, -1);
 	let if_block = current_block_type(ctx);
 
 	return {
@@ -65,8 +65,8 @@ function create_fragment(ctx) {
 			if_block.m(target, anchor);
 			insert(target, if_block_anchor, anchor);
 		},
-		p(changed, ctx) {
-			if (current_block_type !== (current_block_type = select_block_type(changed, ctx))) {
+		p(ctx, [dirty]) {
+			if (current_block_type !== (current_block_type = select_block_type(ctx, dirty))) {
 				if_block.d(1);
 				if_block = current_block_type(ctx);
 
@@ -89,10 +89,10 @@ function instance($$self, $$props, $$invalidate) {
 	let { foo } = $$props;
 
 	$$self.$set = $$props => {
-		if ("foo" in $$props) $$invalidate("foo", foo = $$props.foo);
+		if ("foo" in $$props) $$invalidate(0, foo = $$props.foo);
 	};
 
-	return { foo };
+	return [foo];
 }
 
 class Component extends SvelteComponent {

test/js/samples/if-block-simple/expected.js

@@ -29,7 +29,7 @@ function create_if_block(ctx) {
 
 function create_fragment(ctx) {
 	let if_block_anchor;
-	let if_block = ctx.foo && create_if_block(ctx);
+	let if_block = /*foo*/ ctx[0] && create_if_block(ctx);
 
 	return {
 		c() {
@@ -40,8 +40,8 @@ function create_fragment(ctx) {
 			if (if_block) if_block.m(target, anchor);
 			insert(target, if_block_anchor, anchor);
 		},
-		p(changed, ctx) {
-			if (ctx.foo) {
+		p(ctx, [dirty]) {
+			if (/*foo*/ ctx[0]) {
 				if (!if_block) {
 					if_block = create_if_block(ctx);
 					if_block.c();
@@ -67,10 +67,10 @@ function instance($$self, $$props, $$invalidate) {
 	let { foo } = $$props;
 
 	$$self.$set = $$props => {
-		if ("foo" in $$props) $$invalidate("foo", foo = $$props.foo);
+		if ("foo" in $$props) $$invalidate(0, foo = $$props.foo);
 	};
 
-	return { foo };
+	return [foo];
 }
 
 class Component extends SvelteComponent {

test/js/samples/inline-style-optimized-multiple/expected.js

@@ -16,19 +16,19 @@ function create_fragment(ctx) {
 	return {
 		c() {
 			div = element("div");
-			set_style(div, "color", ctx.color);
-			set_style(div, "transform", "translate(" + ctx.x + "px," + ctx.y + "px)");
+			set_style(div, "color", /*color*/ ctx[0]);
+			set_style(div, "transform", "translate(" + /*x*/ ctx[1] + "px," + /*y*/ ctx[2] + "px)");
 		},
 		m(target, anchor) {
 			insert(target, div, anchor);
 		},
-		p(changed, ctx) {
-			if (changed.color) {
-				set_style(div, "color", ctx.color);
+		p(ctx, [dirty]) {
+			if (dirty & /*color*/ 1) {
+				set_style(div, "color", /*color*/ ctx[0]);
 			}
 
-			if (changed.x || changed.y) {
-				set_style(div, "transform", "translate(" + ctx.x + "px," + ctx.y + "px)");
+			if (dirty & /*x, y*/ 6) {
+				set_style(div, "transform", "translate(" + /*x*/ ctx[1] + "px," + /*y*/ ctx[2] + "px)");
 			}
 		},
 		i: noop,
@@ -45,18 +45,18 @@ function instance($$self, $$props, $$invalidate) {
 	let { y } = $$props;
 
 	$$self.$set = $$props => {
-		if ("color" in $$props) $$invalidate("color", color = $$props.color);
-		if ("x" in $$props) $$invalidate("x", x = $$props.x);
-		if ("y" in $$props) $$invalidate("y", y = $$props.y);
+		if ("color" in $$props) $$invalidate(0, color = $$props.color);
+		if ("x" in $$props) $$invalidate(1, x = $$props.x);
+		if ("y" in $$props) $$invalidate(2, y = $$props.y);
 	};
 
-	return { color, x, y };
+	return [color, x, y];
 }
 
 class Component extends SvelteComponent {
 	constructor(options) {
 		super();
-		init(this, options, instance, create_fragment, safe_not_equal, { color: 0, x: 0, y: 0 });
+		init(this, options, instance, create_fragment, safe_not_equal, { color: 0, x: 1, y: 2 });
 	}
 }
 

test/js/samples/inline-style-optimized-url/expected.js

@@ -16,14 +16,14 @@ function create_fragment(ctx) {
 	return {
 		c() {
 			div = element("div");
-			set_style(div, "background", "url(data:image/png;base64," + ctx.data + ")");
+			set_style(div, "background", "url(data:image/png;base64," + /*data*/ ctx[0] + ")");
 		},
 		m(target, anchor) {
 			insert(target, div, anchor);
 		},
-		p(changed, ctx) {
-			if (changed.data) {
-				set_style(div, "background", "url(data:image/png;base64," + ctx.data + ")");
+		p(ctx, [dirty]) {
+			if (dirty & /*data*/ 1) {
+				set_style(div, "background", "url(data:image/png;base64," + /*data*/ ctx[0] + ")");
 			}
 		},
 		i: noop,
@@ -38,10 +38,10 @@ function instance($$self, $$props, $$invalidate) {
 	let { data } = $$props;
 
 	$$self.$set = $$props => {
-		if ("data" in $$props) $$invalidate("data", data = $$props.data);
+		if ("data" in $$props) $$invalidate(0, data = $$props.data);
 	};
 
-	return { data };
+	return [data];
 }
 
 class Component extends SvelteComponent {

test/js/samples/inline-style-optimized/expected.js

@@ -16,14 +16,14 @@ function create_fragment(ctx) {
 	return {
 		c() {
 			div = element("div");
-			set_style(div, "color", ctx.color);
+			set_style(div, "color", /*color*/ ctx[0]);
 		},
 		m(target, anchor) {
 			insert(target, div, anchor);
 		},
-		p(changed, ctx) {
-			if (changed.color) {
-				set_style(div, "color", ctx.color);
+		p(ctx, [dirty]) {
+			if (dirty & /*color*/ 1) {
+				set_style(div, "color", /*color*/ ctx[0]);
 			}
 		},
 		i: noop,
@@ -38,10 +38,10 @@ function instance($$self, $$props, $$invalidate) {
 	let { color } = $$props;
 
 	$$self.$set = $$props => {
-		if ("color" in $$props) $$invalidate("color", color = $$props.color);
+		if ("color" in $$props) $$invalidate(0, color = $$props.color);
 	};
 
-	return { color };
+	return [color];
 }
 
 class Component extends SvelteComponent {

test/js/samples/inline-style-unoptimized/expected.js

@@ -22,20 +22,20 @@ function create_fragment(ctx) {
 			div0 = element("div");
 			t = space();
 			div1 = element("div");
-			attr(div0, "style", ctx.style);
-			attr(div1, "style", div1_style_value = "" + (ctx.key + ": " + ctx.value));
+			attr(div0, "style", /*style*/ ctx[0]);
+			attr(div1, "style", div1_style_value = "" + (/*key*/ ctx[1] + ": " + /*value*/ ctx[2]));
 		},
 		m(target, anchor) {
 			insert(target, div0, anchor);
 			insert(target, t, anchor);
 			insert(target, div1, anchor);
 		},
-		p(changed, ctx) {
-			if (changed.style) {
-				attr(div0, "style", ctx.style);
+		p(ctx, [dirty]) {
+			if (dirty & /*style*/ 1) {
+				attr(div0, "style", /*style*/ ctx[0]);
 			}
 
-			if ((changed.key || changed.value) && div1_style_value !== (div1_style_value = "" + (ctx.key + ": " + ctx.value))) {
+			if (dirty & /*key, value*/ 6 && div1_style_value !== (div1_style_value = "" + (/*key*/ ctx[1] + ": " + /*value*/ ctx[2]))) {
 				attr(div1, "style", div1_style_value);
 			}
 		},
@@ -55,18 +55,18 @@ function instance($$self, $$props, $$invalidate) {
 	let { value } = $$props;
 
 	$$self.$set = $$props => {
-		if ("style" in $$props) $$invalidate("style", style = $$props.style);
-		if ("key" in $$props) $$invalidate("key", key = $$props.key);
-		if ("value" in $$props) $$invalidate("value", value = $$props.value);
+		if ("style" in $$props) $$invalidate(0, style = $$props.style);
+		if ("key" in $$props) $$invalidate(1, key = $$props.key);
+		if ("value" in $$props) $$invalidate(2, value = $$props.value);
 	};
 
-	return { style, key, value };
+	return [style, key, value];
 }
 
 class Component extends SvelteComponent {
 	constructor(options) {
 		super();
-		init(this, options, instance, create_fragment, safe_not_equal, { style: 0, key: 0, value: 0 });
+		init(this, options, instance, create_fragment, safe_not_equal, { style: 0, key: 1, value: 2 });
 	}
 }
 

test/js/samples/input-files/expected.js

@@ -20,7 +20,7 @@ function create_fragment(ctx) {
 			input = element("input");
 			attr(input, "type", "file");
 			input.multiple = true;
-			dispose = listen(input, "change", ctx.input_change_handler);
+			dispose = listen(input, "change", /*input_change_handler*/ ctx[1]);
 		},
 		m(target, anchor) {
 			insert(target, input, anchor);
@@ -40,14 +40,14 @@ function instance($$self, $$props, $$invalidate) {
 
 	function input_change_handler() {
 		files = this.files;
-		$$invalidate("files", files);
+		$$invalidate(0, files);
 	}
 
 	$$self.$set = $$props => {
-		if ("files" in $$props) $$invalidate("files", files = $$props.files);
+		if ("files" in $$props) $$invalidate(0, files = $$props.files);
 	};
 
-	return { files, input_change_handler };
+	return [files, input_change_handler];
 }
 
 class Component extends SvelteComponent {

test/js/samples/input-no-initial-value/expected.js

@@ -33,20 +33,20 @@ function create_fragment(ctx) {
 			input.required = true;
 
 			dispose = [
-				listen(input, "input", ctx.input_input_handler),
-				listen(form, "submit", ctx.handleSubmit)
+				listen(input, "input", /*input_input_handler*/ ctx[2]),
+				listen(form, "submit", /*handleSubmit*/ ctx[1])
 			];
 		},
 		m(target, anchor) {
 			insert(target, form, anchor);
 			append(form, input);
-			set_input_value(input, ctx.test);
+			set_input_value(input, /*test*/ ctx[0]);
 			append(form, t0);
 			append(form, button);
 		},
-		p(changed, ctx) {
-			if (changed.test && input.value !== ctx.test) {
-				set_input_value(input, ctx.test);
+		p(ctx, [dirty]) {
+			if (dirty & /*test*/ 1 && input.value !== /*test*/ ctx[0]) {
+				set_input_value(input, /*test*/ ctx[0]);
 			}
 		},
 		i: noop,
@@ -68,10 +68,10 @@ function instance($$self, $$props, $$invalidate) {
 
 	function input_input_handler() {
 		test = this.value;
-		$$invalidate("test", test);
+		$$invalidate(0, test);
 	}
 
-	return { test, handleSubmit, input_input_handler };
+	return [test, handleSubmit, input_input_handler];
 }
 
 class Component extends SvelteComponent {

test/js/samples/input-range/expected.js

@@ -24,17 +24,17 @@ function create_fragment(ctx) {
 			attr(input, "type", "range");
 
 			dispose = [
-				listen(input, "change", ctx.input_change_input_handler),
-				listen(input, "input", ctx.input_change_input_handler)
+				listen(input, "change", /*input_change_input_handler*/ ctx[1]),
+				listen(input, "input", /*input_change_input_handler*/ ctx[1])
 			];
 		},
 		m(target, anchor) {
 			insert(target, input, anchor);
-			set_input_value(input, ctx.value);
+			set_input_value(input, /*value*/ ctx[0]);
 		},
-		p(changed, ctx) {
-			if (changed.value) {
-				set_input_value(input, ctx.value);
+		p(ctx, [dirty]) {
+			if (dirty & /*value*/ 1) {
+				set_input_value(input, /*value*/ ctx[0]);
 			}
 		},
 		i: noop,
@@ -51,14 +51,14 @@ function instance($$self, $$props, $$invalidate) {
 
 	function input_change_input_handler() {
 		value = to_number(this.value);
-		$$invalidate("value", value);
+		$$invalidate(0, value);
 	}
 
 	$$self.$set = $$props => {
-		if ("value" in $$props) $$invalidate("value", value = $$props.value);
+		if ("value" in $$props) $$invalidate(0, value = $$props.value);
 	};
 
-	return { value, input_change_input_handler };
+	return [value, input_change_input_handler];
 }
 
 class Component extends SvelteComponent {

test/js/samples/input-without-blowback-guard/expected.js

@@ -19,15 +19,15 @@ function create_fragment(ctx) {
 		c() {
 			input = element("input");
 			attr(input, "type", "checkbox");
-			dispose = listen(input, "change", ctx.input_change_handler);
+			dispose = listen(input, "change", /*input_change_handler*/ ctx[1]);
 		},
 		m(target, anchor) {
 			insert(target, input, anchor);
-			input.checked = ctx.foo;
+			input.checked = /*foo*/ ctx[0];
 		},
-		p(changed, ctx) {
-			if (changed.foo) {
-				input.checked = ctx.foo;
+		p(ctx, [dirty]) {
+			if (dirty & /*foo*/ 1) {
+				input.checked = /*foo*/ ctx[0];
 			}
 		},
 		i: noop,
@@ -44,14 +44,14 @@ function instance($$self, $$props, $$invalidate) {
 
 	function input_change_handler() {
 		foo = this.checked;
-		$$invalidate("foo", foo);
+		$$invalidate(0, foo);
 	}
 
 	$$self.$set = $$props => {
-		if ("foo" in $$props) $$invalidate("foo", foo = $$props.foo);
+		if ("foo" in $$props) $$invalidate(0, foo = $$props.foo);
 	};
 
-	return { foo, input_change_handler };
+	return [foo, input_change_handler];
 }
 
 class Component extends SvelteComponent {

test/js/samples/instrumentation-script-if-no-block/expected.js

@@ -29,8 +29,8 @@ function create_fragment(ctx) {
 			t1 = space();
 			p = element("p");
 			t2 = text("x: ");
-			t3 = text(ctx.x);
-			dispose = listen(button, "click", ctx.foo);
+			t3 = text(/*x*/ ctx[0]);
+			dispose = listen(button, "click", /*foo*/ ctx[1]);
 		},
 		m(target, anchor) {
 			insert(target, button, anchor);
@@ -39,8 +39,8 @@ function create_fragment(ctx) {
 			append(p, t2);
 			append(p, t3);
 		},
-		p(changed, ctx) {
-			if (changed.x) set_data(t3, ctx.x);
+		p(ctx, [dirty]) {
+			if (dirty & /*x*/ 1) set_data(t3, /*x*/ ctx[0]);
 		},
 		i: noop,
 		o: noop,
@@ -57,10 +57,10 @@ function instance($$self, $$props, $$invalidate) {
 	let x = 0;
 
 	function foo() {
-		if (true) $$invalidate("x", x += 1);
+		if (true) $$invalidate(0, x += 1);
 	}
 
-	return { x, foo };
+	return [x, foo];
 }
 
 class Component extends SvelteComponent {

test/js/samples/instrumentation-script-x-equals-x/expected.js

@@ -19,7 +19,7 @@ function create_fragment(ctx) {
 	let t1;
 	let p;
 	let t2;
-	let t3_value = ctx.things.length + "";
+	let t3_value = /*things*/ ctx[0].length + "";
 	let t3;
 	let dispose;
 
@@ -31,7 +31,7 @@ function create_fragment(ctx) {
 			p = element("p");
 			t2 = text("number of things: ");
 			t3 = text(t3_value);
-			dispose = listen(button, "click", ctx.foo);
+			dispose = listen(button, "click", /*foo*/ ctx[1]);
 		},
 		m(target, anchor) {
 			insert(target, button, anchor);
@@ -40,8 +40,8 @@ function create_fragment(ctx) {
 			append(p, t2);
 			append(p, t3);
 		},
-		p(changed, ctx) {
-			if (changed.things && t3_value !== (t3_value = ctx.things.length + "")) set_data(t3, t3_value);
+		p(ctx, [dirty]) {
+			if (dirty & /*things*/ 1 && t3_value !== (t3_value = /*things*/ ctx[0].length + "")) set_data(t3, t3_value);
 		},
 		i: noop,
 		o: noop,
@@ -59,10 +59,10 @@ function instance($$self, $$props, $$invalidate) {
 
 	function foo() {
 		things.push(1);
-		$$invalidate("things", things);
+		$$invalidate(0, things);
 	}
 
-	return { things, foo };
+	return [things, foo];
 }
 
 class Component extends SvelteComponent {

test/js/samples/instrumentation-template-if-no-block/expected.js

@@ -29,8 +29,8 @@ function create_fragment(ctx) {
 			t1 = space();
 			p = element("p");
 			t2 = text("x: ");
-			t3 = text(ctx.x);
-			dispose = listen(button, "click", ctx.click_handler);
+			t3 = text(/*x*/ ctx[0]);
+			dispose = listen(button, "click", /*click_handler*/ ctx[1]);
 		},
 		m(target, anchor) {
 			insert(target, button, anchor);
@@ -39,8 +39,8 @@ function create_fragment(ctx) {
 			append(p, t2);
 			append(p, t3);
 		},
-		p(changed, ctx) {
-			if (changed.x) set_data(t3, ctx.x);
+		p(ctx, [dirty]) {
+			if (dirty & /*x*/ 1) set_data(t3, /*x*/ ctx[0]);
 		},
 		i: noop,
 		o: noop,
@@ -57,10 +57,10 @@ function instance($$self, $$props, $$invalidate) {
 	let x = 0;
 
 	const click_handler = () => {
-		if (true) $$invalidate("x", x += 1);
+		if (true) $$invalidate(0, x += 1);
 	};
 
-	return { x, click_handler };
+	return [x, click_handler];
 }
 
 class Component extends SvelteComponent {

test/js/samples/instrumentation-template-x-equals-x/expected.js

@@ -19,7 +19,7 @@ function create_fragment(ctx) {
 	let t1;
 	let p;
 	let t2;
-	let t3_value = ctx.things.length + "";
+	let t3_value = /*things*/ ctx[0].length + "";
 	let t3;
 	let dispose;
 
@@ -31,7 +31,7 @@ function create_fragment(ctx) {
 			p = element("p");
 			t2 = text("number of things: ");
 			t3 = text(t3_value);
-			dispose = listen(button, "click", ctx.click_handler);
+			dispose = listen(button, "click", /*click_handler*/ ctx[1]);
 		},
 		m(target, anchor) {
 			insert(target, button, anchor);
@@ -40,8 +40,8 @@ function create_fragment(ctx) {
 			append(p, t2);
 			append(p, t3);
 		},
-		p(changed, ctx) {
-			if (changed.things && t3_value !== (t3_value = ctx.things.length + "")) set_data(t3, t3_value);
+		p(ctx, [dirty]) {
+			if (dirty & /*things*/ 1 && t3_value !== (t3_value = /*things*/ ctx[0].length + "")) set_data(t3, t3_value);
 		},
 		i: noop,
 		o: noop,
@@ -59,10 +59,10 @@ function instance($$self, $$props, $$invalidate) {
 
 	const click_handler = () => {
 		things.push(1);
-		$$invalidate("things", things);
+		$$invalidate(0, things);
 	};
 
-	return { things, click_handler };
+	return [things, click_handler];
 }
 
 class Component extends SvelteComponent {

test/js/samples/loop-protect/expected.js

@@ -89,7 +89,7 @@ function instance($$self) {
 		} while (true);
 	}
 
-	return {};
+	return [];
 }
 
 class Component extends SvelteComponentDev {

test/js/samples/media-bindings/expected.js

@@ -29,59 +29,59 @@ function create_fragment(ctx) {
 			audio_updating = true;
 		}
 
-		ctx.audio_timeupdate_handler.call(audio);
+		/*audio_timeupdate_handler*/ ctx[10].call(audio);
 	}
 
 	return {
 		c() {
 			audio = element("audio");
-			if (ctx.played === void 0 || ctx.currentTime === void 0 || ctx.ended === void 0) add_render_callback(audio_timeupdate_handler);
-			if (ctx.duration === void 0) add_render_callback(() => ctx.audio_durationchange_handler.call(audio));
-			if (ctx.buffered === void 0) add_render_callback(() => ctx.audio_progress_handler.call(audio));
-			if (ctx.buffered === void 0 || ctx.seekable === void 0) add_render_callback(() => ctx.audio_loadedmetadata_handler.call(audio));
-			if (ctx.seeking === void 0) add_render_callback(() => ctx.audio_seeking_seeked_handler.call(audio));
-			if (ctx.ended === void 0) add_render_callback(() => ctx.audio_ended_handler.call(audio));
+			if (/*played*/ ctx[2] === void 0 || /*currentTime*/ ctx[3] === void 0 || /*ended*/ ctx[9] === void 0) add_render_callback(audio_timeupdate_handler);
+			if (/*duration*/ ctx[4] === void 0) add_render_callback(() => /*audio_durationchange_handler*/ ctx[11].call(audio));
+			if (/*buffered*/ ctx[0] === void 0) add_render_callback(() => /*audio_progress_handler*/ ctx[13].call(audio));
+			if (/*buffered*/ ctx[0] === void 0 || /*seekable*/ ctx[1] === void 0) add_render_callback(() => /*audio_loadedmetadata_handler*/ ctx[14].call(audio));
+			if (/*seeking*/ ctx[8] === void 0) add_render_callback(() => /*audio_seeking_seeked_handler*/ ctx[17].call(audio));
+			if (/*ended*/ ctx[9] === void 0) add_render_callback(() => /*audio_ended_handler*/ ctx[18].call(audio));
 
 			dispose = [
 				listen(audio, "timeupdate", audio_timeupdate_handler),
-				listen(audio, "durationchange", ctx.audio_durationchange_handler),
-				listen(audio, "play", ctx.audio_play_pause_handler),
-				listen(audio, "pause", ctx.audio_play_pause_handler),
-				listen(audio, "progress", ctx.audio_progress_handler),
-				listen(audio, "loadedmetadata", ctx.audio_loadedmetadata_handler),
-				listen(audio, "volumechange", ctx.audio_volumechange_handler),
-				listen(audio, "ratechange", ctx.audio_ratechange_handler),
-				listen(audio, "seeking", ctx.audio_seeking_seeked_handler),
-				listen(audio, "seeked", ctx.audio_seeking_seeked_handler),
-				listen(audio, "ended", ctx.audio_ended_handler)
+				listen(audio, "durationchange", /*audio_durationchange_handler*/ ctx[11]),
+				listen(audio, "play", /*audio_play_pause_handler*/ ctx[12]),
+				listen(audio, "pause", /*audio_play_pause_handler*/ ctx[12]),
+				listen(audio, "progress", /*audio_progress_handler*/ ctx[13]),
+				listen(audio, "loadedmetadata", /*audio_loadedmetadata_handler*/ ctx[14]),
+				listen(audio, "volumechange", /*audio_volumechange_handler*/ ctx[15]),
+				listen(audio, "ratechange", /*audio_ratechange_handler*/ ctx[16]),
+				listen(audio, "seeking", /*audio_seeking_seeked_handler*/ ctx[17]),
+				listen(audio, "seeked", /*audio_seeking_seeked_handler*/ ctx[17]),
+				listen(audio, "ended", /*audio_ended_handler*/ ctx[18])
 			];
 		},
 		m(target, anchor) {
 			insert(target, audio, anchor);
 
-			if (!isNaN(ctx.volume)) {
-				audio.volume = ctx.volume;
+			if (!isNaN(/*volume*/ ctx[6])) {
+				audio.volume = /*volume*/ ctx[6];
 			}
 
-			if (!isNaN(ctx.playbackRate)) {
-				audio.playbackRate = ctx.playbackRate;
+			if (!isNaN(/*playbackRate*/ ctx[7])) {
+				audio.playbackRate = /*playbackRate*/ ctx[7];
 			}
 		},
-		p(changed, ctx) {
-			if (!audio_updating && changed.currentTime && !isNaN(ctx.currentTime)) {
-				audio.currentTime = ctx.currentTime;
+		p(ctx, [dirty]) {
+			if (!audio_updating && dirty & /*currentTime*/ 8 && !isNaN(/*currentTime*/ ctx[3])) {
+				audio.currentTime = /*currentTime*/ ctx[3];
 			}
 
-			if (changed.paused && audio_is_paused !== (audio_is_paused = ctx.paused)) {
+			if (dirty & /*paused*/ 32 && audio_is_paused !== (audio_is_paused = /*paused*/ ctx[5])) {
 				audio[audio_is_paused ? "pause" : "play"]();
 			}
 
-			if (changed.volume && !isNaN(ctx.volume)) {
-				audio.volume = ctx.volume;
+			if (dirty & /*volume*/ 64 && !isNaN(/*volume*/ ctx[6])) {
+				audio.volume = /*volume*/ ctx[6];
 			}
 
-			if (changed.playbackRate && !isNaN(ctx.playbackRate)) {
-				audio.playbackRate = ctx.playbackRate;
+			if (dirty & /*playbackRate*/ 128 && !isNaN(/*playbackRate*/ ctx[7])) {
+				audio.playbackRate = /*playbackRate*/ ctx[7];
 			}
 
 			audio_updating = false;
@@ -111,67 +111,67 @@ function instance($$self, $$props, $$invalidate) {
 		played = time_ranges_to_array(this.played);
 		currentTime = this.currentTime;
 		ended = this.ended;
-		$$invalidate("played", played);
-		$$invalidate("currentTime", currentTime);
-		$$invalidate("ended", ended);
+		$$invalidate(2, played);
+		$$invalidate(3, currentTime);
+		$$invalidate(9, ended);
 	}
 
 	function audio_durationchange_handler() {
 		duration = this.duration;
-		$$invalidate("duration", duration);
+		$$invalidate(4, duration);
 	}
 
 	function audio_play_pause_handler() {
 		paused = this.paused;
-		$$invalidate("paused", paused);
+		$$invalidate(5, paused);
 	}
 
 	function audio_progress_handler() {
 		buffered = time_ranges_to_array(this.buffered);
-		$$invalidate("buffered", buffered);
+		$$invalidate(0, buffered);
 	}
 
 	function audio_loadedmetadata_handler() {
 		buffered = time_ranges_to_array(this.buffered);
 		seekable = time_ranges_to_array(this.seekable);
-		$$invalidate("buffered", buffered);
-		$$invalidate("seekable", seekable);
+		$$invalidate(0, buffered);
+		$$invalidate(1, seekable);
 	}
 
 	function audio_volumechange_handler() {
 		volume = this.volume;
-		$$invalidate("volume", volume);
+		$$invalidate(6, volume);
 	}
 
 	function audio_ratechange_handler() {
 		playbackRate = this.playbackRate;
-		$$invalidate("playbackRate", playbackRate);
+		$$invalidate(7, playbackRate);
 	}
 
 	function audio_seeking_seeked_handler() {
 		seeking = this.seeking;
-		$$invalidate("seeking", seeking);
+		$$invalidate(8, seeking);
 	}
 
 	function audio_ended_handler() {
 		ended = this.ended;
-		$$invalidate("ended", ended);
+		$$invalidate(9, ended);
 	}
 
 	$$self.$set = $$props => {
-		if ("buffered" in $$props) $$invalidate("buffered", buffered = $$props.buffered);
-		if ("seekable" in $$props) $$invalidate("seekable", seekable = $$props.seekable);
-		if ("played" in $$props) $$invalidate("played", played = $$props.played);
-		if ("currentTime" in $$props) $$invalidate("currentTime", currentTime = $$props.currentTime);
-		if ("duration" in $$props) $$invalidate("duration", duration = $$props.duration);
-		if ("paused" in $$props) $$invalidate("paused", paused = $$props.paused);
-		if ("volume" in $$props) $$invalidate("volume", volume = $$props.volume);
-		if ("playbackRate" in $$props) $$invalidate("playbackRate", playbackRate = $$props.playbackRate);
-		if ("seeking" in $$props) $$invalidate("seeking", seeking = $$props.seeking);
-		if ("ended" in $$props) $$invalidate("ended", ended = $$props.ended);
+		if ("buffered" in $$props) $$invalidate(0, buffered = $$props.buffered);
+		if ("seekable" in $$props) $$invalidate(1, seekable = $$props.seekable);
+		if ("played" in $$props) $$invalidate(2, played = $$props.played);
+		if ("currentTime" in $$props) $$invalidate(3, currentTime = $$props.currentTime);
+		if ("duration" in $$props) $$invalidate(4, duration = $$props.duration);
+		if ("paused" in $$props) $$invalidate(5, paused = $$props.paused);
+		if ("volume" in $$props) $$invalidate(6, volume = $$props.volume);
+		if ("playbackRate" in $$props) $$invalidate(7, playbackRate = $$props.playbackRate);
+		if ("seeking" in $$props) $$invalidate(8, seeking = $$props.seeking);
+		if ("ended" in $$props) $$invalidate(9, ended = $$props.ended);
 	};
 
-	return {
+	return [
 		buffered,
 		seekable,
 		played,
@@ -191,7 +191,7 @@ function instance($$self, $$props, $$invalidate) {
 		audio_ratechange_handler,
 		audio_seeking_seeked_handler,
 		audio_ended_handler
-	};
+	];
 }
 
 class Component extends SvelteComponent {
@@ -200,15 +200,15 @@ class Component extends SvelteComponent {
 
 		init(this, options, instance, create_fragment, safe_not_equal, {
 			buffered: 0,
-			seekable: 0,
-			played: 0,
-			currentTime: 0,
-			duration: 0,
-			paused: 0,
-			volume: 0,
-			playbackRate: 0,
-			seeking: 0,
-			ended: 0
+			seekable: 1,
+			played: 2,
+			currentTime: 3,
+			duration: 4,
+			paused: 5,
+			volume: 6,
+			playbackRate: 7,
+			seeking: 8,
+			ended: 9
 		});
 	}
 }

test/js/samples/reactive-values-non-topologically-ordered/expected.js

@@ -7,20 +7,20 @@ function instance($$self, $$props, $$invalidate) {
 	let b;
 
 	$$self.$set = $$props => {
-		if ("x" in $$props) $$invalidate("x", x = $$props.x);
+		if ("x" in $$props) $$invalidate(0, x = $$props.x);
 	};
 
-	$$self.$$.update = (changed = { x: 1, b: 1 }) => {
-		if (changed.x) {
-			$: $$invalidate("b", b = x);
+	$$self.$$.update = () => {
+		if ($$self.$$.dirty & /*x*/ 1) {
+			$: $$invalidate(2, b = x);
 		}
 
-		if (changed.b) {
+		if ($$self.$$.dirty & /*b*/ 4) {
 			$: a = b;
 		}
 	};
 
-	return { x };
+	return [x];
 }
 
 class Component extends SvelteComponent {

test/js/samples/reactive-values-non-writable-dependencies/expected.js

@@ -6,23 +6,23 @@ function instance($$self, $$props, $$invalidate) {
 	let { b = 2 } = $$props;
 
 	$$self.$set = $$props => {
-		if ("a" in $$props) $$invalidate("a", a = $$props.a);
-		if ("b" in $$props) $$invalidate("b", b = $$props.b);
+		if ("a" in $$props) $$invalidate(0, a = $$props.a);
+		if ("b" in $$props) $$invalidate(1, b = $$props.b);
 	};
 
-	$$self.$$.update = (changed = { a: 1, b: 1 }) => {
-		if (changed.a || changed.b) {
+	$$self.$$.update = () => {
+		if ($$self.$$.dirty & /*a, b*/ 3) {
 			$: console.log("max", Math.max(a, b));
 		}
 	};
 
-	return { a, b };
+	return [a, b];
 }
 
 class Component extends SvelteComponent {
 	constructor(options) {
 		super();
-		init(this, options, instance, null, safe_not_equal, { a: 0, b: 0 });
+		init(this, options, instance, null, safe_not_equal, { a: 0, b: 1 });
 	}
 }
 

test/js/samples/select-dynamic-value/expected.js

@@ -32,7 +32,7 @@ function create_fragment(ctx) {
 			insert(target, select, anchor);
 			append(select, option0);
 			append(select, option1);
-			select_value_value = ctx.current;
+			select_value_value = /*current*/ ctx[0];
 
 			for (var i = 0; i < select.options.length; i += 1) {
 				var option = select.options[i];
@@ -43,8 +43,8 @@ function create_fragment(ctx) {
 				}
 			}
 		},
-		p(changed, ctx) {
-			if (changed.current && select_value_value !== (select_value_value = ctx.current)) {
+		p(ctx, [dirty]) {
+			if (dirty & /*current*/ 1 && select_value_value !== (select_value_value = /*current*/ ctx[0])) {
 				for (var i = 0; i < select.options.length; i += 1) {
 					var option = select.options[i];
 
@@ -67,10 +67,10 @@ function instance($$self, $$props, $$invalidate) {
 	let { current } = $$props;
 
 	$$self.$set = $$props => {
-		if ("current" in $$props) $$invalidate("current", current = $$props.current);
+		if ("current" in $$props) $$invalidate(0, current = $$props.current);
 	};
 
-	return { current };
+	return [current];
 }
 
 class Component extends SvelteComponent {

test/js/samples/setup-method/expected.js

@@ -7,10 +7,14 @@ function foo(bar) {
 	console.log(bar);
 }
 
+function instance($$self, $$props, $$invalidate) {
+	return [foo];
+}
+
 class Component extends SvelteComponent {
 	constructor(options) {
 		super();
-		init(this, options, null, null, safe_not_equal, { foo: 0 });
+		init(this, options, instance, null, safe_not_equal, { foo: 0 });
 	}
 
 	get foo() {

test/js/samples/src-attribute-check/expected.js

@@ -35,21 +35,21 @@ function create_fragment(ctx) {
 		},
 		h() {
 			attr(img0, "alt", "potato");
-			if (img0.src !== (img0_src_value = ctx.url)) attr(img0, "src", img0_src_value);
+			if (img0.src !== (img0_src_value = /*url*/ ctx[0])) attr(img0, "src", img0_src_value);
 			attr(img1, "alt", "potato");
-			if (img1.src !== (img1_src_value = "" + (ctx.slug + ".jpg"))) attr(img1, "src", img1_src_value);
+			if (img1.src !== (img1_src_value = "" + (/*slug*/ ctx[1] + ".jpg"))) attr(img1, "src", img1_src_value);
 		},
 		m(target, anchor) {
 			insert(target, img0, anchor);
 			insert(target, t, anchor);
 			insert(target, img1, anchor);
 		},
-		p(changed, ctx) {
-			if (changed.url && img0.src !== (img0_src_value = ctx.url)) {
+		p(ctx, [dirty]) {
+			if (dirty & /*url*/ 1 && img0.src !== (img0_src_value = /*url*/ ctx[0])) {
 				attr(img0, "src", img0_src_value);
 			}
 
-			if (changed.slug && img1.src !== (img1_src_value = "" + (ctx.slug + ".jpg"))) {
+			if (dirty & /*slug*/ 2 && img1.src !== (img1_src_value = "" + (/*slug*/ ctx[1] + ".jpg"))) {
 				attr(img1, "src", img1_src_value);
 			}
 		},
@@ -68,17 +68,17 @@ function instance($$self, $$props, $$invalidate) {
 	let { slug } = $$props;
 
 	$$self.$set = $$props => {
-		if ("url" in $$props) $$invalidate("url", url = $$props.url);
-		if ("slug" in $$props) $$invalidate("slug", slug = $$props.slug);
+		if ("url" in $$props) $$invalidate(0, url = $$props.url);
+		if ("slug" in $$props) $$invalidate(1, slug = $$props.slug);
 	};
 
-	return { url, slug };
+	return [url, slug];
 }
 
 class Component extends SvelteComponent {
 	constructor(options) {
 		super();
-		init(this, options, instance, create_fragment, safe_not_equal, { url: 0, slug: 0 });
+		init(this, options, instance, create_fragment, safe_not_equal, { url: 0, slug: 1 });
 	}
 }
 

test/js/samples/title/expected.js

@@ -3,13 +3,13 @@ import { SvelteComponent, init, noop, safe_not_equal } from "svelte/internal";
 
 function create_fragment(ctx) {
 	let title_value;
-	document.title = title_value = "a " + ctx.custom + " title";
+	document.title = title_value = "a " + /*custom*/ ctx[0] + " title";
 
 	return {
 		c: noop,
 		m: noop,
-		p(changed, ctx) {
-			if (changed.custom && title_value !== (title_value = "a " + ctx.custom + " title")) {
+		p(ctx, [dirty]) {
+			if (dirty & /*custom*/ 1 && title_value !== (title_value = "a " + /*custom*/ ctx[0] + " title")) {
 				document.title = title_value;
 			}
 		},
@@ -23,10 +23,10 @@ function instance($$self, $$props, $$invalidate) {
 	let { custom } = $$props;
 
 	$$self.$set = $$props => {
-		if ("custom" in $$props) $$invalidate("custom", custom = $$props.custom);
+		if ("custom" in $$props) $$invalidate(0, custom = $$props.custom);
 	};
 
-	return { custom };
+	return [custom];
 }
 
 class Component extends SvelteComponent {

test/js/samples/transition-local/expected.js

@@ -15,7 +15,7 @@ import {
 
 function create_if_block(ctx) {
 	let if_block_anchor;
-	let if_block = ctx.y && create_if_block_1(ctx);
+	let if_block = /*y*/ ctx[1] && create_if_block_1(ctx);
 
 	return {
 		c() {
@@ -26,8 +26,8 @@ function create_if_block(ctx) {
 			if (if_block) if_block.m(target, anchor);
 			insert(target, if_block_anchor, anchor);
 		},
-		p(changed, ctx) {
-			if (ctx.y) {
+		p(ctx, dirty) {
+			if (/*y*/ ctx[1]) {
 				if (!if_block) {
 					if_block = create_if_block_1(ctx);
 					if_block.c();
@@ -80,7 +80,7 @@ function create_if_block_1(ctx) {
 
 function create_fragment(ctx) {
 	let if_block_anchor;
-	let if_block = ctx.x && create_if_block(ctx);
+	let if_block = /*x*/ ctx[0] && create_if_block(ctx);
 
 	return {
 		c() {
@@ -91,10 +91,10 @@ function create_fragment(ctx) {
 			if (if_block) if_block.m(target, anchor);
 			insert(target, if_block_anchor, anchor);
 		},
-		p(changed, ctx) {
-			if (ctx.x) {
+		p(ctx, [dirty]) {
+			if (/*x*/ ctx[0]) {
 				if (if_block) {
-					if_block.p(changed, ctx);
+					if_block.p(ctx, dirty);
 				} else {
 					if_block = create_if_block(ctx);
 					if_block.c();
@@ -123,17 +123,17 @@ function instance($$self, $$props, $$invalidate) {
 	let { y } = $$props;
 
 	$$self.$set = $$props => {
-		if ("x" in $$props) $$invalidate("x", x = $$props.x);
-		if ("y" in $$props) $$invalidate("y", y = $$props.y);
+		if ("x" in $$props) $$invalidate(0, x = $$props.x);
+		if ("y" in $$props) $$invalidate(1, y = $$props.y);
 	};
 
-	return { x, y };
+	return [x, y];
 }
 
 class Component extends SvelteComponent {
 	constructor(options) {
 		super();
-		init(this, options, instance, create_fragment, safe_not_equal, { x: 0, y: 0 });
+		init(this, options, instance, create_fragment, safe_not_equal, { x: 0, y: 1 });
 	}
 }
 

test/js/samples/transition-repeated-outro/expected.js

@@ -49,7 +49,7 @@ function create_if_block(ctx) {
 function create_fragment(ctx) {
 	let if_block_anchor;
 	let current;
-	let if_block = ctx.num < 5 && create_if_block(ctx);
+	let if_block = /*num*/ ctx[0] < 5 && create_if_block(ctx);
 
 	return {
 		c() {
@@ -61,8 +61,8 @@ function create_fragment(ctx) {
 			insert(target, if_block_anchor, anchor);
 			current = true;
 		},
-		p(changed, ctx) {
-			if (ctx.num < 5) {
+		p(ctx, [dirty]) {
+			if (/*num*/ ctx[0] < 5) {
 				if (!if_block) {
 					if_block = create_if_block(ctx);
 					if_block.c();
@@ -101,10 +101,10 @@ function instance($$self, $$props, $$invalidate) {
 	let { num = 1 } = $$props;
 
 	$$self.$set = $$props => {
-		if ("num" in $$props) $$invalidate("num", num = $$props.num);
+		if ("num" in $$props) $$invalidate(0, num = $$props.num);
 	};
 
-	return { num };
+	return [num];
 }
 
 class Component extends SvelteComponent {

test/js/samples/unchanged-expression/expected.js

@@ -41,7 +41,7 @@ function create_fragment(ctx) {
 			div1 = element("div");
 			p3 = element("p");
 			t8 = text("Hello ");
-			t9 = text(ctx.world3);
+			t9 = text(/*world3*/ ctx[0]);
 		},
 		m(target, anchor) {
 			insert(target, div0, anchor);
@@ -56,8 +56,8 @@ function create_fragment(ctx) {
 			append(p3, t8);
 			append(p3, t9);
 		},
-		p(changed, ctx) {
-			if (changed.world3) set_data(t9, ctx.world3);
+		p(ctx, [dirty]) {
+			if (dirty & /*world3*/ 1) set_data(t9, /*world3*/ ctx[0]);
 		},
 		i: noop,
 		o: noop,
@@ -76,10 +76,10 @@ function instance($$self, $$props, $$invalidate) {
 	const world3 = "world";
 
 	function foo() {
-		$$invalidate("world3", world3 = "svelte");
+		$$invalidate(0, world3 = "svelte");
 	}
 
-	return { world3 };
+	return [world3];
 }
 
 class Component extends SvelteComponent {

test/js/samples/unreferenced-state-not-invalidated/expected.js

@@ -21,14 +21,14 @@ function create_fragment(ctx) {
 	return {
 		c() {
 			p = element("p");
-			t = text(ctx.y);
+			t = text(/*y*/ ctx[0]);
 		},
 		m(target, anchor) {
 			insert(target, p, anchor);
 			append(p, t);
 		},
-		p(changed, ctx) {
-			if (changed.y) set_data(t, ctx.y);
+		p(ctx, [dirty]) {
+			if (dirty & /*y*/ 1) set_data(t, /*y*/ ctx[0]);
 		},
 		i: noop,
 		o: noop,
@@ -39,12 +39,12 @@ function create_fragment(ctx) {
 }
 
 function instance($$self, $$props, $$invalidate) {
-	let a, b, c;
+	let a = 1, b = 2, c = 3;
 
 	onMount(() => {
 		const interval = setInterval(
 			() => {
-				$$invalidate("b", b += 1);
+				$$invalidate(1, b += 1);
 				c += 1;
 				console.log(b, c);
 			},
@@ -57,17 +57,14 @@ function instance($$self, $$props, $$invalidate) {
 	let x;
 	let y;
 
-	$$self.$$.update = (changed = { a: 1, b: 1 }) => {
-		if (changed.a) {
-			$: x = a * 2;
-		}
-
-		if (changed.b) {
-			$: $$invalidate("y", y = b * 2);
+	$$self.$$.update = () => {
+		if ($$self.$$.dirty & /*b*/ 2) {
+			$: $$invalidate(0, y = b * 2);
 		}
 	};
 
-	return { y };
+	$: x = a * 2;
+	return [y];
 }
 
 class Component extends SvelteComponent {

test/js/samples/unreferenced-state-not-invalidated/input.svelte

@@ -1,7 +1,7 @@
 <script>
 	import { onMount } from 'svelte';
 
-	let a, b, c;
+	let a = 1, b = 2, c = 3;
 
 	onMount(() => {
 		const interval = setInterval(() => {

test/js/samples/use-elements-as-anchors/expected.js

@@ -112,11 +112,11 @@ function create_fragment(ctx) {
 	let t6;
 	let t7;
 	let if_block4_anchor;
-	let if_block0 = ctx.a && create_if_block_4(ctx);
-	let if_block1 = ctx.b && create_if_block_3(ctx);
-	let if_block2 = ctx.c && create_if_block_2(ctx);
-	let if_block3 = ctx.d && create_if_block_1(ctx);
-	let if_block4 = ctx.e && create_if_block(ctx);
+	let if_block0 = /*a*/ ctx[0] && create_if_block_4(ctx);
+	let if_block1 = /*b*/ ctx[1] && create_if_block_3(ctx);
+	let if_block2 = /*c*/ ctx[2] && create_if_block_2(ctx);
+	let if_block3 = /*d*/ ctx[3] && create_if_block_1(ctx);
+	let if_block4 = /*e*/ ctx[4] && create_if_block(ctx);
 
 	return {
 		c() {
@@ -155,8 +155,8 @@ function create_fragment(ctx) {
 			if (if_block4) if_block4.m(target, anchor);
 			insert(target, if_block4_anchor, anchor);
 		},
-		p(changed, ctx) {
-			if (ctx.a) {
+		p(ctx, [dirty]) {
+			if (/*a*/ ctx[0]) {
 				if (!if_block0) {
 					if_block0 = create_if_block_4(ctx);
 					if_block0.c();
@@ -169,7 +169,7 @@ function create_fragment(ctx) {
 				if_block0 = null;
 			}
 
-			if (ctx.b) {
+			if (/*b*/ ctx[1]) {
 				if (!if_block1) {
 					if_block1 = create_if_block_3(ctx);
 					if_block1.c();
@@ -182,7 +182,7 @@ function create_fragment(ctx) {
 				if_block1 = null;
 			}
 
-			if (ctx.c) {
+			if (/*c*/ ctx[2]) {
 				if (!if_block2) {
 					if_block2 = create_if_block_2(ctx);
 					if_block2.c();
@@ -195,7 +195,7 @@ function create_fragment(ctx) {
 				if_block2 = null;
 			}
 
-			if (ctx.d) {
+			if (/*d*/ ctx[3]) {
 				if (!if_block3) {
 					if_block3 = create_if_block_1(ctx);
 					if_block3.c();
@@ -208,7 +208,7 @@ function create_fragment(ctx) {
 				if_block3 = null;
 			}
 
-			if (ctx.e) {
+			if (/*e*/ ctx[4]) {
 				if (!if_block4) {
 					if_block4 = create_if_block(ctx);
 					if_block4.c();
@@ -244,20 +244,20 @@ function instance($$self, $$props, $$invalidate) {
 	let { e } = $$props;
 
 	$$self.$set = $$props => {
-		if ("a" in $$props) $$invalidate("a", a = $$props.a);
-		if ("b" in $$props) $$invalidate("b", b = $$props.b);
-		if ("c" in $$props) $$invalidate("c", c = $$props.c);
-		if ("d" in $$props) $$invalidate("d", d = $$props.d);
-		if ("e" in $$props) $$invalidate("e", e = $$props.e);
+		if ("a" in $$props) $$invalidate(0, a = $$props.a);
+		if ("b" in $$props) $$invalidate(1, b = $$props.b);
+		if ("c" in $$props) $$invalidate(2, c = $$props.c);
+		if ("d" in $$props) $$invalidate(3, d = $$props.d);
+		if ("e" in $$props) $$invalidate(4, e = $$props.e);
 	};
 
-	return { a, b, c, d, e };
+	return [a, b, c, d, e];
 }
 
 class Component extends SvelteComponent {
 	constructor(options) {
 		super();
-		init(this, options, instance, create_fragment, safe_not_equal, { a: 0, b: 0, c: 0, d: 0, e: 0 });
+		init(this, options, instance, create_fragment, safe_not_equal, { a: 0, b: 1, c: 2, d: 3, e: 4 });
 	}
 }
 

test/js/samples/video-bindings/expected.js

@@ -29,27 +29,27 @@ function create_fragment(ctx) {
 			video_updating = true;
 		}
 
-		ctx.video_timeupdate_handler.call(video);
+		/*video_timeupdate_handler*/ ctx[5].call(video);
 	}
 
 	return {
 		c() {
 			video = element("video");
-			add_render_callback(() => ctx.video_elementresize_handler.call(video));
-			if (ctx.videoHeight === void 0 || ctx.videoWidth === void 0) add_render_callback(() => ctx.video_resize_handler.call(video));
+			add_render_callback(() => /*video_elementresize_handler*/ ctx[4].call(video));
+			if (/*videoHeight*/ ctx[1] === void 0 || /*videoWidth*/ ctx[2] === void 0) add_render_callback(() => /*video_resize_handler*/ ctx[6].call(video));
 
 			dispose = [
 				listen(video, "timeupdate", video_timeupdate_handler),
-				listen(video, "resize", ctx.video_resize_handler)
+				listen(video, "resize", /*video_resize_handler*/ ctx[6])
 			];
 		},
 		m(target, anchor) {
 			insert(target, video, anchor);
-			video_resize_listener = add_resize_listener(video, ctx.video_elementresize_handler.bind(video));
+			video_resize_listener = add_resize_listener(video, /*video_elementresize_handler*/ ctx[4].bind(video));
 		},
-		p(changed, ctx) {
-			if (!video_updating && changed.currentTime && !isNaN(ctx.currentTime)) {
-				video.currentTime = ctx.currentTime;
+		p(ctx, [dirty]) {
+			if (!video_updating && dirty & /*currentTime*/ 1 && !isNaN(/*currentTime*/ ctx[0])) {
+				video.currentTime = /*currentTime*/ ctx[0];
 			}
 
 			video_updating = false;
@@ -72,29 +72,29 @@ function instance($$self, $$props, $$invalidate) {
 
 	function video_elementresize_handler() {
 		offsetWidth = this.offsetWidth;
-		$$invalidate("offsetWidth", offsetWidth);
+		$$invalidate(3, offsetWidth);
 	}
 
 	function video_timeupdate_handler() {
 		currentTime = this.currentTime;
-		$$invalidate("currentTime", currentTime);
+		$$invalidate(0, currentTime);
 	}
 
 	function video_resize_handler() {
 		videoHeight = this.videoHeight;
 		videoWidth = this.videoWidth;
-		$$invalidate("videoHeight", videoHeight);
-		$$invalidate("videoWidth", videoWidth);
+		$$invalidate(1, videoHeight);
+		$$invalidate(2, videoWidth);
 	}
 
 	$$self.$set = $$props => {
-		if ("currentTime" in $$props) $$invalidate("currentTime", currentTime = $$props.currentTime);
-		if ("videoHeight" in $$props) $$invalidate("videoHeight", videoHeight = $$props.videoHeight);
-		if ("videoWidth" in $$props) $$invalidate("videoWidth", videoWidth = $$props.videoWidth);
-		if ("offsetWidth" in $$props) $$invalidate("offsetWidth", offsetWidth = $$props.offsetWidth);
+		if ("currentTime" in $$props) $$invalidate(0, currentTime = $$props.currentTime);
+		if ("videoHeight" in $$props) $$invalidate(1, videoHeight = $$props.videoHeight);
+		if ("videoWidth" in $$props) $$invalidate(2, videoWidth = $$props.videoWidth);
+		if ("offsetWidth" in $$props) $$invalidate(3, offsetWidth = $$props.offsetWidth);
 	};
 
-	return {
+	return [
 		currentTime,
 		videoHeight,
 		videoWidth,
@@ -102,7 +102,7 @@ function instance($$self, $$props, $$invalidate) {
 		video_elementresize_handler,
 		video_timeupdate_handler,
 		video_resize_handler
-	};
+	];
 }
 
 class Component extends SvelteComponent {
@@ -111,9 +111,9 @@ class Component extends SvelteComponent {
 
 		init(this, options, instance, create_fragment, safe_not_equal, {
 			currentTime: 0,
-			videoHeight: 0,
-			videoWidth: 0,
-			offsetWidth: 0
+			videoHeight: 1,
+			videoWidth: 2,
+			offsetWidth: 3
 		});
 	}
 }