differentiate between mutated and reassigned

src/Stats.ts

@@ -99,7 +99,7 @@ export default class Stats {
 		return {
 			timings,
 			warnings: this.warnings,
-			vars: component.vars.filter(variable => !variable.global && !variable.implicit).map(variable => ({
+			vars: component.vars.filter(variable => !variable.global && !variable.implicit && !variable.internal).map(variable => ({
 				name: variable.name,
 				export_name: variable.export_name || null,
 				injected: variable.injected || false,

src/compile/Component.ts

@@ -429,28 +429,16 @@ export default class Component {
 
 			if (node.type === 'ExportNamedDeclaration') {
 				if (node.declaration) {
-					const { kind } = node.declaration;
-
 					if (node.declaration.type === 'VariableDeclaration') {
 						node.declaration.declarations.forEach(declarator => {
 							extractNames(declarator.id).forEach(name => {
 								const variable = this.var_lookup.get(name);
 								variable.export_name = name;
-								if (kind !== 'const') variable.mutated = true;
 							});
 						});
 					} else {
 						const { name } = node.declaration.id;
 
-						const kind = node.declaration.type === 'ClassDeclaration'
-							? 'class'
-							: node.declaration.type === 'FunctionDeclaration'
-								? 'function'
-								: null;
-
-						// sanity check
-						if (!kind) throw new Error(`Unknown declaration type ${node.declaration.type}`);
-
 						const variable = this.var_lookup.get(name);
 						variable.export_name = name;
 					}
@@ -636,13 +624,17 @@ export default class Component {
 
 		walk(this.ast.instance.content, {
 			enter(node, parent) {
-				let names;
 				if (map.has(node)) {
 					scope = map.get(node);
 				}
 
+				let names;
+				let deep = false;
+
 				if (node.type === 'AssignmentExpression') {
-					names = node.left.type === 'MemberExpression'
+					deep = node.left.type === 'MemberExpression';
+
+					names = deep
 						? [getObject(node.left).name]
 						: extractNames(node.left);
 				} else if (node.type === 'UpdateExpression') {
@@ -653,7 +645,7 @@ export default class Component {
 					names.forEach(name => {
 						if (scope.findOwner(name) === instance_scope) {
 							const variable = component.var_lookup.get(name);
-							variable.mutated = true;
+							variable[deep ? 'mutated' : 'reassigned'] = true;
 						}
 					});
 				}
@@ -836,7 +828,7 @@ export default class Component {
 
 		this.ast.instance.content.body.forEach(node => {
 			if (node.type === 'VariableDeclaration') {
-				if (node.declarations.every(d => d.init && d.init.type === 'Literal' && !this.var_lookup.get(d.id.name).mutated)) {
+				if (node.declarations.every(d => d.init && d.init.type === 'Literal' && !this.var_lookup.get(d.id.name).reassigned)) {
 					node.declarations.forEach(d => {
 						const variable = this.var_lookup.get(d.id.name);
 						variable.hoistable = true;

src/compile/nodes/Binding.ts

@@ -34,11 +34,11 @@ export default class Binding extends Node {
 		if (this.isContextual) {
 			scope.dependenciesForName.get(name).forEach(name => {
 				const variable = component.var_lookup.get(name);
-				variable.mutated = true;
+				variable[this.expression.node.type === 'MemberExpression' ? 'mutated' : 'reassigned'] = true;
 			});
 		} else {
 			const variable = component.var_lookup.get(name);
-			variable.mutated = true;
+			variable[this.expression.node.type === 'MemberExpression' ? 'mutated' : 'reassigned'] = true;
 		}
 
 		if (this.expression.node.type === 'MemberExpression') {

src/compile/nodes/EventHandler.ts

@@ -44,7 +44,7 @@ export default class EventHandler extends Node {
 
 			component.add_var({
 				name,
-				injected: true,
+				internal: true,
 				referenced: true
 			});
 

src/compile/nodes/shared/Expression.ts

@@ -149,30 +149,33 @@ export default class Expression {
 				}
 
 				// track any assignments from template expressions as mutable
-				let mutated;
+				let names;
+				let deep = false;
+
 				if (function_expression) {
 					if (node.type === 'AssignmentExpression') {
-						mutated = node.left.type === 'MemberExpression'
+						deep = node.left.type === 'MemberExpression';
+						names = deep
 							? [getObject(node.left).name]
 							: extractNames(node.left);
 					} else if (node.type === 'UpdateExpression') {
 						const { name } = getObject(node.argument);
-						mutated = [name];
+						names = [name];
 					}
 				}
 
-				if (mutated) {
+				if (names) {
-					mutated.forEach(name => {
+					names.forEach(name => {
 						if (template_scope.names.has(name)) {
 							template_scope.dependenciesForName.get(name).forEach(name => {
 								const variable = component.var_lookup.get(name);
-								if (variable) variable.mutated = true;
+								if (variable) variable[deep ? 'mutated' : 'reassigned'] = true;
 							});
 						} else {
 							component.add_reference(name);
 
 							const variable = component.var_lookup.get(name);
-							if (variable) variable.mutated = true;
+							if (variable) variable[deep ? 'mutated' : 'reassigned'] = true;
 						}
 					});
 				}
@@ -381,7 +384,7 @@ export default class Expression {
 
 						component.add_var({
 							name,
-							injected: true,
+							internal: true,
 							hoistable: true,
 							referenced: true
 						});
@@ -394,7 +397,7 @@ export default class Expression {
 
 						component.add_var({
 							name,
-							injected: true,
+							internal: true,
 							referenced: true
 						});
 					}
@@ -406,7 +409,7 @@ export default class Expression {
 
 						component.add_var({
 							name,
-							injected: true,
+							internal: true,
 							referenced: true
 						});
 

src/compile/render-dom/wrappers/AwaitBlock.ts

@@ -181,9 +181,11 @@ export default class AwaitBlockWrapper extends Wrapper {
 		}
 
 		const conditions = [];
-		if (this.node.expression.dependencies.size > 0) {
+		const dependencies = this.node.expression.dynamic_dependencies();
+
+		if (dependencies.length > 0) {
 			conditions.push(
-				`(${[...this.node.expression.dependencies].map(dep => `'${dep}' in changed`).join(' || ')})`
+				`(${dependencies.map(dep => `'${dep}' in changed`).join(' || ')})`
 			);
 		}
 

src/compile/render-dom/wrappers/Element/index.ts

@@ -408,7 +408,7 @@ export default class ElementWrapper extends Wrapper {
 
 			renderer.component.add_var({
 				name: handler,
-				injected: true,
+				internal: true,
 				referenced: true
 			});
 
@@ -513,7 +513,7 @@ export default class ElementWrapper extends Wrapper {
 
 			renderer.component.add_var({
 				name,
-				injected: true,
+				internal: true,
 				referenced: true
 			});
 

src/compile/render-dom/wrappers/InlineComponent/index.ts

@@ -147,14 +147,16 @@ export default class InlineComponentWrapper extends Wrapper {
 		}
 
 		const fragment_dependencies = new Set();
-		this.slots.forEach((slot, name) => {
+		this.slots.forEach(slot => {
 			slot.block.dependencies.forEach(name => {
 				const is_let = slot.scope.is_let(name);
 				const variable = renderer.component.var_lookup.get(name);
 
-				if (is_let || variable.mutated) {
+				if (is_let) fragment_dependencies.add(name);
-					fragment_dependencies.add(name);
+
-				}
+				if (!variable) return;
+				if (variable.mutated || variable.reassigned) fragment_dependencies.add(name);
+				if (!variable.module && variable.writable && variable.export_name) fragment_dependencies.add(name);
 			});
 		});
 
@@ -241,7 +243,7 @@ export default class InlineComponentWrapper extends Wrapper {
 
 				component.add_var({
 					name: fn,
-					injected: true,
+					internal: true,
 					referenced: true
 				});
 
@@ -276,7 +278,7 @@ export default class InlineComponentWrapper extends Wrapper {
 
 			component.add_var({
 				name,
-				injected: true,
+				internal: true,
 				referenced: true
 			});
 

src/compile/render-dom/wrappers/Window.ts

@@ -120,7 +120,7 @@ export default class WindowWrapper extends Wrapper {
 
 			component.add_var({
 				name: handler_name,
-				injected: true,
+				internal: true,
 				referenced: true
 			});
 

src/interfaces.ts

@@ -91,7 +91,8 @@ export interface Var {
 
 	// used internally, but not exposed
 	global?: boolean;
-	implicit?: boolean;
+	implicit?: boolean; // logic-less template references
+	internal?: boolean; // event handlers, bindings
 	initialised?: boolean;
 	hoistable?: boolean;
 }

test/stats/samples/mutated-vs-reassigned-bindings/_config.js

@@ -0,0 +1,26 @@
+export default {
+	test(assert, stats) {
+		assert.deepEqual(stats.vars, [
+			{
+				name: 'count',
+				export_name: null,
+				injected: false,
+				module: false,
+				mutated: false,
+				reassigned: true,
+				referenced: true,
+				writable: true
+			},
+			{
+				name: 'user',
+				export_name: null,
+				injected: false,
+				module: false,
+				mutated: true,
+				reassigned: false,
+				referenced: true,
+				writable: false
+			}
+		]);
+	}
+};

test/stats/samples/mutated-vs-reassigned-bindings/input.html

@@ -0,0 +1,7 @@
+<script>
+	let count;
+	const user = { name: 'world' };
+</script>
+
+<input bind:value={user.name}>
+<input type=number bind:value={count}>

test/stats/samples/mutated-vs-reassigned/_config.js

@@ -0,0 +1,26 @@
+export default {
+	test(assert, stats) {
+		assert.deepEqual(stats.vars, [
+			{
+				name: 'count',
+				export_name: null,
+				injected: false,
+				module: false,
+				mutated: false,
+				reassigned: true,
+				referenced: true,
+				writable: true
+			},
+			{
+				name: 'user',
+				export_name: null,
+				injected: false,
+				module: false,
+				mutated: true,
+				reassigned: false,
+				referenced: true,
+				writable: false
+			}
+		]);
+	}
+};

test/stats/samples/mutated-vs-reassigned/input.html

@@ -0,0 +1,7 @@
+<script>
+	let count;
+	const user = { name: 'world' };
+</script>
+
+<input on:input="{e => user.name = e.value}">
+<input type=number on:input="{e => count = +e.value}">

test/stats/samples/props/_config.js

@@ -6,7 +6,7 @@ export default {
 				export_name: 'name',
 				injected: false,
 				module: false,
-				mutated: true,
+				mutated: false,
 				reassigned: false,
 				referenced: true,
 				writable: true
@@ -16,7 +16,7 @@ export default {
 				export_name: 'cats',
 				injected: false,
 				module: false,
-				mutated: true,
+				mutated: false,
 				reassigned: false,
 				referenced: true,
 				writable: true
@@ -36,8 +36,8 @@ export default {
 				export_name: null,
 				injected: false,
 				module: false,
-				mutated: true,
+				mutated: false,
-				reassigned: false,
+				reassigned: true,
 				referenced: true,
 				writable: true
 			}