diff --git a/src/compiler/compile/render_dom/Block.ts b/src/compiler/compile/render_dom/Block.ts
index 311241d6cd..bbcea2a302 100644
--- a/src/compiler/compile/render_dom/Block.ts
+++ b/src/compiler/compile/render_dom/Block.ts
@@ -1,385 +1,393 @@
-import Renderer, { BindingGroup } from './Renderer';
-import Wrapper from './wrappers/shared/Wrapper';
 import { b, x } from 'code-red';
-import { Node, Identifier, ArrayPattern } from 'estree';
-import { is_head } from './wrappers/shared/is_head';
-import { regex_double_quotes } from '../../utils/patterns';
-
-export interface Bindings {
-	object: Identifier;
-	property: Identifier;
-	snippet: Node;
-	store: string;
-	modifier: (node: Node) => Node;
-}
-
-export interface BlockOptions {
-	parent?: Block;
-	name: Identifier;
-	type: string;
-	renderer?: Renderer;
-	comment?: string;
-	key?: Identifier;
-	bindings?: Map<string, Bindings>;
-	dependencies?: Set<string>;
-}
-
+import { is_head } from './wrappers/shared/is_head.js';
+import { regex_double_quotes } from '../../utils/patterns.js';
 export default class Block {
-	parent?: Block;
-	renderer: Renderer;
-	name: Identifier;
-	type: string;
-	comment?: string;
-
-	wrappers: Wrapper[];
-
-	key: Identifier;
-	first: Identifier;
-
-	dependencies: Set<string> = new Set();
-
-	bindings: Map<string, Bindings>;
-	binding_group_initialised: Set<string> = new Set();
-	binding_groups: Set<BindingGroup> = new Set();
-
-	chunks: {
-		declarations: Array<Node | Node[]>;
-		init: Array<Node | Node[]>;
-		create: Array<Node | Node[]>;
-		claim: Array<Node | Node[]>;
-		hydrate: Array<Node | Node[]>;
-		mount: Array<Node | Node[]>;
-		measure: Array<Node | Node[]>;
-		restore_measurements: Array<Node | Node[]>;
-		fix: Array<Node | Node[]>;
-		animate: Array<Node | Node[]>;
-		intro: Array<Node | Node[]>;
-		update: Array<Node | Node[]>;
-		outro: Array<Node | Node[]>;
-		destroy: Array<Node | Node[]>;
-	};
-
-	event_listeners: Node[] = [];
-
-	maintain_context: boolean;
-	has_animation: boolean;
-	has_intros: boolean;
-	has_outros: boolean;
-	has_intro_method: boolean; // could have the method without the transition, due to siblings
-	has_outro_method: boolean;
-	outros: number;
-
-	aliases: Map<string, Identifier>;
-	variables: Map<string, { id: Identifier; init?: Node }> = new Map();
-	get_unique_name: (name: string) => Identifier;
-
-	has_update_method = false;
-	autofocus?: { element_var: string; condition_expression?: any };
-
-	constructor(options: BlockOptions) {
-		this.parent = options.parent;
-		this.renderer = options.renderer;
-		this.name = options.name;
-		this.type = options.type;
-		this.comment = options.comment;
-
-		this.wrappers = [];
-
-		// for keyed each blocks
-		this.key = options.key;
-		this.first = null;
-
-		this.bindings = options.bindings;
-
-		this.chunks = {
-			declarations: [],
-			init: [],
-			create: [],
-			claim: [],
-			hydrate: [],
-			mount: [],
-			measure: [],
-			restore_measurements: [],
-			fix: [],
-			animate: [],
-			intro: [],
-			update: [],
-			outro: [],
-			destroy: []
-		};
-
-		this.has_animation = false;
-		this.has_intro_method = false; // a block could have an intro method but not intro transitions, e.g. if a sibling block has intros
-		this.has_outro_method = false;
-		this.outros = 0;
-
-		this.get_unique_name = this.renderer.component.get_unique_name_maker();
-
-		this.aliases = new Map();
-		if (this.key) this.aliases.set('key', this.get_unique_name('key'));
-	}
-
-	assign_variable_names() {
-		const seen: Set<string> = new Set();
-		const dupes: Set<string> = new Set();
-
-		let i = this.wrappers.length;
-
-		while (i--) {
-			const wrapper = this.wrappers[i];
-
-			if (!wrapper.var) continue;
-
-			if (seen.has(wrapper.var.name)) {
-				dupes.add(wrapper.var.name);
-			}
-
-			seen.add(wrapper.var.name);
-		}
-
-		const counts = new Map();
-		i = this.wrappers.length;
-
-		while (i--) {
-			const wrapper = this.wrappers[i];
-
-			if (!wrapper.var) continue;
-
-			let suffix = '';
-			if (dupes.has(wrapper.var.name)) {
-				const i = counts.get(wrapper.var.name) || 0;
-				counts.set(wrapper.var.name, i + 1);
-				suffix = i;
-			}
-			wrapper.var.name = this.get_unique_name(wrapper.var.name + suffix).name;
-		}
-	}
-
-	add_dependencies(dependencies: Set<string>) {
-		dependencies.forEach((dependency) => {
-			this.dependencies.add(dependency);
-		});
-
-		this.has_update_method = true;
-		if (this.parent) {
-			this.parent.add_dependencies(dependencies);
-		}
-	}
-
-	add_element(
-		id: Identifier,
-		render_statement: Node,
-		claim_statement: Node,
-		parent_node: Node,
-		no_detach?: boolean
-	) {
-		this.add_variable(id);
-		this.chunks.create.push(b`${id} = ${render_statement};`);
-
-		if (this.renderer.options.hydratable) {
-			this.chunks.claim.push(b`${id} = ${claim_statement || render_statement};`);
-		}
-
-		if (parent_node) {
-			this.chunks.mount.push(b`@append(${parent_node}, ${id});`);
-			if (is_head(parent_node) && !no_detach) this.chunks.destroy.push(b`@detach(${id});`);
-		} else {
-			this.chunks.mount.push(b`@insert(#target, ${id}, #anchor);`);
-			if (!no_detach) this.chunks.destroy.push(b`if (detaching) @detach(${id});`);
-		}
-	}
-
-	add_intro(local?: boolean) {
-		this.has_intros = this.has_intro_method = true;
-		if (!local && this.parent) this.parent.add_intro();
-	}
-
-	add_outro(local?: boolean) {
-		this.has_outros = this.has_outro_method = true;
-		this.outros += 1;
-		if (!local && this.parent) this.parent.add_outro();
-	}
-
-	add_animation() {
-		this.has_animation = true;
-	}
-
-	add_variable(id: Identifier, init?: Node) {
-		if (this.variables.has(id.name)) {
-			throw new Error(`Variable '${id.name}' already initialised with a different value`);
-		}
-
-		this.variables.set(id.name, { id, init });
-	}
-
-	alias(name: string) {
-		if (!this.aliases.has(name)) {
-			this.aliases.set(name, this.get_unique_name(name));
-		}
-
-		return this.aliases.get(name);
-	}
-
-	child(options: BlockOptions) {
-		return new Block(Object.assign({}, this, { key: null }, options, { parent: this }));
-	}
-
-	get_contents(key?: any) {
-		const { dev } = this.renderer.options;
-
-		if (this.has_outros) {
-			this.add_variable({ type: 'Identifier', name: '#current' });
-
-			if (this.chunks.intro.length > 0) {
-				this.chunks.intro.push(b`#current = true;`);
-				this.chunks.mount.push(b`#current = true;`);
-			}
-
-			if (this.chunks.outro.length > 0) {
-				this.chunks.outro.push(b`#current = false;`);
-			}
-		}
-
-		if (this.autofocus) {
-			if (this.autofocus.condition_expression) {
-				this.chunks.mount.push(
-					b`if (${this.autofocus.condition_expression}) ${this.autofocus.element_var}.focus();`
-				);
-			} else {
-				this.chunks.mount.push(b`${this.autofocus.element_var}.focus();`);
-			}
-		}
-
-		this.render_binding_groups();
-		this.render_listeners();
-
-		const properties: Record<string, any> = {};
-
-		const noop = x`@noop`;
-
-		properties.key = key;
-
-		if (this.first) {
-			properties.first = x`null`;
-			this.chunks.hydrate.push(b`this.first = ${this.first};`);
-		}
-
-		if (this.chunks.create.length === 0 && this.chunks.hydrate.length === 0) {
-			properties.create = noop;
-		} else {
-			const hydrate =
-				this.chunks.hydrate.length > 0 &&
-				(this.renderer.options.hydratable ? b`this.h();` : this.chunks.hydrate);
-
-			properties.create = x`function #create() {
+
+    /** @type {Block} */
+    parent;
+
+    /** @type {import('./Renderer.js').default} */
+    renderer;
+
+    /** @type {import('estree').Identifier} */
+    name;
+
+    /** @type {string} */
+    type;
+
+    /** @type {string} */
+    comment;
+
+    /** @type {import('./wrappers/shared/Wrapper.js').default[]} */
+    wrappers;
+
+    /** @type {import('estree').Identifier} */
+    key;
+
+    /** @type {import('estree').Identifier} */
+    first;
+
+    /** @type {Set<string>} */
+    dependencies = new Set();
+
+    /** @type {Map<string, Bindings>} */
+    bindings;
+
+    /** @type {Set<string>} */
+    binding_group_initialised = new Set();
+
+    /** @type {Set<import('./Renderer.js').BindingGroup>} */
+    binding_groups = new Set();
+    /**
+     * @type {{
+     * 		declarations: Array<import('estree').Node | import('estree').Node[]>;
+     * 		init: Array<import('estree').Node | import('estree').Node[]>;
+     * 		create: Array<import('estree').Node | import('estree').Node[]>;
+     * 		claim: Array<import('estree').Node | import('estree').Node[]>;
+     * 		hydrate: Array<import('estree').Node | import('estree').Node[]>;
+     * 		mount: Array<import('estree').Node | import('estree').Node[]>;
+     * 		measure: Array<import('estree').Node | import('estree').Node[]>;
+     * 		restore_measurements: Array<import('estree').Node | import('estree').Node[]>;
+     * 		fix: Array<import('estree').Node | import('estree').Node[]>;
+     * 		animate: Array<import('estree').Node | import('estree').Node[]>;
+     * 		intro: Array<import('estree').Node | import('estree').Node[]>;
+     * 		update: Array<import('estree').Node | import('estree').Node[]>;
+     * 		outro: Array<import('estree').Node | import('estree').Node[]>;
+     * 		destroy: Array<import('estree').Node | import('estree').Node[]>;
+     * 	}}
+     */
+    chunks;
+
+    /** @type {import('estree').Node[]} */
+    event_listeners = [];
+
+    /** @type {boolean} */
+    maintain_context;
+
+    /** @type {boolean} */
+    has_animation;
+
+    /** @type {boolean} */
+    has_intros;
+
+    /** @type {boolean} */
+    has_outros;
+
+    /** @type {boolean} */
+    has_intro_method; // could have the method without the transition, due to siblings
+
+    /** @type {boolean} */
+    has_outro_method;
+
+    /** @type {number} */
+    outros;
+
+    /** @type {Map<string, import('estree').Identifier>} */
+    aliases;
+
+    /** @type {Map<string, { id: import('estree').Identifier; init?: import('estree').Node }>} */
+    variables = new Map();
+
+    /** @type {(name: string) => import('estree').Identifier} */
+    get_unique_name;
+    /** */
+    has_update_method = false;
+
+    /** @type {{ element_var: string; condition_expression?: any }} */
+    autofocus;
+
+    /** @param {BlockOptions} options */
+    constructor(options) {
+        this.parent = options.parent;
+        this.renderer = options.renderer;
+        this.name = options.name;
+        this.type = options.type;
+        this.comment = options.comment;
+        this.wrappers = [];
+        // for keyed each blocks
+        this.key = options.key;
+        this.first = null;
+        this.bindings = options.bindings;
+        this.chunks = {
+            declarations: [],
+            init: [],
+            create: [],
+            claim: [],
+            hydrate: [],
+            mount: [],
+            measure: [],
+            restore_measurements: [],
+            fix: [],
+            animate: [],
+            intro: [],
+            update: [],
+            outro: [],
+            destroy: []
+        };
+        this.has_animation = false;
+        this.has_intro_method = false; // a block could have an intro method but not intro transitions, e.g. if a sibling block has intros
+        this.has_outro_method = false;
+        this.outros = 0;
+        this.get_unique_name = this.renderer.component.get_unique_name_maker();
+        this.aliases = new Map();
+        if (this.key)
+            this.aliases.set('key', this.get_unique_name('key'));
+    }
+    assign_variable_names() {
+
+        /** @type {Set<string>} */
+        const seen = new Set();
+
+        /** @type {Set<string>} */
+        const dupes = new Set();
+        let i = this.wrappers.length;
+        while (i--) {
+            const wrapper = this.wrappers[i];
+            if (!wrapper.var)
+                continue;
+            if (seen.has(wrapper.var.name)) {
+                dupes.add(wrapper.var.name);
+            }
+            seen.add(wrapper.var.name);
+        }
+        const counts = new Map();
+        i = this.wrappers.length;
+        while (i--) {
+            const wrapper = this.wrappers[i];
+            if (!wrapper.var)
+                continue;
+            let suffix = '';
+            if (dupes.has(wrapper.var.name)) {
+                const i = counts.get(wrapper.var.name) || 0;
+                counts.set(wrapper.var.name, i + 1);
+                suffix = i;
+            }
+            wrapper.var.name = this.get_unique_name(wrapper.var.name + suffix).name;
+        }
+    }
+
+    /** @param {Set<string>} dependencies */
+    add_dependencies(dependencies) {
+        dependencies.forEach((dependency) => {
+            this.dependencies.add(dependency);
+        });
+        this.has_update_method = true;
+        if (this.parent) {
+            this.parent.add_dependencies(dependencies);
+        }
+    }
+
+ /**
+  * @param {import('estree').Identifier} id
+     * @param {import('estree').Node} render_statement
+     * @param {import('estree').Node} claim_statement
+     * @param {import('estree').Node} parent_node
+     * @param {boolean} [no_detach]
+     */
+    add_element(id, render_statement, claim_statement, parent_node, no_detach) {
+        this.add_variable(id);
+        this.chunks.create.push(b `${id} = ${render_statement};`);
+        if (this.renderer.options.hydratable) {
+            this.chunks.claim.push(b `${id} = ${claim_statement || render_statement};`);
+        }
+        if (parent_node) {
+            this.chunks.mount.push(b `@append(${parent_node}, ${id});`);
+            if (is_head(parent_node) && !no_detach)
+                this.chunks.destroy.push(b `@detach(${id});`);
+        }
+        else {
+            this.chunks.mount.push(b `@insert(#target, ${id}, #anchor);`);
+            if (!no_detach)
+                this.chunks.destroy.push(b `if (detaching) @detach(${id});`);
+        }
+    }
+
+    /** @param {boolean} [local] */
+    add_intro(local) {
+        this.has_intros = this.has_intro_method = true;
+        if (!local && this.parent)
+            this.parent.add_intro();
+    }
+
+    /** @param {boolean} [local] */
+    add_outro(local) {
+        this.has_outros = this.has_outro_method = true;
+        this.outros += 1;
+        if (!local && this.parent)
+            this.parent.add_outro();
+    }
+    add_animation() {
+        this.has_animation = true;
+    }
+
+ /**
+  * @param {import('estree').Identifier} id
+     * @param {import('estree').Node} [init]
+     */
+    add_variable(id, init) {
+        if (this.variables.has(id.name)) {
+            throw new Error(`Variable '${id.name}' already initialised with a different value`);
+        }
+        this.variables.set(id.name, { id, init });
+    }
+
+    /** @param {string} name */
+    alias(name) {
+        if (!this.aliases.has(name)) {
+            this.aliases.set(name, this.get_unique_name(name));
+        }
+        return this.aliases.get(name);
+    }
+
+    /** @param {BlockOptions} options */
+    child(options) {
+        return new Block(Object.assign({}, this, { key: null }, options, { parent: this }));
+    }
+
+    /** @param {any} [key] */
+    get_contents(key) {
+        const { dev } = this.renderer.options;
+        if (this.has_outros) {
+            this.add_variable({ type: 'Identifier', name: '#current' });
+            if (this.chunks.intro.length > 0) {
+                this.chunks.intro.push(b `#current = true;`);
+                this.chunks.mount.push(b `#current = true;`);
+            }
+            if (this.chunks.outro.length > 0) {
+                this.chunks.outro.push(b `#current = false;`);
+            }
+        }
+        if (this.autofocus) {
+            if (this.autofocus.condition_expression) {
+                this.chunks.mount.push(b `if (${this.autofocus.condition_expression}) ${this.autofocus.element_var}.focus();`);
+            }
+            else {
+                this.chunks.mount.push(b `${this.autofocus.element_var}.focus();`);
+            }
+        }
+        this.render_binding_groups();
+        this.render_listeners();
+
+        /** @type {Record<string, any>} */
+        const properties = {};
+        const noop = x `@noop`;
+        properties.key = key;
+        if (this.first) {
+            properties.first = x `null`;
+            this.chunks.hydrate.push(b `this.first = ${this.first};`);
+        }
+        if (this.chunks.create.length === 0 && this.chunks.hydrate.length === 0) {
+            properties.create = noop;
+        }
+        else {
+            const hydrate = this.chunks.hydrate.length > 0 &&
+                (this.renderer.options.hydratable ? b `this.h();` : this.chunks.hydrate);
+            properties.create = x `function #create() {
 				${this.chunks.create}
 				${hydrate}
 			}`;
-		}
-
-		if (this.renderer.options.hydratable || this.chunks.claim.length > 0) {
-			if (this.chunks.claim.length === 0 && this.chunks.hydrate.length === 0) {
-				properties.claim = noop;
-			} else {
-				properties.claim = x`function #claim(#nodes) {
+        }
+        if (this.renderer.options.hydratable || this.chunks.claim.length > 0) {
+            if (this.chunks.claim.length === 0 && this.chunks.hydrate.length === 0) {
+                properties.claim = noop;
+            }
+            else {
+                properties.claim = x `function #claim(#nodes) {
 					${this.chunks.claim}
-					${this.renderer.options.hydratable && this.chunks.hydrate.length > 0 && b`this.h();`}
+					${this.renderer.options.hydratable && this.chunks.hydrate.length > 0 && b `this.h();`}
 				}`;
-			}
-		}
-
-		if (this.renderer.options.hydratable && this.chunks.hydrate.length > 0) {
-			properties.hydrate = x`function #hydrate() {
+            }
+        }
+        if (this.renderer.options.hydratable && this.chunks.hydrate.length > 0) {
+            properties.hydrate = x `function #hydrate() {
 				${this.chunks.hydrate}
 			}`;
-		}
-
-		if (this.chunks.mount.length === 0) {
-			properties.mount = noop;
-		} else if (this.event_listeners.length === 0) {
-			properties.mount = x`function #mount(#target, #anchor) {
+        }
+        if (this.chunks.mount.length === 0) {
+            properties.mount = noop;
+        }
+        else if (this.event_listeners.length === 0) {
+            properties.mount = x `function #mount(#target, #anchor) {
 				${this.chunks.mount}
 			}`;
-		} else {
-			properties.mount = x`function #mount(#target, #anchor) {
+        }
+        else {
+            properties.mount = x `function #mount(#target, #anchor) {
 				${this.chunks.mount}
 			}`;
-		}
-
-		if (this.has_update_method || this.maintain_context) {
-			if (this.chunks.update.length === 0 && !this.maintain_context) {
-				properties.update = noop;
-			} else {
-				const ctx = this.maintain_context ? x`#new_ctx` : x`#ctx`;
-
-				let dirty: Identifier | ArrayPattern = { type: 'Identifier', name: '#dirty' };
-				if (!this.renderer.context_overflow && !this.parent) {
-					dirty = { type: 'ArrayPattern', elements: [dirty] };
-				}
-
-				properties.update = x`function #update(${ctx}, ${dirty}) {
-					${this.maintain_context && b`#ctx = ${ctx};`}
+        }
+        if (this.has_update_method || this.maintain_context) {
+            if (this.chunks.update.length === 0 && !this.maintain_context) {
+                properties.update = noop;
+            }
+            else {
+                const ctx = this.maintain_context ? x `#new_ctx` : x `#ctx`;
+
+                /** @type {import('estree').Identifier | import('estree').ArrayPattern} */
+                let dirty = { type: 'Identifier', name: '#dirty' };
+                if (!this.renderer.context_overflow && !this.parent) {
+                    dirty = { type: 'ArrayPattern', elements: [dirty] };
+                }
+                properties.update = x `function #update(${ctx}, ${dirty}) {
+					${this.maintain_context && b `#ctx = ${ctx};`}
 					${this.chunks.update}
 				}`;
-			}
-		}
-
-		if (this.has_animation) {
-			properties.measure = x`function #measure() {
+            }
+        }
+        if (this.has_animation) {
+            properties.measure = x `function #measure() {
 				${this.chunks.measure}
 			}`;
-
-			if (this.chunks.restore_measurements.length) {
-				properties.restore_measurements = x`function #restore_measurements(#measurement) {
+            if (this.chunks.restore_measurements.length) {
+                properties.restore_measurements = x `function #restore_measurements(#measurement) {
 					${this.chunks.restore_measurements}
 				}`;
-			}
-
-			properties.fix = x`function #fix() {
+            }
+            properties.fix = x `function #fix() {
 				${this.chunks.fix}
 			}`;
-
-			properties.animate = x`function #animate() {
+            properties.animate = x `function #animate() {
 				${this.chunks.animate}
 			}`;
-		}
-
-		if (this.has_intro_method || this.has_outro_method) {
-			if (this.chunks.intro.length === 0) {
-				properties.intro = noop;
-			} else {
-				properties.intro = x`function #intro(#local) {
-					${this.has_outros && b`if (#current) return;`}
+        }
+        if (this.has_intro_method || this.has_outro_method) {
+            if (this.chunks.intro.length === 0) {
+                properties.intro = noop;
+            }
+            else {
+                properties.intro = x `function #intro(#local) {
+					${this.has_outros && b `if (#current) return;`}
 					${this.chunks.intro}
 				}`;
-			}
-
-			if (this.chunks.outro.length === 0) {
-				properties.outro = noop;
-			} else {
-				properties.outro = x`function #outro(#local) {
+            }
+            if (this.chunks.outro.length === 0) {
+                properties.outro = noop;
+            }
+            else {
+                properties.outro = x `function #outro(#local) {
 					${this.chunks.outro}
 				}`;
-			}
-		}
-
-		if (this.chunks.destroy.length === 0) {
-			properties.destroy = noop;
-		} else {
-			properties.destroy = x`function #destroy(detaching) {
+            }
+        }
+        if (this.chunks.destroy.length === 0) {
+            properties.destroy = noop;
+        }
+        else {
+            properties.destroy = x `function #destroy(detaching) {
 				${this.chunks.destroy}
 			}`;
-		}
-
-		if (!this.renderer.component.compile_options.dev) {
-			// allow shorthand names
-			for (const name in properties) {
-				const property = properties[name];
-				if (property) property.id = null;
-			}
-		}
-
-		const return_value: any = x`{
+        }
+        if (!this.renderer.component.compile_options.dev) {
+            // allow shorthand names
+            for (const name in properties) {
+                const property = properties[name];
+                if (property)
+                    property.id = null;
+            }
+        }
+
+        /** @type {any} */
+        const return_value = x `{
 			key: ${properties.key},
 			first: ${properties.first},
 			c: ${properties.create},
@@ -395,21 +403,18 @@ export default class Block {
 			o: ${properties.outro},
 			d: ${properties.destroy}
 		}`;
-
-		const block = dev && this.get_unique_name('block');
-
-		const body = b`
+        const block = dev && this.get_unique_name('block');
+        const body = b `
 			${this.chunks.declarations}
 
 			${Array.from(this.variables.values()).map(({ id, init }) => {
-				return init ? b`let ${id} = ${init}` : b`let ${id}`;
-			})}
+            return init ? b `let ${id} = ${init}` : b `let ${id}`;
+        })}
 
 			${this.chunks.init}
 
-			${
-				dev
-					? b`
+			${dev
+            ? b `
 					const ${block} = ${return_value};
 					@dispatch_dev("SvelteRegisterBlock", {
 						block: ${block},
@@ -419,72 +424,66 @@ export default class Block {
 						ctx: #ctx
 					});
 					return ${block};`
-					: b`
-					return ${return_value};`
-			}
+            : b `
+					return ${return_value};`}
 		`;
-
-		return body;
-	}
-
-	has_content(): boolean {
-		return (
-			!!this.first ||
-			this.event_listeners.length > 0 ||
-			this.chunks.intro.length > 0 ||
-			this.chunks.outro.length > 0 ||
-			this.chunks.create.length > 0 ||
-			this.chunks.hydrate.length > 0 ||
-			this.chunks.claim.length > 0 ||
-			this.chunks.mount.length > 0 ||
-			this.chunks.update.length > 0 ||
-			this.chunks.destroy.length > 0 ||
-			this.has_animation
-		);
-	}
-
-	render() {
-		const key = this.key && this.get_unique_name('key');
-
-		const args: any[] = [x`#ctx`];
-		if (key) args.unshift(key);
-
-		const fn = b`function ${this.name}(${args}) {
+        return body;
+    }
+
+    /** @returns {boolean} */
+    has_content() {
+        return (!!this.first ||
+            this.event_listeners.length > 0 ||
+            this.chunks.intro.length > 0 ||
+            this.chunks.outro.length > 0 ||
+            this.chunks.create.length > 0 ||
+            this.chunks.hydrate.length > 0 ||
+            this.chunks.claim.length > 0 ||
+            this.chunks.mount.length > 0 ||
+            this.chunks.update.length > 0 ||
+            this.chunks.destroy.length > 0 ||
+            this.has_animation);
+    }
+    render() {
+        const key = this.key && this.get_unique_name('key');
+
+        /** @type {any[]} */
+        const args = [x `#ctx`];
+        if (key)
+            args.unshift(key);
+        const fn = b `function ${this.name}(${args}) {
 			${this.get_contents(key)}
 		}`;
-
-		return this.comment
-			? b`
+        return this.comment
+            ? b `
 				// ${this.comment}
 				${fn}`
-			: fn;
-	}
-
-	render_listeners(chunk: string = '') {
-		if (this.event_listeners.length > 0) {
-			this.add_variable({ type: 'Identifier', name: '#mounted' });
-			this.chunks.destroy.push(b`#mounted = false`);
-
-			const dispose: Identifier = {
-				type: 'Identifier',
-				name: `#dispose${chunk}`
-			};
-
-			this.add_variable(dispose);
-
-			if (this.event_listeners.length === 1) {
-				this.chunks.mount.push(
-					b`
+            : fn;
+    }
+
+    /** @param {string} chunk */
+    render_listeners(chunk = '') {
+        if (this.event_listeners.length > 0) {
+            this.add_variable({ type: 'Identifier', name: '#mounted' });
+            this.chunks.destroy.push(b `#mounted = false`);
+
+            /** @type {import('estree').Identifier} */
+            const dispose = {
+                type: 'Identifier',
+                name: `#dispose${chunk}`
+            };
+            this.add_variable(dispose);
+            if (this.event_listeners.length === 1) {
+                this.chunks.mount.push(b `
 						if (!#mounted) {
 							${dispose} = ${this.event_listeners[0]};
 							#mounted = true;
 						}
-					`
-				);
-
-				this.chunks.destroy.push(b`${dispose}();`);
-			} else {
-				this.chunks.mount.push(b`
+					`);
+                this.chunks.destroy.push(b `${dispose}();`);
+            }
+            else {
+                this.chunks.mount.push(b `
 					if (!#mounted) {
 						${dispose} = [
 							${this.event_listeners}
@@ -492,15 +491,34 @@ export default class Block {
 						#mounted = true;
 					}
 				`);
+                this.chunks.destroy.push(b `@run_all(${dispose});`);
+            }
+        }
+    }
+    render_binding_groups() {
+        for (const binding_group of this.binding_groups) {
+            binding_group.render(this);
+        }
+    }
+}
 
-				this.chunks.destroy.push(b`@run_all(${dispose});`);
-			}
-		}
-	}
 
-	render_binding_groups() {
-		for (const binding_group of this.binding_groups) {
-			binding_group.render(this);
-		}
-	}
-}
+
+
+/** @typedef {Object} Bindings
+ * @property {Identifier} object
+ * @property {Identifier} property
+ * @property {Node} snippet
+ * @property {string} store
+ * @property {(node:Node)=>Node} modifier 
+ */
+/** @typedef {Object} BlockOptions
+ * @property {Block} [parent]
+ * @property {Identifier} name
+ * @property {string} type
+ * @property {Renderer} [renderer]
+ * @property {string} [comment]
+ * @property {Identifier} [key]
+ * @property {Map<string,Bindings>} [bindings]
+ * @property {Set<string>} [dependencies] 
+ */
\ No newline at end of file
diff --git a/src/compiler/compile/render_dom/wrappers/Window.js b/src/compiler/compile/render_dom/wrappers/Window.js
index 1a1553c07b..0dd8b24332 100644
--- a/src/compiler/compile/render_dom/wrappers/Window.js
+++ b/src/compiler/compile/render_dom/wrappers/Window.js
@@ -3,6 +3,7 @@ import { b, x } from 'code-red';
 import add_event_handlers from './shared/add_event_handlers.js';
 import add_actions from './shared/add_actions.js';
 import EventHandler from './Element/EventHandler.js';
+
 const associated_events = {
 	innerWidth: 'resize',
 	innerHeight: 'resize',