diff --git a/src/compiler/compile/render_dom/Renderer.ts b/src/compiler/compile/render_dom/Renderer.ts
index 179fc0c956..c00ef95586 100644
--- a/src/compiler/compile/render_dom/Renderer.ts
+++ b/src/compiler/compile/render_dom/Renderer.ts
@@ -168,7 +168,7 @@ export default class Renderer {
 		return member;
 	}
 
-	invalidate(name: string, value?, main_execution_context: boolean = false) {
+	invalidate(name: string, value?: unknown, main_execution_context: boolean = false) {
 		return renderer_invalidate(this, name, value, main_execution_context);
 	}
 
diff --git a/src/compiler/compile/render_dom/index.ts b/src/compiler/compile/render_dom/index.ts
index c36ca2acd4..3055715b4c 100644
--- a/src/compiler/compile/render_dom/index.ts
+++ b/src/compiler/compile/render_dom/index.ts
@@ -83,7 +83,7 @@ export default function dom(
 	}
 
 	const uses_slots = component.var_lookup.has('$$slots');
-	let compute_slots;
+	let compute_slots: Node[] | undefined;
 	if (uses_slots) {
 		compute_slots = b`
 			const $$slots = @compute_slots(#slots);
@@ -396,7 +396,7 @@ export default function dom(
 
 	if (has_definition) {
 		const reactive_declarations: (Node | Node[]) = [];
-		const fixed_reactive_declarations = []; // not really 'reactive' but whatever
+		const fixed_reactive_declarations: Node[] = []; // not really 'reactive' but whatever
 
 		component.reactive_declarations.forEach(d => {
 			const dependencies = Array.from(d.dependencies);
@@ -441,7 +441,7 @@ export default function dom(
 			return b`let ${$name};`;
 		});
 
-		let unknown_props_check;
+		let unknown_props_check: Node[] | undefined;
 		if (component.compile_options.dev && !(uses_props || uses_rest)) {
 			unknown_props_check = b`
 				const writable_props = [${writable_props.map(prop => x`'${prop.export_name}'`)}];
diff --git a/src/compiler/compile/render_dom/invalidate.ts b/src/compiler/compile/render_dom/invalidate.ts
index 7eeb34a894..ffc5b6b42e 100644
--- a/src/compiler/compile/render_dom/invalidate.ts
+++ b/src/compiler/compile/render_dom/invalidate.ts
@@ -80,7 +80,7 @@ export function invalidate(renderer: Renderer, scope: Scope, node: Node, names:
 	return invalidate;
 }
 
-export function renderer_invalidate(renderer: Renderer, name: string, value?, main_execution_context: boolean = false) {
+export function renderer_invalidate(renderer: Renderer, name: string, value?: unknown, main_execution_context: boolean = false) {
 	const variable = renderer.component.var_lookup.get(name);
 
 	if (variable && (variable.subscribable && (variable.reassigned || variable.export_name))) {
diff --git a/src/compiler/compile/render_dom/wrappers/EachBlock.ts b/src/compiler/compile/render_dom/wrappers/EachBlock.ts
index d4648954ca..0c49c38028 100644
--- a/src/compiler/compile/render_dom/wrappers/EachBlock.ts
+++ b/src/compiler/compile/render_dom/wrappers/EachBlock.ts
@@ -582,7 +582,7 @@ export default class EachBlockWrapper extends Wrapper {
 
 			const start = this.block.has_update_method ? 0 : '#old_length';
 
-			let remove_old_blocks;
+			let remove_old_blocks: Node[];
 
 			if (this.block.has_outros) {
 				const out = block.get_unique_name('out');
diff --git a/src/compiler/compile/render_dom/wrappers/Element/Attribute.ts b/src/compiler/compile/render_dom/wrappers/Element/Attribute.ts
index fb604f564e..81a1898331 100644
--- a/src/compiler/compile/render_dom/wrappers/Element/Attribute.ts
+++ b/src/compiler/compile/render_dom/wrappers/Element/Attribute.ts
@@ -130,7 +130,7 @@ export default class AttributeWrapper extends BaseAttributeWrapper {
 		const dependencies = this.get_dependencies();
 		const value = this.get_value(block);
 
-		let updater;
+		let updater: Node[];
 		const init = this.get_init(block, value);
 
 		if (is_legacy_input_type) {
@@ -258,7 +258,7 @@ export default class AttributeWrapper extends BaseAttributeWrapper {
 		return metadata;
 	}
 
-	get_value(block) {
+	get_value(block: Block) {
 		if (this.node.is_true) {
 			if (this.metadata && boolean_attributes.has(this.metadata.property_name.toLowerCase())) {
 				return x`true`;
@@ -287,7 +287,7 @@ export default class AttributeWrapper extends BaseAttributeWrapper {
 		return value;
 	}
 
-	get_class_name_text(block) {
+	get_class_name_text(block: Block) {
 		const scoped_css = this.node.chunks.some((chunk: Text) => chunk.synthetic);
 		const rendered = this.render_chunks(block);
 
diff --git a/src/compiler/compile/render_dom/wrappers/Element/Binding.ts b/src/compiler/compile/render_dom/wrappers/Element/Binding.ts
index bc218a510b..9e2ec85f0f 100644
--- a/src/compiler/compile/render_dom/wrappers/Element/Binding.ts
+++ b/src/compiler/compile/render_dom/wrappers/Element/Binding.ts
@@ -299,8 +299,8 @@ function get_binding_group(renderer: Renderer, value: Binding, block: Block) {
 
 	for (const dep of contextual_dependencies) {
 		const context = block.bindings.get(dep);
-		let key;
-		let name;
+		let key: string;
+		let name: string;
 		if (context) {
 			key = context.object.name;
 			name = context.property.name;
@@ -364,7 +364,7 @@ function get_event_handler(
 	const contextual_dependencies = new Set<string>(binding.node.expression.contextual_dependencies);
 
 	const context = block.bindings.get(name);
-	let set_store;
+	let set_store: Node[] | undefined;
 
 	if (context) {
 		const { object, property, store, snippet } = context;
diff --git a/src/compiler/compile/render_dom/wrappers/Element/EventHandler.ts b/src/compiler/compile/render_dom/wrappers/Element/EventHandler.ts
index fc65a9aa5e..b0ed4a73d6 100644
--- a/src/compiler/compile/render_dom/wrappers/Element/EventHandler.ts
+++ b/src/compiler/compile/render_dom/wrappers/Element/EventHandler.ts
@@ -26,7 +26,7 @@ export default class EventHandlerWrapper {
 		}
 	}
 
-	get_snippet(block) {
+	get_snippet(block: Block) {
 		const snippet = this.node.expression ? this.node.expression.manipulate(block) : block.renderer.reference(this.node.handler_name);
 
 		if (this.node.reassigned) {
diff --git a/src/compiler/compile/render_dom/wrappers/Element/fix_attribute_casing.ts b/src/compiler/compile/render_dom/wrappers/Element/fix_attribute_casing.ts
index 7044d5d7b3..0ff7c27e4b 100644
--- a/src/compiler/compile/render_dom/wrappers/Element/fix_attribute_casing.ts
+++ b/src/compiler/compile/render_dom/wrappers/Element/fix_attribute_casing.ts
@@ -6,7 +6,7 @@ svg_attributes.forEach(name => {
 	svg_attribute_lookup.set(name.toLowerCase(), name);
 });
 
-export default function fix_attribute_casing(name) {
+export default function fix_attribute_casing(name: string) {
 	name = name.toLowerCase();
 	return svg_attribute_lookup.get(name) || name;
 }
diff --git a/src/compiler/compile/render_dom/wrappers/Element/index.ts b/src/compiler/compile/render_dom/wrappers/Element/index.ts
index 01f03b5589..97984748c3 100644
--- a/src/compiler/compile/render_dom/wrappers/Element/index.ts
+++ b/src/compiler/compile/render_dom/wrappers/Element/index.ts
@@ -19,7 +19,7 @@ import { add_event_handler } from '../shared/add_event_handlers';
 import { add_action } from '../shared/add_actions';
 import bind_this from '../shared/bind_this';
 import { is_head } from '../shared/is_head';
-import { Identifier, ExpressionStatement, CallExpression } from 'estree';
+import { Identifier, ExpressionStatement, CallExpression, Node } from 'estree';
 import EventHandler from './EventHandler';
 import { extract_names } from 'periscopic';
 import Action from '../../../nodes/Action';
@@ -534,7 +534,7 @@ export default class ElementWrapper extends Wrapper {
 			.filter((attr) => !(attr instanceof SpreadAttributeWrapper) && !attr.property_name)
 			.map((attr) => p`${(attr as StyleAttributeWrapper | AttributeWrapper).name}: true`);
 
-		let reference;
+		let reference: string | ReturnType<typeof x>;
 		if (this.node.tag_expr.node.type === 'Literal') {
 			if (this.node.namespace) {
 				reference = `"${this.node.tag_expr.node.value}"`;
@@ -634,7 +634,7 @@ export default class ElementWrapper extends Wrapper {
 		// media bindings — awkward special case. The native timeupdate events
 		// fire too infrequently, so we need to take matters into our
 		// own hands
-		let animation_frame;
+		let animation_frame: Identifier | undefined;
 		if (binding_group.events[0] === 'timeupdate') {
 			animation_frame = block.get_unique_name(`${this.var.name}_animationframe`);
 			block.add_variable(animation_frame);
@@ -874,9 +874,7 @@ export default class ElementWrapper extends Wrapper {
 		}
 	}
 
-	add_transitions(
-		block: Block
-	) {
+	add_transitions(block: Block) {
 		const { intro, outro } = this.node;
 		if (!intro && !outro) return;
 
@@ -933,7 +931,7 @@ export default class ElementWrapper extends Wrapper {
 
 				const fn = this.renderer.reference(intro.name);
 
-				let intro_block;
+				let intro_block: Node[];
 
 				if (outro) {
 					intro_block = b`
@@ -1032,7 +1030,7 @@ export default class ElementWrapper extends Wrapper {
 			${outro && b`@add_transform(${this.var}, ${rect});`}
 		`);
 
-		let params;
+		let params: Node | ReturnType<typeof x>;
 		if (this.node.animation.expression) {
 			params = this.node.animation.expression.manipulate(block);
 
@@ -1060,8 +1058,8 @@ export default class ElementWrapper extends Wrapper {
 		const has_spread = this.node.attributes.some(attr => attr.is_spread);
 		this.node.classes.forEach(class_directive => {
 			const { expression, name } = class_directive;
-			let snippet;
-			let dependencies;
+			let snippet: Node | string;
+			let dependencies: Set<string>;
 			if (expression) {
 				snippet = expression.manipulate(block);
 				dependencies = expression.dependencies;
@@ -1105,7 +1103,7 @@ export default class ElementWrapper extends Wrapper {
 			const { name, expression, should_cache } = style_directive;
 
 			const snippet = expression.manipulate(block);
-			let cached_snippet;
+			let cached_snippet: Identifier | undefined;
 			if (should_cache) {
 				cached_snippet = block.get_unique_name(`style_${name.replace(regex_minus_signs, '_')}`);
 				block.add_variable(cached_snippet, snippet);
@@ -1136,7 +1134,7 @@ export default class ElementWrapper extends Wrapper {
 		});
 	}
 
-	add_manual_style_scoping(block) {
+	add_manual_style_scoping(block: Block) {
 		if (this.node.needs_manual_style_scoping) {
 			const updater = b`@toggle_class(${this.var}, "${this.node.component.stylesheet.id}", true);`;
 			block.chunks.hydrate.push(updater);
@@ -1151,7 +1149,7 @@ const regex_dollar_signs = /\$/g;
 function to_html(wrappers: Array<ElementWrapper | TextWrapper | MustacheTagWrapper | RawMustacheTagWrapper>, block: Block, literal: any, state: any, can_use_raw_text?: boolean) {
 	wrappers.forEach(wrapper => {
 		if (wrapper instanceof TextWrapper) {
-			// Don't add the <pre>/<textare> newline logic here because pre/textarea.innerHTML
+			// Don't add the <pre>/<textarea> newline logic here because pre/textarea.innerHTML
 			// would keep the leading newline, too, only someParent.innerHTML = '..<pre/textarea>..' won't
 
 			if ((wrapper as TextWrapper).use_space()) state.quasi.value.raw += ' ';
diff --git a/src/compiler/compile/render_dom/wrappers/Fragment.ts b/src/compiler/compile/render_dom/wrappers/Fragment.ts
index 1e3b89e97f..e2eb519393 100644
--- a/src/compiler/compile/render_dom/wrappers/Fragment.ts
+++ b/src/compiler/compile/render_dom/wrappers/Fragment.ts
@@ -65,7 +65,7 @@ export default class FragmentWrapper {
 		this.nodes = [];
 
 		let last_child: Wrapper;
-		let window_wrapper;
+		let window_wrapper: Window | undefined;
 
 		let i = nodes.length;
 		while (i--) {
diff --git a/src/compiler/compile/render_dom/wrappers/Head.ts b/src/compiler/compile/render_dom/wrappers/Head.ts
index 3869994ae4..7915604f98 100644
--- a/src/compiler/compile/render_dom/wrappers/Head.ts
+++ b/src/compiler/compile/render_dom/wrappers/Head.ts
@@ -33,7 +33,7 @@ export default class HeadWrapper extends Wrapper {
 	}
 
 	render(block: Block, _parent_node: Identifier, _parent_nodes: Identifier) {
-		let nodes;
+		let nodes: Identifier;
 		if (this.renderer.options.hydratable && this.fragment.nodes.length) {
 			nodes = block.get_unique_name('head_nodes');
 			block.chunks.claim.push(b`const ${nodes} = @head_selector('${this.node.id}', @_document.head);`);
diff --git a/src/compiler/compile/render_dom/wrappers/IfBlock.ts b/src/compiler/compile/render_dom/wrappers/IfBlock.ts
index d74ce270bf..9c4798c69c 100644
--- a/src/compiler/compile/render_dom/wrappers/IfBlock.ts
+++ b/src/compiler/compile/render_dom/wrappers/IfBlock.ts
@@ -13,6 +13,8 @@ import { Identifier, Node } from 'estree';
 import { push_array } from '../../../utils/push_array';
 import { add_const_tags, add_const_tags_context } from './shared/add_const_tags';
 
+type DetachingOrNull = 'detaching' | null;
+
 function is_else_if(node: ElseBlock) {
 	return (
 		node && node.children.length === 1 && node.children[0].type === 'IfBlock'
@@ -213,7 +215,7 @@ export default class IfBlockWrapper extends Wrapper {
 
 		const vars = { name, anchor, if_exists_condition, has_else, has_transitions };
 
-		const detaching = parent_node && !is_head(parent_node) ? null : 'detaching';
+		const detaching: DetachingOrNull = parent_node && !is_head(parent_node) ? null : 'detaching';
 
 		if (this.node.else) {
 			this.branches.forEach(branch => {
@@ -275,9 +277,9 @@ export default class IfBlockWrapper extends Wrapper {
 		block: Block,
 		parent_node: Identifier,
 		_parent_nodes: Identifier,
-		dynamic,
+		dynamic: boolean,
 		{ name, anchor, has_else, if_exists_condition, has_transitions },
-		detaching
+		detaching: DetachingOrNull
 	) {
 		const select_block_type = this.renderer.component.get_unique_name('select_block_type');
 		const current_block_type = block.get_unique_name('current_block_type');
@@ -414,9 +416,9 @@ export default class IfBlockWrapper extends Wrapper {
 		block: Block,
 		parent_node: Identifier,
 		_parent_nodes: Identifier,
-		dynamic,
+		dynamic: boolean,
 		{ name, anchor, has_else, has_transitions, if_exists_condition },
-		detaching
+		detaching: DetachingOrNull
 	) {
 		const select_block_type = this.renderer.component.get_unique_name('select_block_type');
 		const current_block_type_index = block.get_unique_name('current_block_type_index');
@@ -428,8 +430,8 @@ export default class IfBlockWrapper extends Wrapper {
 		const if_ctx = select_block_ctx ? x`${select_block_ctx}(#ctx, ${current_block_type_index})` : x`#ctx`;
 
 		const if_current_block_type_index = has_else
-			? nodes => nodes
-			: nodes => b`if (~${current_block_type_index}) { ${nodes} }`;
+			? (nodes: Node[]) => nodes
+			: (nodes: Node[]) => b`if (~${current_block_type_index}) { ${nodes} }`;
 
 		block.add_variable(current_block_type_index);
 		block.add_variable(name);
@@ -593,9 +595,9 @@ export default class IfBlockWrapper extends Wrapper {
 		block: Block,
 		parent_node: Identifier,
 		_parent_nodes: Identifier,
-		dynamic,
+		dynamic: boolean,
 		{ name, anchor, if_exists_condition, has_transitions },
-		detaching
+		detaching: DetachingOrNull
 	) {
 		const branch = this.branches[0];
 		const if_ctx = branch.get_ctx_name ? x`${branch.get_ctx_name}(#ctx)` : x`#ctx`;
diff --git a/src/compiler/compile/render_dom/wrappers/InlineComponent/index.ts b/src/compiler/compile/render_dom/wrappers/InlineComponent/index.ts
index 37416379c9..bca01fdb4c 100644
--- a/src/compiler/compile/render_dom/wrappers/InlineComponent/index.ts
+++ b/src/compiler/compile/render_dom/wrappers/InlineComponent/index.ts
@@ -139,7 +139,7 @@ export default class InlineComponentWrapper extends Wrapper {
 			child.render(block, null, x`#nodes` as Identifier);
 		});
 
-		let props;
+		let props: Identifier | undefined;
 		const name_changes = block.get_unique_name(`${name.name}_changes`);
 
 		const uses_spread = !!this.node.attributes.find(a => a.is_spread);
@@ -234,7 +234,7 @@ export default class InlineComponentWrapper extends Wrapper {
 						: null;
 					const unchanged = dependencies.size === 0;
 
-					let change_object;
+					let change_object: Node | ReturnType<typeof x>;
 					if (attr.is_spread) {
 						const value = attr.expression.manipulate(block);
 						initial_props.push(value);
diff --git a/src/compiler/compile/render_dom/wrappers/RawMustacheTag.ts b/src/compiler/compile/render_dom/wrappers/RawMustacheTag.ts
index 7810d8f099..8dc8460e1d 100644
--- a/src/compiler/compile/render_dom/wrappers/RawMustacheTag.ts
+++ b/src/compiler/compile/render_dom/wrappers/RawMustacheTag.ts
@@ -8,7 +8,7 @@ import Element from '../../nodes/Element';
 import MustacheTag from '../../nodes/MustacheTag';
 import RawMustacheTag from '../../nodes/RawMustacheTag';
 import { is_head } from './shared/is_head';
-import { Identifier } from 'estree';
+import { Identifier, Node } from 'estree';
 
 export default class RawMustacheTagWrapper extends Tag {
 	var: Identifier = { type: 'Identifier', name: 'raw' };
@@ -30,7 +30,7 @@ export default class RawMustacheTagWrapper extends Tag {
 		const can_use_innerhtml = !in_head && parent_node && !this.prev && !this.next;
 
 		if (can_use_innerhtml) {
-			const insert = content => b`${parent_node}.innerHTML = ${content};`[0];
+			const insert = (content: Node) => b`${parent_node}.innerHTML = ${content};`[0];
 
 			const { init } = this.rename_this_method(
 				block,
diff --git a/src/compiler/compile/render_dom/wrappers/Slot.ts b/src/compiler/compile/render_dom/wrappers/Slot.ts
index 5a778ba5fb..0a589e3394 100644
--- a/src/compiler/compile/render_dom/wrappers/Slot.ts
+++ b/src/compiler/compile/render_dom/wrappers/Slot.ts
@@ -9,7 +9,7 @@ import add_to_set from '../../utils/add_to_set';
 import get_slot_data from '../../utils/get_slot_data';
 import { is_reserved_keyword } from '../../utils/reserved_keywords';
 import is_dynamic from './shared/is_dynamic';
-import { Identifier, ObjectExpression } from 'estree';
+import { Identifier, ObjectExpression, Node } from 'estree';
 import create_debugging_comment from './shared/create_debugging_comment';
 
 export default class SlotWrapper extends Wrapper {
@@ -75,9 +75,9 @@ export default class SlotWrapper extends Wrapper {
 			block = this.slot_block;
 		}
 
-		let get_slot_changes_fn;
-		let get_slot_spread_changes_fn;
-		let get_slot_context_fn;
+		let get_slot_changes_fn: Identifier | 'null';
+		let get_slot_spread_changes_fn: Identifier | undefined;
+		let get_slot_context_fn: Identifier | 'null';
 
 		if (this.node.values.size > 0) {
 			get_slot_changes_fn = renderer.component.get_unique_name(`get_${sanitize(slot_name)}_slot_changes`);
@@ -176,7 +176,7 @@ export default class SlotWrapper extends Wrapper {
 		].filter(Boolean);
 		const all_dirty_condition = all_dirty_conditions.length ? all_dirty_conditions.reduce((condition1, condition2) => x`${condition1} || ${condition2}`) : null;
 
-		let slot_update;
+		let slot_update: Node[];
 		if (all_dirty_condition) {
 			const dirty = x`${all_dirty_condition} ? @get_all_dirty_from_scope(${renderer.reference('$$scope')}) : @get_slot_changes(${slot_definition}, ${renderer.reference('$$scope')}, #dirty, ${get_slot_changes_fn})`;
 
diff --git a/src/compiler/compile/render_dom/wrappers/Window.ts b/src/compiler/compile/render_dom/wrappers/Window.ts
index 3c55680446..c98af18268 100644
--- a/src/compiler/compile/render_dom/wrappers/Window.ts
+++ b/src/compiler/compile/render_dom/wrappers/Window.ts
@@ -45,7 +45,7 @@ export default class WindowWrapper extends Wrapper {
 		const { renderer } = this;
 		const { component } = renderer;
 
-		const events = {};
+		const events: Record<string, Array<{ name: string; value: string }>> = {};
 		const bindings: Record<string, string> = {};
 
 		add_actions(block, '@_window', this.node.actions);
diff --git a/src/compiler/compile/render_dom/wrappers/shared/add_actions.ts b/src/compiler/compile/render_dom/wrappers/shared/add_actions.ts
index 3b39494994..734cfea972 100644
--- a/src/compiler/compile/render_dom/wrappers/shared/add_actions.ts
+++ b/src/compiler/compile/render_dom/wrappers/shared/add_actions.ts
@@ -1,7 +1,7 @@
 import { b, x } from 'code-red';
 import Block from '../../Block';
 import Action from '../../../nodes/Action';
-import { Expression } from 'estree';
+import { Expression, Node } from 'estree';
 import is_contextual from '../../../nodes/shared/is_contextual';
 
 export default function add_actions(
@@ -16,8 +16,8 @@ const regex_invalid_variable_identifier_characters = /[^a-zA-Z0-9_$]/g;
 
 export function add_action(block: Block, target: string | Expression, action: Action) {
 	const { expression, template_scope } = action;
-	let snippet;
-	let dependencies;
+	let snippet: Node | undefined;
+	let dependencies: string[] | undefined;
 
 	if (expression) {
 		snippet = expression.manipulate(block);
diff --git a/src/compiler/compile/render_dom/wrappers/shared/create_debugging_comment.ts b/src/compiler/compile/render_dom/wrappers/shared/create_debugging_comment.ts
index 6512b42862..9e989dc49c 100644
--- a/src/compiler/compile/render_dom/wrappers/shared/create_debugging_comment.ts
+++ b/src/compiler/compile/render_dom/wrappers/shared/create_debugging_comment.ts
@@ -15,7 +15,7 @@ export default function create_debugging_comment(
 		while (source[c - 1] === '{') c -= 1;
 	}
 
-	let d;
+	let d: number;
 
 	if (node.type === 'InlineComponent' || node.type === 'Element' || node.type === 'SlotTemplate') {
 		if (node.children.length) {
diff --git a/src/compiler/compile/render_dom/wrappers/shared/get_slot_definition.ts b/src/compiler/compile/render_dom/wrappers/shared/get_slot_definition.ts
index 2279c7c845..2114096988 100644
--- a/src/compiler/compile/render_dom/wrappers/shared/get_slot_definition.ts
+++ b/src/compiler/compile/render_dom/wrappers/shared/get_slot_definition.ts
@@ -2,7 +2,7 @@ import Let from '../../../nodes/Let';
 import { x, p } from 'code-red';
 import Block from '../../Block';
 import TemplateScope from '../../../nodes/shared/TemplateScope';
-import { BinaryExpression } from 'estree';
+import { BinaryExpression, Identifier } from 'estree';
 
 export function get_slot_definition(block: Block, scope: TemplateScope, lets: Let[]) {
 	if (lets.length === 0) return { block, scope };
@@ -21,7 +21,7 @@ export function get_slot_definition(block: Block, scope: TemplateScope, lets: Le
 	const value_map = new Map();
 
 	lets.forEach(l => {
-		let value;
+		let value: Identifier;
 		if (l.names.length > 1) {
 			// more than one, probably destructuring
 			const unique_name = block.get_unique_name(l.names.join('_')).name;
@@ -86,7 +86,7 @@ export function get_slot_definition(block: Block, scope: TemplateScope, lets: Le
 					elements[g] = grouped[g]
 						? grouped[g]
 							.map(({ name, n }) => x`${name} ? ${1 << n} : 0`)
-							.reduce((lhs, rhs) => x`${lhs} | ${rhs}`)
+							.reduce((lhs: ReturnType<typeof x>, rhs: ReturnType<typeof x>) => x`${lhs} | ${rhs}`)
 						: x`0`;
 				}
 
diff --git a/src/compiler/compile/render_dom/wrappers/shared/is_head.ts b/src/compiler/compile/render_dom/wrappers/shared/is_head.ts
index 36bf571aad..da34274d5b 100644
--- a/src/compiler/compile/render_dom/wrappers/shared/is_head.ts
+++ b/src/compiler/compile/render_dom/wrappers/shared/is_head.ts
@@ -1,3 +1,5 @@
-export function is_head(node) {
-	return node && node.type === 'MemberExpression' && node.object.name === '@_document' && node.property.name === 'head';
+import { Node } from 'estree';
+
+export function is_head(node: Node) {
+	return node && node.type === 'MemberExpression' && node.object['name'] === '@_document' && node.property['name'] === 'head';
 }