Use flags over labels for simplicity and performance

src/ast/ExecutionContext.ts

@@ -3,19 +3,19 @@ import type { ExpressionEntity } from './nodes/shared/Expression';
 import { DiscriminatedPathTracker, PathTracker } from './utils/PathTracker';
 import type ThisVariable from './variables/ThisVariable';
 
-export const UnlabeledBreak = Symbol('Unlabeled Break');
-export const UnlabeledContinue = Symbol('Unlabeled Continue');
-export type Label = string | typeof UnlabeledBreak | typeof UnlabeledContinue;
-
 interface ExecutionContextIgnore {
-	labels: Set<Label>;
+	breaks: boolean;
+	continues: boolean;
+	labels: Set<string>;
 	returnYield: boolean;
 	this: boolean;
 }
 
 interface ControlFlowContext {
 	brokenFlow: boolean;
-	includedLabels: Set<Label>;
+	hasBreak: boolean;
+	hasContinue: boolean;
+	includedLabels: Set<string>;
 }
 
 export interface InclusionContext extends ControlFlowContext {
@@ -35,6 +35,8 @@ export interface HasEffectsContext extends ControlFlowContext {
 export function createInclusionContext(): InclusionContext {
 	return {
 		brokenFlow: false,
+		hasBreak: false,
+		hasContinue: false,
 		includedCallArguments: new Set(),
 		includedLabels: new Set()
 	};
@@ -46,7 +48,11 @@ export function createHasEffectsContext(): HasEffectsContext {
 		assigned: new PathTracker(),
 		brokenFlow: false,
 		called: new DiscriminatedPathTracker(),
+		hasBreak: false,
+		hasContinue: false,
 		ignore: {
+			breaks: false,
+			continues: false,
 			labels: new Set(),
 			returnYield: false,
 			this: false

src/ast/nodes/ArrowFunctionExpression.ts

@@ -40,6 +40,8 @@ export default class ArrowFunctionExpression extends FunctionBase {
 		if (interaction.type === INTERACTION_CALLED) {
 			const { ignore, brokenFlow } = context;
 			context.ignore = {
+				breaks: false,
+				continues: false,
 				labels: new Set(),
 				returnYield: true,
 				this: false

src/ast/nodes/BreakStatement.ts

@@ -1,4 +1,4 @@
-import { type HasEffectsContext, type InclusionContext, UnlabeledBreak } from '../ExecutionContext';
+import { type HasEffectsContext, type InclusionContext } from '../ExecutionContext';
 import type Identifier from './Identifier';
 import type * as NodeType from './NodeType';
 import { StatementBase } from './shared/Node';
@@ -8,9 +8,13 @@ export default class BreakStatement extends StatementBase {
 	declare type: NodeType.tBreakStatement;
 
 	hasEffects(context: HasEffectsContext): boolean {
-		const labelName = this.label?.name || UnlabeledBreak;
-		if (!context.ignore.labels.has(labelName)) return true;
-		context.includedLabels.add(labelName);
+		if (this.label) {
+			if (!context.ignore.labels.has(this.label.name)) return true;
+			context.includedLabels.add(this.label.name);
+		} else {
+			if (!context.ignore.breaks) return true;
+			context.hasBreak = true;
+		}
 		context.brokenFlow = true;
 		return false;
 	}
@@ -21,7 +25,7 @@ export default class BreakStatement extends StatementBase {
 			this.label.include();
 			context.includedLabels.add(this.label.name);
 		} else {
-			context.includedLabels.add(UnlabeledBreak);
+			context.hasBreak = true;
 		}
 		context.brokenFlow = true;
 	}

src/ast/nodes/ContinueStatement.ts

@@ -1,8 +1,4 @@
-import {
-	type HasEffectsContext,
-	type InclusionContext,
-	UnlabeledContinue
-} from '../ExecutionContext';
+import { type HasEffectsContext, type InclusionContext } from '../ExecutionContext';
 import type Identifier from './Identifier';
 import type * as NodeType from './NodeType';
 import { StatementBase } from './shared/Node';
@@ -12,9 +8,13 @@ export default class ContinueStatement extends StatementBase {
 	declare type: NodeType.tContinueStatement;
 
 	hasEffects(context: HasEffectsContext): boolean {
-		const labelName = this.label?.name || UnlabeledContinue;
-		if (!context.ignore.labels.has(labelName)) return true;
-		context.includedLabels.add(labelName);
+		if (this.label) {
+			if (!context.ignore.labels.has(this.label.name)) return true;
+			context.includedLabels.add(this.label.name);
+		} else {
+			if (!context.ignore.continues) return true;
+			context.hasContinue = true;
+		}
 		context.brokenFlow = true;
 		return false;
 	}
@@ -25,7 +25,7 @@ export default class ContinueStatement extends StatementBase {
 			this.label.include();
 			context.includedLabels.add(this.label.name);
 		} else {
-			context.includedLabels.add(UnlabeledContinue);
+			context.hasContinue = true;
 		}
 		context.brokenFlow = true;
 	}

src/ast/nodes/SwitchStatement.ts

@@ -3,8 +3,7 @@ import { type RenderOptions, renderStatementList } from '../../utils/renderHelpe
 import {
 	createHasEffectsContext,
 	type HasEffectsContext,
-	type InclusionContext,
-	UnlabeledBreak
+	type InclusionContext
 } from '../ExecutionContext';
 import BlockScope from '../scopes/BlockScope';
 import type Scope from '../scopes/Scope';
@@ -25,37 +24,31 @@ export default class SwitchStatement extends StatementBase {
 
 	hasEffects(context: HasEffectsContext): boolean {
 		if (this.discriminant.hasEffects(context)) return true;
-		const {
-			brokenFlow,
-			includedLabels,
-			ignore: { labels }
-		} = context;
-		const ignoreBreaks = labels.has(UnlabeledBreak);
-		labels.add(UnlabeledBreak);
-		const hasBreak = includedLabels.delete(UnlabeledBreak);
+		const { brokenFlow, hasBreak, ignore } = context;
+		const { breaks } = ignore;
+		ignore.breaks = true;
+		context.hasBreak = false;
 		let onlyHasBrokenFlow = true;
 		for (const switchCase of this.cases) {
 			if (switchCase.hasEffects(context)) return true;
 			// eslint-disable-next-line unicorn/consistent-destructuring
-			onlyHasBrokenFlow &&= context.brokenFlow && !includedLabels.has(UnlabeledBreak);
-			includedLabels.delete(UnlabeledBreak);
+			onlyHasBrokenFlow &&= context.brokenFlow && !context.hasBreak;
+			context.hasBreak = false;
 			context.brokenFlow = brokenFlow;
 		}
 		if (this.defaultCase !== null) {
 			context.brokenFlow = onlyHasBrokenFlow;
 		}
-		if (hasBreak) {
-			includedLabels.add(UnlabeledBreak);
-		}
-		if (!ignoreBreaks) labels.delete(UnlabeledBreak);
+		ignore.breaks = breaks;
+		context.hasBreak = hasBreak;
 		return false;
 	}
 
 	include(context: InclusionContext, includeChildrenRecursively: IncludeChildren): void {
 		this.included = true;
 		this.discriminant.include(context, includeChildrenRecursively);
-		const { brokenFlow, includedLabels } = context;
-		const hasBreak = includedLabels.delete(UnlabeledBreak);
+		const { brokenFlow, hasBreak } = context;
+		context.hasBreak = false;
 		let onlyHasBrokenFlow = true;
 		let isCaseIncluded =
 			includeChildrenRecursively ||
@@ -67,14 +60,14 @@ export default class SwitchStatement extends StatementBase {
 			}
 			if (!isCaseIncluded) {
 				const hasEffectsContext = createHasEffectsContext();
-				hasEffectsContext.ignore.labels.add(UnlabeledBreak);
+				hasEffectsContext.ignore.breaks = true;
 				isCaseIncluded = switchCase.hasEffects(hasEffectsContext);
 			}
 			if (isCaseIncluded) {
 				switchCase.include(context, includeChildrenRecursively);
 				// eslint-disable-next-line unicorn/consistent-destructuring
-				onlyHasBrokenFlow &&= context.brokenFlow && !includedLabels.has(UnlabeledBreak);
-				includedLabels.delete(UnlabeledBreak);
+				onlyHasBrokenFlow &&= context.brokenFlow && !context.hasBreak;
+				context.hasBreak = false;
 				context.brokenFlow = brokenFlow;
 			} else {
 				onlyHasBrokenFlow = brokenFlow;
@@ -83,9 +76,7 @@ export default class SwitchStatement extends StatementBase {
 		if (isCaseIncluded && this.defaultCase !== null) {
 			context.brokenFlow = onlyHasBrokenFlow;
 		}
-		if (hasBreak) {
-			includedLabels.add(UnlabeledBreak);
-		}
+		context.hasBreak = hasBreak;
 	}
 
 	initialise(): void {

src/ast/nodes/TryStatement.ts

@@ -1,5 +1,5 @@
 import type { NormalizedTreeshakingOptions } from '../../rollup/types';
-import type { HasEffectsContext, InclusionContext, Label } from '../ExecutionContext';
+import type { HasEffectsContext, InclusionContext } from '../ExecutionContext';
 import type BlockStatement from './BlockStatement';
 import type CatchClause from './CatchClause';
 import type * as NodeType from './NodeType';
@@ -12,7 +12,7 @@ export default class TryStatement extends StatementBase {
 	declare type: NodeType.tTryStatement;
 
 	private directlyIncluded = false;
-	private includedLabelsAfterBlock: Label[] | null = null;
+	private includedLabelsAfterBlock: string[] | null = null;
 
 	hasEffects(context: HasEffectsContext): boolean {
 		return (

src/ast/nodes/shared/FunctionNode.ts

@@ -60,6 +60,8 @@ export default class FunctionNode extends FunctionBase {
 			);
 			const { brokenFlow, ignore, replacedVariableInits } = context;
 			context.ignore = {
+				breaks: false,
+				continues: false,
 				labels: new Set(),
 				returnYield: true,
 				this: interaction.withNew

src/ast/nodes/shared/loops.ts

@@ -1,32 +1,18 @@
 import type { HasEffectsContext, InclusionContext } from '../../ExecutionContext';
-import { UnlabeledBreak, UnlabeledContinue } from '../../ExecutionContext';
 import type { StatementNode } from './Node';
 
 export function hasLoopBodyEffects(context: HasEffectsContext, body: StatementNode): boolean {
-	const {
-		brokenFlow,
-		includedLabels,
-		ignore: { labels }
-	} = context;
-	const hasBreak = includedLabels.delete(UnlabeledBreak);
-	const ignoreBreaks = labels.has(UnlabeledBreak);
-	labels.add(UnlabeledBreak);
-	const hasContinue = includedLabels.delete(UnlabeledContinue);
-	const ignoreContinues = labels.has(UnlabeledContinue);
-	labels.add(UnlabeledContinue);
+	const { brokenFlow, hasBreak, hasContinue, ignore } = context;
+	const { breaks, continues } = ignore;
+	ignore.breaks = true;
+	ignore.continues = true;
+	context.hasBreak = false;
+	context.hasContinue = false;
 	if (body.hasEffects(context)) return true;
-	if (!ignoreBreaks) labels.delete(UnlabeledBreak);
-	if (!ignoreContinues) labels.delete(UnlabeledContinue);
-	if (hasBreak) {
-		includedLabels.add(UnlabeledBreak);
-	} else {
-		includedLabels.delete(UnlabeledBreak);
-	}
-	if (hasContinue) {
-		includedLabels.add(UnlabeledContinue);
-	} else {
-		includedLabels.delete(UnlabeledContinue);
-	}
+	ignore.breaks = breaks;
+	ignore.continues = continues;
+	context.hasBreak = hasBreak;
+	context.hasContinue = hasContinue;
 	context.brokenFlow = brokenFlow;
 	return false;
 }
@@ -36,19 +22,11 @@ export function includeLoopBody(
 	body: StatementNode,
 	includeChildrenRecursively: boolean | 'variables'
 ) {
-	const { brokenFlow, includedLabels } = context;
-	const hasBreak = includedLabels.delete(UnlabeledBreak);
-	const hasContinue = includedLabels.delete(UnlabeledContinue);
+	const { brokenFlow, hasBreak, hasContinue } = context;
+	context.hasBreak = false;
+	context.hasContinue = false;
 	body.include(context, includeChildrenRecursively, { asSingleStatement: true });
-	if (hasBreak) {
-		includedLabels.add(UnlabeledBreak);
-	} else {
-		includedLabels.delete(UnlabeledBreak);
-	}
-	if (hasContinue) {
-		includedLabels.add(UnlabeledContinue);
-	} else {
-		includedLabels.delete(UnlabeledContinue);
-	}
+	context.hasBreak = hasBreak;
+	context.hasContinue = hasContinue;
 	context.brokenFlow = brokenFlow;
 }