Roll back parameter default tree shaking

src/ast/nodes/ArrayExpression.ts

@@ -85,11 +85,7 @@ export default class ArrayExpression extends NodeBase {
 			if (element) {
 				if (hasSpread || element instanceof SpreadElement) {
 					hasSpread = true;
-					// This also deoptimizes parameter defaults
 					element.deoptimizePath(UNKNOWN_PATH);
-				} else {
-					// We do not track parameter defaults in arrays
-					element.deoptimizeCallParameters();
 				}
 			}
 		}

src/ast/nodes/ArrowFunctionExpression.ts

@@ -1,12 +1,13 @@
 import { type CallOptions } from '../CallOptions';
-import { type HasEffectsContext } from '../ExecutionContext';
+import { type HasEffectsContext, InclusionContext } from '../ExecutionContext';
 import ReturnValueScope from '../scopes/ReturnValueScope';
 import type Scope from '../scopes/Scope';
 import { type ObjectPath } from '../utils/PathTracker';
 import BlockStatement from './BlockStatement';
+import Identifier from './Identifier';
 import * as NodeType from './NodeType';
 import FunctionBase from './shared/FunctionBase';
-import { type ExpressionNode } from './shared/Node';
+import { type ExpressionNode, IncludeChildren } from './shared/Node';
 import { ObjectEntity } from './shared/ObjectEntity';
 import { OBJECT_PROTOTYPE } from './shared/ObjectPrototype';
 import type { PatternNode } from './shared/Pattern';
@@ -48,6 +49,15 @@ export default class ArrowFunctionExpression extends FunctionBase {
 		return false;
 	}
 
+	include(context: InclusionContext, includeChildrenRecursively: IncludeChildren): void {
+		super.include(context, includeChildrenRecursively);
+		for (const param of this.params) {
+			if (!(param instanceof Identifier)) {
+				param.include(context, includeChildrenRecursively);
+			}
+		}
+	}
+
 	protected getObjectEntity(): ObjectEntity {
 		if (this.objectEntity !== null) {
 			return this.objectEntity;

src/ast/nodes/AssignmentPattern.ts

@@ -35,10 +35,8 @@ export default class AssignmentPattern extends NodeBase implements PatternNode {
 		return path.length > 0 || this.left.hasEffectsWhenAssignedAtPath(EMPTY_PATH, context);
 	}
 
-	// Note that FunctionBase may directly include .left and .right without
-	// including the pattern itself. This is how default parameter tree-shaking
-	// works at the moment.
 	include(context: InclusionContext, includeChildrenRecursively: IncludeChildren): void {
+		if (!this.deoptimized) this.applyDeoptimizations();
 		this.included = true;
 		this.left.include(context, includeChildrenRecursively);
 		this.right.include(context, includeChildrenRecursively);

src/ast/nodes/CallExpression.ts

@@ -95,7 +95,7 @@ export default class CallExpression extends CallExpressionBase implements Deopti
 			}
 		} else {
 			this.included = true;
-			this.callee.include(context, false, { includeWithoutParameterDefaults: true });
+			this.callee.include(context, false);
 		}
 		this.callee.includeCallArguments(context, this.arguments);
 		const returnExpression = this.getReturnExpression();

src/ast/nodes/FunctionDeclaration.ts

@@ -1,17 +1,12 @@
-import { InclusionContext } from '../ExecutionContext';
 import type ChildScope from '../scopes/ChildScope';
 import Identifier, { type IdentifierWithVariable } from './Identifier';
 import type * as NodeType from './NodeType';
 import FunctionNode from './shared/FunctionNode';
-import type { GenericEsTreeNode, IncludeChildren } from './shared/Node';
+import type { GenericEsTreeNode } from './shared/Node';
 
 export default class FunctionDeclaration extends FunctionNode {
 	declare type: NodeType.tFunctionDeclaration;
 
-	include(context: InclusionContext, includeChildrenRecursively: IncludeChildren) {
-		super.include(context, includeChildrenRecursively, { includeWithoutParameterDefaults: true });
-	}
-
 	initialise(): void {
 		super.initialise();
 		if (this.id !== null) {

src/ast/nodes/Identifier.ts

@@ -86,10 +86,6 @@ export default class Identifier extends NodeBase implements PatternNode {
 		return [(this.variable = variable)];
 	}
 
-	deoptimizeCallParameters() {
-		this.variable!.deoptimizeCallParameters();
-	}
-
 	deoptimizePath(path: ObjectPath): void {
 		if (path.length === 0 && !this.scope.contains(this.name)) {
 			this.disallowImportReassignment();

src/ast/nodes/ObjectExpression.ts

@@ -102,14 +102,7 @@ export default class ObjectExpression extends NodeBase implements DeoptimizableE
 		}
 	}
 
-	protected applyDeoptimizations() {
-		this.deoptimized = true;
-		for (const property of this.properties) {
-			if (property instanceof Property) {
-				property.value.deoptimizeCallParameters();
-			}
-		}
-	}
+	protected applyDeoptimizations() {}
 
 	private getObjectEntity(): ObjectEntity {
 		if (this.objectEntity !== null) {

src/ast/nodes/VariableDeclarator.ts

@@ -35,9 +35,7 @@ export default class VariableDeclarator extends NodeBase {
 
 	include(context: InclusionContext, includeChildrenRecursively: IncludeChildren): void {
 		this.included = true;
-		this.init?.include(context, includeChildrenRecursively, {
-			includeWithoutParameterDefaults: true
-		});
+		this.init?.include(context, includeChildrenRecursively);
 		this.id.markDeclarationReached();
 		if (includeChildrenRecursively || this.id.shouldBeIncluded(context)) {
 			this.id.include(context, includeChildrenRecursively);

src/ast/nodes/YieldExpression.ts

@@ -11,7 +11,7 @@ export default class YieldExpression extends NodeBase {
 
 	hasEffects(context: HasEffectsContext): boolean {
 		if (!this.deoptimized) this.applyDeoptimizations();
-		return !context.ignore.returnYield || !!this.argument?.hasEffects(context);
+		return !(context.ignore.returnYield && !this.argument?.hasEffects(context));
 	}
 
 	render(code: MagicString, options: RenderOptions): void {

src/ast/nodes/shared/ClassNode.ts

@@ -16,7 +16,6 @@ import type ClassBody from '../ClassBody';
 import Identifier from '../Identifier';
 import type Literal from '../Literal';
 import MethodDefinition from '../MethodDefinition';
-import PropertyDefinition from '../PropertyDefinition';
 import { type ExpressionEntity, type LiteralValueOrUnknown } from './Expression';
 import { type ExpressionNode, type IncludeChildren, NodeBase } from './Node';
 import { ObjectEntity, type ObjectProperty } from './ObjectEntity';
@@ -40,12 +39,6 @@ export default class ClassNode extends NodeBase implements DeoptimizableEntity {
 
 	deoptimizePath(path: ObjectPath): void {
 		this.getObjectEntity().deoptimizePath(path);
-		if (path.length === 1 && path[0] === UnknownKey) {
-			// A reassignment of UNKNOWN_PATH is considered equivalent to having lost track
-			// which means the constructor needs to be reassigned
-			this.classConstructor?.deoptimizePath(UNKNOWN_PATH);
-			this.superClass?.deoptimizePath(UNKNOWN_PATH);
-		}
 	}
 
 	deoptimizeThisOnEventAtPath(
@@ -150,11 +143,8 @@ export default class ClassNode extends NodeBase implements DeoptimizableEntity {
 			) {
 				// Calls to methods are not tracked, ensure that the return value is deoptimized
 				definition.deoptimizePath(UNKNOWN_PATH);
-			} else if (definition instanceof PropertyDefinition) {
-				definition.value?.deoptimizeCallParameters();
 			}
 		}
-		this.superClass?.deoptimizeCallParameters();
 		this.context.requestTreeshakingPass();
 	}
 

src/ast/nodes/shared/Expression.ts

@@ -18,14 +18,11 @@ export interface InclusionOptions {
 	 * Include the id of a declarator even if unused to ensure it is a valid statement.
 	 */
 	asSingleStatement?: boolean;
-	includeWithoutParameterDefaults?: boolean;
 }
 
 export class ExpressionEntity implements WritableEntity {
 	included = false;
 
-	deoptimizeCallParameters(): void {}
-
 	deoptimizePath(_path: ObjectPath): void {}
 
 	deoptimizeThisOnEventAtPath(

src/ast/nodes/shared/FunctionBase.ts

@@ -1,5 +1,4 @@
 import type { NormalizedTreeshakingOptions } from '../../../rollup/types';
-import { BLANK } from '../../../utils/blank';
 import { type CallOptions, NO_ARGS } from '../../CallOptions';
 import { DeoptimizableEntity } from '../../DeoptimizableEntity';
 import {
@@ -9,27 +8,12 @@ import {
 } from '../../ExecutionContext';
 import { NodeEvent } from '../../NodeEvents';
 import ReturnValueScope from '../../scopes/ReturnValueScope';
-import {
-	EMPTY_PATH,
-	type ObjectPath,
-	PathTracker,
-	SHARED_RECURSION_TRACKER,
-	UNKNOWN_PATH,
-	UnknownKey
-} from '../../utils/PathTracker';
-import LocalVariable from '../../variables/LocalVariable';
-import AssignmentPattern from '../AssignmentPattern';
+import { type ObjectPath, PathTracker, UNKNOWN_PATH, UnknownKey } from '../../utils/PathTracker';
 import BlockStatement from '../BlockStatement';
 import * as NodeType from '../NodeType';
 import RestElement from '../RestElement';
 import type SpreadElement from '../SpreadElement';
-import {
-	type ExpressionEntity,
-	InclusionOptions,
-	LiteralValueOrUnknown,
-	UNKNOWN_EXPRESSION,
-	UnknownValue
-} from './Expression';
+import { type ExpressionEntity, LiteralValueOrUnknown, UNKNOWN_EXPRESSION } from './Expression';
 import {
 	type ExpressionNode,
 	type GenericEsTreeNode,
@@ -39,31 +23,20 @@ import {
 import { ObjectEntity } from './ObjectEntity';
 import type { PatternNode } from './Pattern';
 
-export default abstract class FunctionBase extends NodeBase implements DeoptimizableEntity {
+export default abstract class FunctionBase extends NodeBase {
 	declare async: boolean;
 	declare body: BlockStatement | ExpressionNode;
 	declare params: readonly PatternNode[];
 	declare preventChildBlockScope: true;
 	declare scope: ReturnValueScope;
 	protected objectEntity: ObjectEntity | null = null;
 	private deoptimizedReturn = false;
-	private forceIncludeParameters = false;
-	private declare parameterVariables: LocalVariable[][];
-
-	deoptimizeCache() {
-		this.forceIncludeParameters = true;
-	}
-
-	deoptimizeCallParameters() {
-		this.forceIncludeParameters = true;
-	}
 
 	deoptimizePath(path: ObjectPath): void {
 		this.getObjectEntity().deoptimizePath(path);
 		if (path.length === 1 && path[0] === UnknownKey) {
 			// A reassignment of UNKNOWN_PATH is considered equivalent to having lost track
 			// which means the return expression needs to be reassigned
-			this.forceIncludeParameters = true;
 			this.scope.getReturnExpression().deoptimizePath(UNKNOWN_PATH);
 		}
 	}
@@ -150,89 +123,31 @@ export default abstract class FunctionBase extends NodeBase implements Deoptimiz
 				return true;
 			}
 		}
-		for (let position = 0; position < this.params.length; position++) {
-			const parameter = this.params[position];
-			if (parameter instanceof AssignmentPattern) {
-				if (parameter.left.hasEffects(context)) {
-					return true;
-				}
-				const argumentValue = callOptions.args[position]?.getLiteralValueAtPath(
-					EMPTY_PATH,
-					SHARED_RECURSION_TRACKER,
-					this
-				);
-				if (
-					(argumentValue === undefined || argumentValue === UnknownValue) &&
-					parameter.right.hasEffects(context)
-				) {
-					return true;
-				}
-			} else if (parameter.hasEffects(context)) {
-				return true;
-			}
+		for (const param of this.params) {
+			if (param.hasEffects(context)) return true;
 		}
 		return false;
 	}
 
-	include(
-		context: InclusionContext,
-		includeChildrenRecursively: IncludeChildren,
-		{ includeWithoutParameterDefaults }: InclusionOptions = BLANK
-	): void {
+	include(context: InclusionContext, includeChildrenRecursively: IncludeChildren): void {
 		if (!this.deoptimized) this.applyDeoptimizations();
 		this.included = true;
 		const { brokenFlow } = context;
 		context.brokenFlow = BROKEN_FLOW_NONE;
 		this.body.include(context, includeChildrenRecursively);
 		context.brokenFlow = brokenFlow;
-		if (
-			!includeWithoutParameterDefaults ||
-			includeChildrenRecursively ||
-			this.forceIncludeParameters
-		) {
-			for (const param of this.params) {
-				param.include(context, includeChildrenRecursively);
-			}
-		}
 	}
 
 	includeCallArguments(
 		context: InclusionContext,
 		args: readonly (ExpressionEntity | SpreadElement)[]
 	): void {
-		for (let position = 0; position < this.params.length; position++) {
-			const parameter = this.params[position];
-			if (parameter instanceof AssignmentPattern) {
-				if (parameter.left.shouldBeIncluded(context)) {
-					parameter.left.include(context, false);
-				}
-				const argumentValue = args[position]?.getLiteralValueAtPath(
-					EMPTY_PATH,
-					SHARED_RECURSION_TRACKER,
-					this
-				);
-				// If argumentValue === UnknownTruthyValue, then we do not need to
-				// include the default
-				if (
-					(argumentValue === undefined || argumentValue === UnknownValue) &&
-					(this.parameterVariables[position].some(variable => variable.included) ||
-						parameter.right.shouldBeIncluded(context))
-				) {
-					parameter.right.include(context, false);
-				}
-			} else if (parameter.shouldBeIncluded(context)) {
-				parameter.include(context, false);
-			}
-		}
 		this.scope.includeCallArguments(context, args);
 	}
 
 	initialise(): void {
-		this.parameterVariables = this.params.map(param =>
-			param.declare('parameter', UNKNOWN_EXPRESSION)
-		);
 		this.scope.addParameterVariables(
-			this.parameterVariables,
+			this.params.map(param => param.declare('parameter', UNKNOWN_EXPRESSION)),
 			this.params[this.params.length - 1] instanceof RestElement
 		);
 		if (this.body instanceof BlockStatement) {
@@ -249,15 +164,7 @@ export default abstract class FunctionBase extends NodeBase implements Deoptimiz
 		super.parseNode(esTreeNode);
 	}
 
-	protected applyDeoptimizations() {
-		// We currently do not track deoptimizations of default values, deoptimize them
-		// just as we deoptimize call arguments
-		for (const param of this.params) {
-			if (param instanceof AssignmentPattern) {
-				param.right.deoptimizePath(UNKNOWN_PATH);
-			}
-		}
-	}
+	protected applyDeoptimizations() {}
 
 	protected abstract getObjectEntity(): ObjectEntity;
 }

src/ast/nodes/shared/FunctionNode.ts

@@ -1,12 +1,11 @@
-import { BLANK } from '../../../utils/blank';
 import { type CallOptions } from '../../CallOptions';
 import { type HasEffectsContext, type InclusionContext } from '../../ExecutionContext';
 import { EVENT_CALLED, type NodeEvent } from '../../NodeEvents';
 import FunctionScope from '../../scopes/FunctionScope';
 import { type ObjectPath, PathTracker } from '../../utils/PathTracker';
 import BlockStatement from '../BlockStatement';
-import { type IdentifierWithVariable } from '../Identifier';
-import { type ExpressionEntity, InclusionOptions, UNKNOWN_EXPRESSION } from './Expression';
+import Identifier, { type IdentifierWithVariable } from '../Identifier';
+import { type ExpressionEntity, UNKNOWN_EXPRESSION } from './Expression';
 import FunctionBase from './FunctionBase';
 import { type IncludeChildren } from './Node';
 import { ObjectEntity } from './ObjectEntity';
@@ -74,16 +73,15 @@ export default class FunctionNode extends FunctionBase {
 		return false;
 	}
 
-	include(
-		context: InclusionContext,
-		includeChildrenRecursively: IncludeChildren,
-		{ includeWithoutParameterDefaults }: InclusionOptions = BLANK
-	): void {
+	include(context: InclusionContext, includeChildrenRecursively: IncludeChildren): void {
+		super.include(context, includeChildrenRecursively);
 		this.id?.include();
-		super.include(context, includeChildrenRecursively, {
-			includeWithoutParameterDefaults:
-				includeWithoutParameterDefaults && !this.scope.argumentsVariable.included
-		});
+		const hasArguments = this.scope.argumentsVariable.included;
+		for (const param of this.params) {
+			if (!(param instanceof Identifier) || hasArguments) {
+				param.include(context, includeChildrenRecursively);
+			}
+		}
 	}
 
 	initialise(): void {