feature(fix): function parameter tracking

src/ast/nodes/ArrowFunctionExpression.ts

@@ -5,8 +5,9 @@ import type ChildScope from '../scopes/ChildScope';
 import ReturnValueScope from '../scopes/ReturnValueScope';
 import { type ObjectPath } from '../utils/PathTracker';
 import type BlockStatement from './BlockStatement';
+import type CallExpression from './CallExpression';
 import Identifier from './Identifier';
-import type * as NodeType from './NodeType';
+import * as NodeType from './NodeType';
 import { Flag, isFlagSet, setFlag } from './shared/BitFlags';
 import FunctionBase from './shared/FunctionBase';
 import type { ExpressionNode, IncludeChildren } from './shared/Node';
@@ -67,6 +68,13 @@ export default class ArrowFunctionExpression extends FunctionBase {
 		return false;
 	}
 
+	protected onlyFunctionCallUsed(): boolean {
+		const isIIFE =
+			this.parent.type === NodeType.CallExpression &&
+			(this.parent as CallExpression).callee === this;
+		return isIIFE || super.onlyFunctionCallUsed();
+	}
+
 	include(context: InclusionContext, includeChildrenRecursively: IncludeChildren): void {
 		super.include(context, includeChildrenRecursively);
 		for (const parameter of this.params) {

src/ast/nodes/CallExpression.ts

@@ -63,20 +63,17 @@ export default class CallExpression
 	}
 
 	hasEffects(context: HasEffectsContext): boolean {
-		try {
-			for (const argument of this.arguments) {
-				if (argument.hasEffects(context)) return true;
-			}
-			if (this.annotationPure) {
-				return false;
-			}
-			return (
-				this.callee.hasEffects(context) ||
-				this.callee.hasEffectsOnInteractionAtPath(EMPTY_PATH, this.interaction, context)
-			);
-		} finally {
-			if (!this.deoptimized) this.applyDeoptimizations();
+		if (!this.deoptimized) this.applyDeoptimizations();
+		for (const argument of this.arguments) {
+			if (argument.hasEffects(context)) return true;
 		}
+		if (this.annotationPure) {
+			return false;
+		}
+		return (
+			this.callee.hasEffects(context) ||
+			this.callee.hasEffectsOnInteractionAtPath(EMPTY_PATH, this.interaction, context)
+		);
 	}
 
 	include(context: InclusionContext, includeChildrenRecursively: IncludeChildren): void {

src/ast/nodes/FunctionDeclaration.ts

@@ -14,6 +14,11 @@ export default class FunctionDeclaration extends FunctionNode {
 		}
 	}
 
+	protected onlyFunctionCallUsed(): boolean {
+		// call super.onlyFunctionCallUsed for export default anonymous function
+		return this.id?.variable.getOnlyFunctionCallUsed() ?? super.onlyFunctionCallUsed();
+	}
+
 	parseNode(esTreeNode: GenericEsTreeNode): this {
 		if (esTreeNode.id !== null) {
 			this.id = new Identifier(this, this.scope.parent as ChildScope).parseNode(

src/ast/nodes/FunctionExpression.ts

@@ -2,6 +2,7 @@ import type MagicString from 'magic-string';
 import { BLANK } from '../../utils/blank';
 import type { NodeRenderOptions, RenderOptions } from '../../utils/renderHelpers';
 import ChildScope from '../scopes/ChildScope';
+import type CallExpression from './CallExpression';
 import type { IdentifierWithVariable } from './Identifier';
 import Identifier from './Identifier';
 import * as NodeType from './NodeType';
@@ -25,6 +26,14 @@ export default class FunctionExpression extends FunctionNode {
 		return super.parseNode(esTreeNode);
 	}
 
+	protected onlyFunctionCallUsed(): boolean {
+		const isIIFE =
+			this.parent.type === NodeType.CallExpression &&
+			(this.parent as CallExpression).callee === this &&
+			(this.id === null || this.id.variable.getOnlyFunctionCallUsed());
+		return isIIFE || super.onlyFunctionCallUsed();
+	}
+
 	render(
 		code: MagicString,
 		options: RenderOptions,

src/ast/nodes/Identifier.ts

@@ -60,10 +60,12 @@ export default class Identifier extends NodeBase implements PatternNode {
 		}
 	}
 
+	private isReferenceVariable = false;
 	bind(): void {
 		if (!this.variable && isReference(this, this.parent as NodeWithFieldDefinition)) {
 			this.variable = this.scope.findVariable(this.name);
 			this.variable.addReference(this);
+			this.isReferenceVariable = true;
 		}
 	}
 
@@ -295,6 +297,10 @@ export default class Identifier extends NodeBase implements PatternNode {
 			this.variable.consolidateInitializers();
 			this.scope.context.requestTreeshakingPass();
 		}
+		if (this.isReferenceVariable) {
+			this.variable!.addUsedPlace(this);
+			this.scope.context.requestTreeshakingPass();
+		}
 	}
 
 	private getVariableRespectingTDZ(): ExpressionEntity | null {

src/ast/nodes/MemberExpression.ts

@@ -396,6 +396,10 @@ export default class MemberExpression
 			);
 			this.scope.context.requestTreeshakingPass();
 		}
+		if (this.variable) {
+			this.variable.addUsedPlace(this);
+			this.scope.context.requestTreeshakingPass();
+		}
 	}
 
 	private applyAssignmentDeoptimization(): void {

src/ast/nodes/UpdateExpression.ts

@@ -87,7 +87,7 @@ export default class UpdateExpression extends NodeBase {
 		this.argument.deoptimizePath(EMPTY_PATH);
 		if (this.argument instanceof Identifier) {
 			const variable = this.scope.findVariable(this.argument.name);
-			variable.isReassigned = true;
+			variable.markReassigned();
 		}
 		this.scope.context.requestTreeshakingPass();
 	}

src/ast/nodes/shared/FunctionBase.ts

@@ -10,11 +10,16 @@ import {
 import type ReturnValueScope from '../../scopes/ReturnValueScope';
 import type { ObjectPath, PathTracker } from '../../utils/PathTracker';
 import { UNKNOWN_PATH, UnknownKey } from '../../utils/PathTracker';
+import { UNDEFINED_EXPRESSION } from '../../values';
 import type ParameterVariable from '../../variables/ParameterVariable';
+import type Variable from '../../variables/Variable';
 import BlockStatement from '../BlockStatement';
+import type ExportDefaultDeclaration from '../ExportDefaultDeclaration';
 import Identifier from '../Identifier';
+import * as NodeType from '../NodeType';
 import RestElement from '../RestElement';
 import type SpreadElement from '../SpreadElement';
+import type VariableDeclarator from '../VariableDeclarator';
 import { Flag, isFlagSet, setFlag } from './BitFlags';
 import type { ExpressionEntity, LiteralValueOrUnknown } from './Expression';
 import { UNKNOWN_EXPRESSION, UNKNOWN_RETURN_EXPRESSION } from './Expression';
@@ -27,6 +32,8 @@ import {
 import type { ObjectEntity } from './ObjectEntity';
 import type { PatternNode } from './Pattern';
 
+type InteractionCalledArguments = NodeInteractionCalled['args'];
+
 export default abstract class FunctionBase extends NodeBase {
 	declare body: BlockStatement | ExpressionNode;
 	declare params: PatternNode[];
@@ -57,6 +64,27 @@ export default abstract class FunctionBase extends NodeBase {
 		this.flags = setFlag(this.flags, Flag.generator, value);
 	}
 
+	private updateParameterVariableValues(_arguments: InteractionCalledArguments): void {
+		for (let position = 0; position < this.params.length; position++) {
+			const parameter = this.params[position];
+			if (!(parameter instanceof Identifier)) {
+				continue;
+			}
+			const parameterVariable = parameter.variable as ParameterVariable;
+			const argument = _arguments[position + 1] ?? UNDEFINED_EXPRESSION;
+			parameterVariable.updateKnownValue(argument);
+		}
+	}
+
+	private deoptimizeParameterVariableValues() {
+		for (const parameter of this.params) {
+			if (parameter instanceof Identifier) {
+				const parameterVariable = parameter.variable as ParameterVariable;
+				parameterVariable.markReassigned();
+			}
+		}
+	}
+
 	protected objectEntity: ObjectEntity | null = null;
 
 	deoptimizeArgumentsOnInteractionAtPath(
@@ -84,6 +112,7 @@ export default abstract class FunctionBase extends NodeBase {
 					this.addArgumentToBeDeoptimized(argument);
 				}
 			}
+			this.updateParameterVariableValues(args);
 		} else {
 			this.getObjectEntity().deoptimizeArgumentsOnInteractionAtPath(
 				interaction,
@@ -102,6 +131,7 @@ export default abstract class FunctionBase extends NodeBase {
 			for (const parameterList of this.scope.parameters) {
 				for (const parameter of parameterList) {
 					parameter.deoptimizePath(UNKNOWN_PATH);
+					parameter.markReassigned();
 				}
 			}
 		}
@@ -180,7 +210,26 @@ export default abstract class FunctionBase extends NodeBase {
 		return false;
 	}
 
+	/**
+	 * If the function (expression or declaration) is only used as function calls
+	 */
+	protected onlyFunctionCallUsed(): boolean {
+		let variable: Variable | null = null;
+		if (this.parent.type === NodeType.VariableDeclarator) {
+			variable = (this.parent as VariableDeclarator).id.variable ?? null;
+		}
+		if (this.parent.type === NodeType.ExportDefaultDeclaration) {
+			variable = (this.parent as ExportDefaultDeclaration).variable;
+		}
+		return variable?.getOnlyFunctionCallUsed() ?? false;
+	}
+
+	private parameterVariableValuesDeoptimized = false;
 	include(context: InclusionContext, includeChildrenRecursively: IncludeChildren): void {
+		if (!this.parameterVariableValuesDeoptimized && !this.onlyFunctionCallUsed()) {
+			this.parameterVariableValuesDeoptimized = true;
+			this.deoptimizeParameterVariableValues();
+		}
 		if (!this.deoptimized) this.applyDeoptimizations();
 		this.included = true;
 		const { brokenFlow } = context;

src/ast/variables/ExportDefaultVariable.ts

@@ -3,6 +3,7 @@ import ClassDeclaration from '../nodes/ClassDeclaration';
 import type ExportDefaultDeclaration from '../nodes/ExportDefaultDeclaration';
 import FunctionDeclaration from '../nodes/FunctionDeclaration';
 import Identifier, { type IdentifierWithVariable } from '../nodes/Identifier';
+import type { NodeBase } from '../nodes/shared/Node';
 import LocalVariable from './LocalVariable';
 import UndefinedVariable from './UndefinedVariable';
 import type Variable from './Variable';
@@ -37,6 +38,15 @@ export default class ExportDefaultVariable extends LocalVariable {
 		}
 	}
 
+	addUsedPlace(usedPlace: NodeBase): void {
+		const original = this.getOriginalVariable();
+		if (original === this) {
+			super.addUsedPlace(usedPlace);
+		} else {
+			original.addUsedPlace(usedPlace);
+		}
+	}
+
 	forbidName(name: string) {
 		const original = this.getOriginalVariable();
 		if (original === this) {

src/ast/variables/GlobalVariable.ts

@@ -13,9 +13,12 @@ import type { ObjectPath, PathTracker } from '../utils/PathTracker';
 import Variable from './Variable';
 
 export default class GlobalVariable extends Variable {
-	// Ensure we use live-bindings for globals as we do not know if they have
-	// been reassigned
-	isReassigned = true;
+	constructor(name: string) {
+		super(name);
+		// Ensure we use live-bindings for globals as we do not know if they have
+		// been reassigned
+		this.markReassigned();
+	}
 
 	deoptimizeArgumentsOnInteractionAtPath(
 		interaction: NodeInteraction,

src/ast/variables/LocalVariable.ts

@@ -91,7 +91,7 @@ export default class LocalVariable extends Variable {
 			return;
 		}
 		if (path.length === 0) {
-			this.isReassigned = true;
+			this.markReassigned();
 			const expressionsToBeDeoptimized = this.expressionsToBeDeoptimized;
 			this.expressionsToBeDeoptimized = EMPTY_ARRAY as unknown as DeoptimizableEntity[];
 			for (const expression of expressionsToBeDeoptimized) {
@@ -222,7 +222,7 @@ export default class LocalVariable extends Variable {
 		if (this.additionalInitializers === null) {
 			this.additionalInitializers = [this.init];
 			this.init = UNKNOWN_EXPRESSION;
-			this.isReassigned = true;
+			this.markReassigned();
 		}
 		return this.additionalInitializers;
 	}