Merge pull request #7403 from webpack/fix/7335

fix argument TDZ and shadowing

lib/Parser.js

@@ -1030,23 +1030,28 @@ class Parser extends Tapable {
 	}
 
 	walkForInStatement(statement) {
-		if (statement.left.type === "VariableDeclaration")
+		if (statement.left.type === "VariableDeclaration") {
 			this.walkVariableDeclaration(statement.left);
-		else this.walkPattern(statement.left);
+		} else {
+			this.walkPattern(statement.left);
+		}
 		this.walkExpression(statement.right);
 		this.walkStatement(statement.body);
 	}
 
 	prewalkForOfStatement(statement) {
-		if (statement.left.type === "VariableDeclaration")
+		if (statement.left.type === "VariableDeclaration") {
 			this.prewalkVariableDeclaration(statement.left);
+		}
 		this.prewalkStatement(statement.body);
 	}
 
 	walkForOfStatement(statement) {
-		if (statement.left.type === "VariableDeclaration")
+		if (statement.left.type === "VariableDeclaration") {
 			this.walkVariableDeclaration(statement.left);
-		else this.walkPattern(statement.left);
+		} else {
+			this.walkPattern(statement.left);
+		}
 		this.walkExpression(statement.right);
 		this.walkStatement(statement.body);
 	}
@@ -1062,8 +1067,10 @@ class Parser extends Tapable {
 	walkFunctionDeclaration(statement) {
 		const wasTopLevel = this.scope.topLevelScope;
 		this.scope.topLevelScope = false;
-		for (const param of statement.params) this.walkPattern(param);
 		this.inScope(statement.params, () => {
+			for (const param of statement.params) {
+				this.walkPattern(param);
+			}
 			if (statement.body.type === "BlockStatement") {
 				this.detectStrictMode(statement.body.body);
 				this.prewalkStatement(statement.body);
@@ -1355,13 +1362,10 @@ class Parser extends Tapable {
 	}
 
 	walkExpressions(expressions) {
-		for (
-			let expressionsIndex = 0, len = expressions.length;
-			expressionsIndex < len;
-			expressionsIndex++
-		) {
-			const expression = expressions[expressionsIndex];
-			if (expression) this.walkExpression(expression);
+		for (const expression of expressions) {
+			if (expression) {
+				this.walkExpression(expression);
+			}
 		}
 	}
 
@@ -1469,8 +1473,10 @@ class Parser extends Tapable {
 	walkFunctionExpression(expression) {
 		const wasTopLevel = this.scope.topLevelScope;
 		this.scope.topLevelScope = false;
-		for (const param of expression.params) this.walkPattern(param);
 		this.inScope(expression.params, () => {
+			for (const param of expression.params) {
+				this.walkPattern(param);
+			}
 			if (expression.body.type === "BlockStatement") {
 				this.detectStrictMode(expression.body.body);
 				this.prewalkStatement(expression.body);
@@ -1483,8 +1489,10 @@ class Parser extends Tapable {
 	}
 
 	walkArrowFunctionExpression(expression) {
-		for (const param of expression.params) this.walkPattern(param);
 		this.inScope(expression.params, () => {
+			for (const param of expression.params) {
+				this.walkPattern(param);
+			}
 			if (expression.body.type === "BlockStatement") {
 				this.detectStrictMode(expression.body.body);
 				this.prewalkStatement(expression.body);
@@ -1640,7 +1648,9 @@ class Parser extends Tapable {
 			if (functionExpression.body.type === "BlockStatement") {
 				this.prewalkStatement(functionExpression.body);
 				this.walkStatement(functionExpression.body);
-			} else this.walkExpression(functionExpression.body);
+			} else {
+				this.walkExpression(functionExpression.body);
+			}
 		});
 		this.scope.topLevelScope = wasTopLevel;
 	}
@@ -1743,13 +1753,7 @@ class Parser extends Tapable {
 
 		this.scope.renames.set("this", null);
 
-		for (
-			let paramIndex = 0, len = params.length;
-			paramIndex < len;
-			paramIndex++
-		) {
-			const param = params[paramIndex];
-
+		for (const param of params) {
 			if (typeof param !== "string") {
 				this.enterPattern(param, param => {
 					this.scope.renames.set(param, null);

test/cases/parsing/issue-7335/a.js

@@ -0,0 +1 @@
+export default 9;

test/cases/parsing/issue-7335/index.js

@@ -0,0 +1,27 @@
+import x from "./a";
+
+const sum1 = (x, y, total = x + y) => total;
+const id1 = (a = x) => a;
+
+function sum2(x, y, total = x + y) { return total; }
+function id2(a = x) { return a; }
+
+const sum3 = function(x, y, total = x + y) { return total; }
+const id3 = function(a = x) { return a; }
+
+it("should shadow imported bindings", () => {
+	// Arrow functions
+	expect(sum1(2, 3)).toBe(5);
+	expect(id1(1)).toBe(1);
+	expect(id1()).toBe(9);
+
+	// Function declarations
+	expect(sum2(2, 3)).toBe(5);
+	expect(id2(1)).toBe(1);
+	expect(id2()).toBe(9);
+
+	// Function expressions
+	expect(sum3(2, 3)).toBe(5);
+	expect(id3(1)).toBe(1);
+	expect(id3()).toBe(9);
+});