Avoid name conflicts for default exported classes (#4756)

* Avoid name conflicts for default exported classes

* Improve coverage

src/ast/variables/ExportDefaultVariable.ts

@@ -37,6 +37,15 @@ export default class ExportDefaultVariable extends LocalVariable {
 		}
 	}
 
+	forbidName(name: string) {
+		const original = this.getOriginalVariable();
+		if (original === this) {
+			super.forbidName(name);
+		} else {
+			original.forbidName(name);
+		}
+	}
+
 	getAssignedVariableName(): string | null {
 		return (this.originalId && this.originalId.name) || null;
 	}

test/function/samples/class-name-conflict-3/_config.js

@@ -0,0 +1,3 @@
+module.exports = {
+	description: 'does not shadow variables when preserving class names'
+};

test/function/samples/class-name-conflict-3/foo.js

@@ -0,0 +1 @@
+export default class Foo {}

test/function/samples/class-name-conflict-3/main.js

@@ -0,0 +1,14 @@
+import Bar from './foo';
+
+const wrapper = () => {
+	class Foo extends Bar {
+		static assertName() {
+			assert.strictEqual(this.name, 'Foo');
+			assert.strictEqual(super.name, 'Foo');
+		}
+	}
+
+	return Foo;
+};
+
+wrapper().assertName();

test/function/samples/class-name-conflict-4/_config.js

@@ -0,0 +1,3 @@
+module.exports = {
+	description: 'does not shadow variables when preserving class names'
+};

test/function/samples/class-name-conflict-4/foo.js

@@ -0,0 +1,5 @@
+var Foo = class {};
+
+export default Foo;
+
+Foo = 'reassigned';

test/function/samples/class-name-conflict-4/main.js

@@ -0,0 +1,14 @@
+import Bar from './reexport';
+
+const wrapper = () => {
+	class Foo extends Bar {
+		static assertName() {
+			assert.strictEqual(this.name, 'Foo');
+			assert.strictEqual(super.name, 'Foo');
+		}
+	}
+
+	return Foo;
+};
+
+wrapper().assertName();

test/function/samples/class-name-conflict-4/reexport.js

@@ -0,0 +1,2 @@
+import Foo from './foo';
+export default Foo;