fix: 重複キーをエラーにする (#1018)

* Disallow duplicate key

* changelog

Author: uzmoi

src/parser/syntaxes/expressions.ts

@@ -593,6 +593,9 @@ function parseObject(s: ITokenStream, isStatic: boolean): Ast.Obj {
 	const map = new Map<string, Ast.Expression>();
 	while (!s.is(TokenKind.CloseBrace)) {
 		const k = parseObjectKey(s);
+		if (map.has(k)) {
+			throw new AiScriptSyntaxError(`Key ${k} is duplicated.`, s.getPos());
+		}
 		s.next();
 
 		s.expect(TokenKind.Colon);

test/literals.ts

@@ -251,6 +251,12 @@ describe('literal', () => {
 		`)).rejects.toThrow(AiScriptSyntaxError);
 	})
 
+	test.concurrent('obj (duplicate key)', async () => {
+		await expect(() => exe(`
+			<: { hoge: 1, hoge: 2 }
+		`)).rejects.toThrow(AiScriptSyntaxError);
+	});
+
 	test.concurrent('obj (invalid key)', async () => {
 		assert.rejects(() => exe(`
 		<: {

unreleased/dupe-key-to-syntax-error.md

@@ -0,0 +1 @@
+- Fix: オブジェクトリテラルでキーの重複がエラーになるように修正