feat: オブジェクトリテラルで省略記法を使用可能にする (#1023)

* オブジェクトリテラル内で省略記法に対応

* fix: isStaticが真ならショートハンド構文を無効化

* fix: キーがIdentifierなときにのみ使用可能にする

* fix lint

Author: uzmoi

src/parser/syntaxes/expressions.ts

@@ -577,7 +577,7 @@ function parseReference(s: ITokenStream): Ast.Identifier {
 
 /**
  * ```abnf
- * Object = "{" [ObjectKey ":" Expr *(SEP IDENT ":" Expr) [SEP]] "}"
+ * Object = "{" [(ObjectKey ":" Expr / IDENT) *(SEP (ObjectKey ":" Expr / IDENT)) [SEP]] "}"
  * ```
 */
 function parseObject(s: ITokenStream, isStatic: boolean): Ast.Obj {
@@ -592,16 +592,25 @@ function parseObject(s: ITokenStream, isStatic: boolean): Ast.Obj {
 
 	const map = new Map<string, Ast.Expression>();
 	while (!s.is(TokenKind.CloseBrace)) {
+		const startPos = s.getPos();
+
+		const isIdentifierKey = s.is(TokenKind.Identifier);
 		const k = parseObjectKey(s);
 		if (map.has(k)) {
 			throw new AiScriptSyntaxError(`Key ${k} is duplicated.`, s.getPos());
 		}
 		s.next();
 
-		s.expect(TokenKind.Colon);
-		s.next();
+		let v: Ast.Expression;
 
-		const v = parseExpr(s, isStatic);
+		if (!isIdentifierKey || isStatic) s.expect(TokenKind.Colon);
+		if (s.is(TokenKind.Colon)) {
+			s.next();
+
+			v = parseExpr(s, isStatic);
+		} else {
+			v = NODE('identifier', { name: k }, startPos, s.getPos());
+		}
 
 		map.set(k, v);
 

test/aison.ts

@@ -62,6 +62,10 @@ greet()`)).toThrow();
 		expect(() => AiSON.parse('{key: (3 + 5)}')).toThrow();
 	});
 
+	test.concurrent('not allowed: object shorthand', () => {
+		expect(() => AiSON.parse('{key}')).toThrow();
+	});
+
 	test.concurrent('not allowed: labeled expression', () => {
 		expect(() => AiSON.parse('#label: eval { 1 }')).toThrow();
 	});

test/literals.ts

@@ -243,6 +243,26 @@ describe('literal', () => {
 		});
 	});
 
+	test.concurrent('obj (shorthand)', async () => {
+		const res = await exe(`
+		let a = 1
+		<: { a }
+		`);
+		eq(res, OBJ(new Map([['a', NUM(1)]])));
+	});
+
+	test.concurrent('obj (reserved word as shorthand)', async () => {
+		await expect(() => exe(`
+			<: { exists }
+		`)).rejects.toThrow(AiScriptSyntaxError);
+	});
+
+	test.concurrent('obj (string as shorthand)', async () => {
+		await expect(() => exe(`
+			<: { "hoge" }
+		`)).rejects.toThrow(AiScriptSyntaxError);
+	});
+
 	test.concurrent('obj (escaped reserved word as key)', async () => {
 		await expect(async () => await exe(`
 		<: {

test/syntax.ts

@@ -635,6 +635,13 @@ describe('Variable declaration', () => {
 		`);
 		eq(res, ARR([NUM(1), NUM(2)]));
 	});
+	test.concurrent('destructuring declaration with shorthand', async () => {
+		const res = await exe(`
+			let { value } = { value: 1 }
+			<: value
+		`);
+		eq(res, NUM(1));
+	});
 	test.concurrent('empty function', async () => {
 		const res = await exe(`
 			@hoge() { }

unreleased/obj-shorthand-sugar-syntax.md

@@ -0,0 +1,2 @@
+- オブジェクトリテラルとオブジェクトの分割代入構文内で、キーと同名の変数を参照する省略記法を使用できるようになりました。
+	- 例えば`{ hoge }`は`{ hoge: hoge }`と等価です。