if式やmatch式、for文が文1つでもスコープを生成するように (#827)

src/interpreter/index.ts

@@ -4,6 +4,7 @@
 
 import { autobind } from '../utils/mini-autobind.js';
 import { AiScriptError, NonAiScriptError, AiScriptNamespaceError, AiScriptIndexOutOfRangeError, AiScriptRuntimeError, AiScriptHostsideError } from '../error.js';
+import * as Ast from '../node.js';
 import { Scope } from './scope.js';
 import { std } from './lib/std.js';
 import { assertNumber, assertString, assertFunction, assertBoolean, assertObject, assertArray, eq, isObject, isArray, expectAny, reprValue } from './util.js';
@@ -12,7 +13,6 @@ import { getPrimProp } from './primitive-props.js';
 import { Variable } from './variable.js';
 import type { JsValue } from './util.js';
 import type { Value, VFn } from './value.js';
-import type * as Ast from '../node.js';
 
 export type LogObject = {
 	scope?: string;
@@ -266,6 +266,11 @@ export class Interpreter {
 		}
 	}
 
+	@autobind
+	private _evalClause(node: Ast.Statement | Ast.Expression, scope: Scope): Promise<Value> {
+		return this._eval(node, Ast.isStatement(node) ? scope.createChildScope() : scope);
+	}
+
 	@autobind
 	private _eval(node: Ast.Node, scope: Scope): Promise<Value> {
 		return this.__eval(node, scope).catch(e => {
@@ -303,21 +308,21 @@ export class Interpreter {
 				const cond = await this._eval(node.cond, scope);
 				assertBoolean(cond);
 				if (cond.value) {
-					return this._eval(node.then, scope);
+					return this._evalClause(node.then, scope);
 				} else {
 					if (node.elseif && node.elseif.length > 0) {
 						for (const elseif of node.elseif) {
 							const cond = await this._eval(elseif.cond, scope);
 							assertBoolean(cond);
 							if (cond.value) {
-								return this._eval(elseif.then, scope);
+								return this._evalClause(elseif.then, scope);
 							}
 						}
 						if (node.else) {
 							return this._eval(node.else, scope);
 						}
 					} else if (node.else) {
-						return this._eval(node.else, scope);
+						return this._evalClause(node.else, scope);
 					}
 				}
 				return NULL;
@@ -328,11 +333,11 @@ export class Interpreter {
 				for (const qa of node.qs) {
 					const q = await this._eval(qa.q, scope);
 					if (eq(about, q)) {
-						return await this._eval(qa.a, scope);
+						return await this._evalClause(qa.a, scope);
 					}
 				}
 				if (node.default) {
-					return await this._eval(node.default, scope);
+					return await this._evalClause(node.default, scope);
 				}
 				return NULL;
 			}
@@ -355,7 +360,7 @@ export class Interpreter {
 					const times = await this._eval(node.times, scope);
 					assertNumber(times);
 					for (let i = 0; i < times.value; i++) {
-						const v = await this._eval(node.for, scope);
+						const v = await this._evalClause(node.for, scope);
 						if (v.type === 'break') {
 							break;
 						} else if (v.type === 'return') {

test/syntax.ts

@@ -743,6 +743,15 @@ describe('for', () => {
 		}
 		assert.fail();
 	});
+
+	test.concurrent('scope', async () => {
+		await assert.rejects(async () => {
+			await exe(`
+			for 1 let a = 1
+			<: a
+			`);
+		});
+	});
 });
 
 describe('each', () => {
@@ -1478,6 +1487,27 @@ describe('if', () => {
 		`);
 		eq(res2, STR('kawaii'));
 	});
+
+	test.concurrent('scope', async () => {
+		await assert.rejects(async () => {
+			await exe(`
+			if true let a = 1
+			<: a
+			`);
+		});
+		await assert.rejects(async () => {
+			await exe(`
+			if false null elif true let a = 1
+			<: a
+			`);
+		});
+		await assert.rejects(async () => {
+			await exe(`
+			if false null else let a = 1
+			<: a
+			`);
+		});
+	});
 });
 
 describe('eval', () => {
@@ -1559,6 +1589,21 @@ describe('match', () => {
 		`);
 		eq(res, STR('ai'));
 	});
+
+	test.concurrent('scope', async () => {
+		await assert.rejects(async () => {
+			await exe(`
+			match 1 { case 1 => let a = 1 }
+			<: a
+			`);
+		});
+		await assert.rejects(async () => {
+			await exe(`
+			match 1 { default => let a = 1 }
+			<: a
+			`);
+		});
+	});
 });
 
 describe('exists', () => {

unreleased/single-statement-clause-scope.md

@@ -0,0 +1 @@
+- **Breaking Change** if式やmatch式、for文の内容が1つの文である場合にもスコープが生成されるようになりました。これらの構文内で定義された変数は外部から参照できなくなります。