enhance: エスケープシーケンスの追加

src/parser/scanner.ts

@@ -1,5 +1,5 @@
 import { AiScriptSyntaxError, AiScriptUnexpectedEOFError } from '../error.js';
-import { decodeUnicodeEscapeSequence } from '../utils/characters.js';
+import { decodeUnicodeEscapeSequence, tryDecodeSingleEscapeCharacter } from '../utils/characters.js';
 import { CharStream } from './streams/char-stream.js';
 import { TOKEN, TokenKind } from './token.js';
 import { unexpectedTokenError } from './utils.js';
@@ -463,6 +463,25 @@ export class Scanner implements ITokenStream {
 		return;
 	}
 
+	private decodeEscapeSequence(): string {
+		if (this.stream.eof) {
+			throw new AiScriptUnexpectedEOFError(this.stream.getPos());
+		}
+
+		if (this.stream.char === 'u') {
+			const unicodeEscapeSequence = this.readUnicodeEscapeSequence();
+			return String.fromCharCode(Number.parseInt(unicodeEscapeSequence.slice(1), 16));
+		}
+
+		const decodedSingleEscapeCharacter = tryDecodeSingleEscapeCharacter(this.stream.char);
+		if (decodedSingleEscapeCharacter != null) {
+			this.stream.next();
+			return decodedSingleEscapeCharacter;
+		}
+
+		throw new AiScriptSyntaxError(`invalid escape character: "${this.stream.char}"`, this.stream.getPos());
+	}
+
 	private readUnicodeEscapeSequence(): `u${string}` {
 		if (this.stream.eof || (this.stream.char as string) !== 'u') {
 			throw new AiScriptSyntaxError('character "u" expected', this.stream.getPos());
@@ -569,11 +588,7 @@ export class Scanner implements ITokenStream {
 					break;
 				}
 				case 'escape': {
-					if (this.stream.eof) {
-						throw new AiScriptUnexpectedEOFError(pos);
-					}
-					value += this.stream.char;
-					this.stream.next();
+					value += this.decodeEscapeSequence();
 					state = 'string';
 					break;
 				}
@@ -632,13 +647,7 @@ export class Scanner implements ITokenStream {
 					break;
 				}
 				case 'escape': {
-					// エスケープ対象の文字が無いままEOFに達した
-					if (this.stream.eof) {
-						throw new AiScriptUnexpectedEOFError(pos);
-					}
-					// 普通の文字として取り込み
-					buf += this.stream.char;
-					this.stream.next();
+					buf += this.decodeEscapeSequence();
 					// 通常の文字列に戻る
 					state = 'string';
 					break;

src/utils/characters.ts

@@ -72,3 +72,21 @@ export function decodeUnicodeEscapeSequence(string: string): string {
 
 	return result;
 }
+
+export function tryDecodeSingleEscapeCharacter(s: string): string | null {
+	switch (s) {
+		// case 'b': return '\b';
+		case 't': return '\t';
+		case 'n': return '\n';
+		// case 'v': return '\v';
+		// case 'f': return '\f';
+		case 'r': return '\r';
+		case '"': return '"';
+		case '\'': return '\'';
+		case '\\': return '\\';
+		case '`': return '`';
+		case '{': return '{';
+		case '}': return '}';
+		default: return null;
+	}
+}

test/literals.ts

@@ -341,3 +341,83 @@ describe('Template syntax', () => {
 	});
 });
 
+describe('Escape sequence', () => {
+	describe('valid', () => {
+		const cases: [string, string][] = [
+			['\\t', '\t'],  // horizontal tab
+			['\\n', '\n'],  // line feed
+			['\\r', '\r'],  // carriage return
+			['\\"', '"'],
+			['\\\'', '\''],
+			['\\\\', '\\'],
+			['\\`', '`'],
+			['\\{', '{'],
+			['\\}', '}'],
+			['\\u0041', 'A'],
+			['\\u85cd', '藍'],
+			['\\u85CD', '藍'],
+			['\\ud842\\udfb7', '𠮷'],
+			['\\uD842\\uDFB7', '𠮷'],
+		];
+
+		describe('double quote', () => {
+			test.each(cases)('value of escape sequence "%s" must be "%s"', async (char, expected) => {
+				const res = await exe(`
+				<: "${char}"
+				`);
+				eq(res, STR(expected));
+			});
+		});
+
+		describe('single quote', () => {
+			test.each(cases)('value of escape sequence "%s" must be "%s"', async (char, expected) => {
+				const res = await exe(`
+				<: '${char}'
+				`);
+				eq(res, STR(expected));
+			});
+		});
+
+		describe('template', () => {
+			test.each(cases)('value of escape sequence "%s" must be "%s"', async (string, expected) => {
+				const res = await exe(`
+				<: \`${string}\`
+				`);
+				eq(res, STR(expected));
+			});
+		});
+	});
+
+	describe('invalid', () => {
+		const cases: [string][] = [
+			['\\x'],
+			['\\b'],
+			['\\v'],
+			['\\f'],
+		];
+
+		describe('double quote', () => {
+			test.each(cases)('value of escape sequence "%s" must not be allowed', async (char) => {
+				await expect(async () => await exe(`
+				<: "${char}"
+				`)).rejects.toThrow(AiScriptSyntaxError);
+			});
+		});
+
+		describe('single quote', () => {
+			test.each(cases)('value of escape sequence "%s" must not be allowed', async (char) => {
+				await expect(async () => await exe(`
+				<: '${char}'
+				`)).rejects.toThrow(AiScriptSyntaxError);
+			});
+		});
+
+		describe('template', () => {
+			test.each(cases)('value of escape sequence "%s" must not be allowed', async (string) => {
+				await expect(async () => await exe(`
+				<: \`${string}\`
+				`)).rejects.toThrow(AiScriptSyntaxError);
+			});
+		});
+	});
+});

unreleased/str_escape_sequnece.md

@@ -0,0 +1,8 @@
+- **Breaking change** 文字列リテラルやテンプレートリテラルにおけるエスケープシーケンスの仕様を変更しました。
+	- 以下のエスケープシーケンスが追加されました。
+		- `\t` - 水平タブ (U+0009)
+		- `\n` - 改行 (U+000A)
+		- `\r` - 復帰 (U+000D)
+		- `\u`とそれに続く4桁の16進数の英数字 - 与えられた値を持つUTF-16コード単位として解釈されます。
+		- `\"`, `\'`, `` \` ``, `\{`, `\}` - それぞれ、`\`の直後の文字そのものとなります。
+	- `\`とそれに続く文字列が上記のいずれにも一致しない場合、文法エラーが発生するようになりました。