Fix escape sequence

Author: imteekay

src/check.ts

@@ -54,7 +54,9 @@ export function check(module: Module) {
         error(expression.pos, 'Could not resolve ' + expression.text);
         return errorType;
       case Node.Literal:
-        return typeof expression.value === 'string' ? stringType : numberType;
+        return numberType;
+      case Node.StringLiteral:
+        return stringType;
       case Node.Assignment:
         const v = checkExpression(expression.value);
         const t = checkExpression(expression.name);

src/emit.ts

@@ -1,5 +1,22 @@
 import { Statement, Node, Expression } from './types';
 
+const singleQuoteRegex = /[\\\'\t\v\f\b\r\n]/g;
+const doubleQuoteRegex = /[\\\"\t\v\f\b\r\n]/g;
+
+const escapedCharsMap = new Map(
+  Object.entries({
+    '\t': '\\t',
+    '\v': '\\v',
+    '\f': '\\f',
+    '\b': '\\b',
+    '\r': '\\r',
+    '\n': '\\n',
+    '\\': '\\\\',
+    '"': '\\"',
+    "'": "\\'",
+  }),
+);
+
 export function emit(statements: Statement[]) {
   return statements.map(emitStatement).join(';\n');
 }
@@ -24,7 +41,22 @@ function emitExpression(expression: Expression): string {
       return expression.text;
     case Node.Literal:
       return '' + expression.value;
+    case Node.StringLiteral:
+      return expression.isSingleQuote
+        ? `'${escapeString(expression.value, true)}'`
+        : `"${escapeString(expression.value, false)}"`;
     case Node.Assignment:
       return `${expression.name.text} = ${emitExpression(expression.value)}`;
   }
 }
+
+function escapeString(string: string, isSingleQuote: boolean) {
+  return string.replace(
+    isSingleQuote ? singleQuoteRegex : doubleQuoteRegex,
+    replacement,
+  );
+}
+
+function replacement(char: string) {
+  return escapedCharsMap.get(char) || char;
+}

src/lex.ts

@@ -11,12 +11,14 @@ export function lex(s: string): Lexer {
   let pos = 0;
   let text = '';
   let token = Token.BOF;
+  let firstChar: string;
 
   return {
     scan,
     token: () => token,
     pos: () => pos,
     text: () => text,
+    isSingleQuote: () => firstChar === "'",
   };
 
   function scan() {
@@ -41,6 +43,7 @@ export function lex(s: string): Lexer {
           ? keywords[text as keyof typeof keywords]
           : Token.Identifier;
     } else if (['"', "'"].includes(s.charAt(pos))) {
+      firstChar = s.charAt(pos);
       text = scanString();
       token = Token.String;
     } else {
@@ -114,9 +117,11 @@ export function lex(s: string): Lexer {
       case CharCodes.r:
         return '\r';
       case CharCodes.singleQuote:
-        return "'";
+        // prettier-ignore
+        return "\'";
       case CharCodes.doubleQuote:
-        return '"';
+        // prettier-ignore
+        return '\"';
       default:
         return String.fromCharCode(char);
     }

src/parse.ts

@@ -37,7 +37,12 @@ export function parse(lexer: Lexer): Module {
     } else if (tryParseToken(Token.Literal)) {
       return { kind: Node.Literal, value: +lexer.text(), pos };
     } else if (tryParseToken(Token.String)) {
-      return { kind: Node.Literal, value: lexer.text(), pos };
+      return {
+        kind: Node.StringLiteral,
+        value: lexer.text(),
+        pos,
+        isSingleQuote: lexer.isSingleQuote(),
+      };
     }
     error(
       pos,

src/types.ts

@@ -21,6 +21,7 @@ export type Lexer = {
   token(): Token;
   pos(): number;
   text(): string;
+  isSingleQuote(): boolean;
 };
 
 export enum Node {
@@ -30,6 +31,7 @@ export enum Node {
   ExpressionStatement,
   Var,
   TypeAlias,
+  StringLiteral,
 }
 
 export type Error = {
@@ -41,7 +43,7 @@ export interface Location {
   pos: number;
 }
 
-export type Expression = Identifier | Literal | Assignment;
+export type Expression = Identifier | Literal | Assignment | StringLiteral;
 
 export type Identifier = Location & {
   kind: Node.Identifier;
@@ -50,7 +52,13 @@ export type Identifier = Location & {
 
 export type Literal = Location & {
   kind: Node.Literal;
-  value: number | string;
+  value: number;
+};
+
+export type StringLiteral = Location & {
+  kind: Node.StringLiteral;
+  value: string;
+  isSingleQuote: boolean;
 };
 
 export type Assignment = Location & {