Refactoring of string literals. Implement static string addition.

frog/leg/string_validator.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 // Check the validity of string literals.
 
 #library("stringvalidator");
 
 #import("leg.dart");
 #import("scanner/scannerlib.dart");
 #import("tree/tree.dart");
 #import("elements/elements.dart");
 #import("util/characters.dart");
 
 class StringValidator  {
   final DiagnosticListener listener;
 
   StringValidator(this.listener);
 
-  QuotedString validateQuotedString(Token token) {
+  DartString validateQuotedString(Token token) {
     SourceString source = token.value;
     StringQuoting quoting = quotingFromString(source);
     int leftQuote = quoting.leftQuoteLength;
     int rightQuote = quoting.rightQuoteLength;
     SourceString content = source.copyWithoutQuotes(leftQuote, rightQuote);
     return validateString(token,
                           token.charOffset + leftQuote,
                           content,
                           quoting);
   }
 
-  QuotedString validateInterpolationPart(Token token, StringQuoting quoting,
-                                         [bool isFirst = false,
-                                          bool isLast = false]) {
+  DartString validateInterpolationPart(Token token, StringQuoting quoting,
+                                       [bool isFirst = false,
+                                        bool isLast = false]) {
     SourceString source = token.value;
     int leftQuote = 0;
     int rightQuote = 0;
     if (isFirst) leftQuote = quoting.leftQuoteLength;
     if (isLast) rightQuote = quoting.rightQuoteLength;
     SourceString content = source.copyWithoutQuotes(leftQuote, rightQuote);
     return validateString(token,
                           token.charOffset + leftQuote,
                           content,
                           quoting);
@@ skipping 18 matching lines @@
     }
     return StringQuoting.get(quoteChar, raw, multiline);
   }
 
   void stringParseError(String message, Token token, int offset) {
     listener.cancel("$message @ $offset", token : token);
   }
 
   /**
    * Validates the escape sequences and special characters of a string literal.
-   * Returns a QuotedString if valid, and null if not.
+   * Returns a DartString if valid, and null if not.
    */
-  QuotedString validateString(Token token,
-                              int startOffset,
-                              SourceString string,
-                              StringQuoting quoting) {
+  DartString validateString(Token token,
+                            int startOffset,
+                            SourceString string,
+                            StringQuoting quoting) {
     // We only need to check for invalid x and u escapes, for line
     // terminators in non-multiline strings, and for invalid Unicode
     // scalar values (either directly or as u-escape values).
     int length = 0;
     int index = startOffset;
+    bool containsEscape = false;
     for(Iterator<int> iter = string.iterator(); iter.hasNext(); length++) {
       index++;
       int code = iter.next();
       if (code === $BACKSLASH) {
         if (quoting.raw) continue;
+        containsEscape = true;
         if (!iter.hasNext()) {
           stringParseError("Incomplete escape sequence",token, index);
           return null;
         }
         index++;
         code = iter.next();
         if (code === $x) {
           for (int i = 0; i < 2; i++) {
             if (!iter.hasNext()) {
               stringParseError("Incomplete escape sequence", token, index);
@@ skipping 56 matching lines @@
       // This handles both unescaped characters and the value of unicode
       // escapes.
       if (!isUnicodeScalarValue(code)) {
         stringParseError(
             "Invalid Unicode scalar value U+${code.toRadixString(16)}",
             token, index);
         return null;
       }
     }
     // String literal successfully validated.
-    return new QuotedString(string, quoting, length);
+    if (quoting.raw || !containsEscape) {
+      // A string without escapes could just as well have been raw.
+      return new DartString.rawString(string, length);
+    }
+    return new DartString.escapedString(string, length);
   }
 }