Add String.replaceFirstMapped.

sdk/lib/_internal/compiler/js_lib/string_helper.dart

Index: sdk/lib/_internal/compiler/js_lib/string_helper.dart
diff --git a/sdk/lib/_internal/compiler/js_lib/string_helper.dart b/sdk/lib/_internal/compiler/js_lib/string_helper.dart
index ff2505729a1b3cce8352be876681941925776479..6032d9f1f95f367e600030a25403131670d273ba 100644
--- a/sdk/lib/_internal/compiler/js_lib/string_helper.dart
+++ b/sdk/lib/_internal/compiler/js_lib/string_helper.dart
@@ -193,21 +193,34 @@ stringReplaceAllStringFuncUnchecked(receiver, pattern, onMatch, onNonMatch) {
 }
 
 
-stringReplaceFirstUnchecked(receiver, from, to, [int startIndex = 0]) {
+stringReplaceFirstUnchecked(receiver, from, to, int startIndex) {
   if (from is String) {
     var index = receiver.indexOf(from, startIndex);

[floitsch, 2015/02/11 11:49:14]

we are missing types here... (and in your code).

[Lasse Reichstein Nielsen, 2015/02/12 09:17:16]

Added.
You are also missing types on all the function signatures, so I assumed it was
deliberate.

     if (index < 0) return receiver;
     return '${receiver.substring(0, index)}$to'
            '${receiver.substring(index + from.length)}';
-  } else if (from is JSSyntaxRegExp) {
+  }
+  if (from is JSSyntaxRegExp) {
     return startIndex == 0 ?
         stringReplaceJS(receiver, regExpGetNative(from), to) :
         stringReplaceFirstRE(receiver, from, to, startIndex);
-  } else {
-    checkNull(from);
-    // TODO(floitsch): implement generic String.replace (with patterns).
-    throw "String.replace(Pattern) UNIMPLEMENTED";
   }
+  checkNull(from);
+  var matches = from.allMatches(receiver, startIndex).iterator;
+  if (!matches.moveNext()) return receiver;
+  var match = matches.current;
+  return '${receiver.substring(0, match.start)}$to'
+         '${receiver.substring(match.end)}';
+}
+
+stringReplaceFirstMappedUnchecked(receiver, from, replace,
+                                  int startIndex) {
+  var matches = from.allMatches(receiver, startIndex).iterator;
+  if (!matches.moveNext()) return receiver;
+  var match = matches.current;
+  var replacement = "${replace(match)}";
+  return '${receiver.substring(0, match.start)}$replacement'
+         '${receiver.substring(match.end)}';
 }
 
 stringJoinUnchecked(array, separator) {