Inserted string validation as separate task in compiler.

frog/leg/warnings.dart

Index: frog/leg/warnings.dart
diff --git a/frog/leg/warnings.dart b/frog/leg/warnings.dart
index e0e02c9d62a43a8ee845d4f9d2ed9a3d6b3a03bf..25aa8840ce199e6ef2eb45335d0e2118def830d0 100644
--- a/frog/leg/warnings.dart
+++ b/frog/leg/warnings.dart
@@ -86,6 +86,14 @@ class MessageKind {
   static final NOT_A_COMPILE_TIME_CONSTANT = const MessageKind(
       '#{1} cannot be used as compile-time constant');
 
+  static final INVALID_STRING_ESCAPE = const MessageKind(
+      'Unexpected character or end-of-string in string escape at index #{1}');

[ahe, 2012/01/25 08:39:44]

I'm not a big fan of telling the user: I'm not sure what happened, but it was
either this or that. So if you think it is important to distinguish between
"unexpected character" and "end-of-string" (I don't ;-), please make two error
codes. But I'd just write:

"unexpected character in string escape"

[ahe, 2012/01/25 08:39:44]

"Unexpected" should be lowercase to be consistent with other messages (except
the inconsistent ones :-)

[ahe, 2012/01/25 08:39:44]

" at index #{1}" should be removed. Instead this position should be reported by
the diagnostic system.

[Lasse Reichstein Nielsen, 2012/01/26 10:14:20]

I'm removing all of these, since I'm not using them any more.

+  static final INVALID_SINGLE_LINE_STRING = const MessageKind(
+      'Line terminator in single-line string at index #{1}');

[ahe, 2012/01/25 08:39:44]

Lowercase and remove "at index #{1}".

+  static final INVALID_UNICODE_SCALAR = const MessageKind(
+      'Invalid character U+#{2} in string escape at index #{1}');

[ahe, 2012/01/25 08:39:44]

Lowercase and remove "at index #{1}".

+
+
   toString() => template;
 }