Allow constants as field initial values as well as creation thunks

lib/protobuf.dart

Index: lib/protobuf.dart
diff --git a/lib/protobuf.dart b/lib/protobuf.dart
index f1e55cd21534cb6604e5d7a8a2d2a4e76460a555..13bddf0c772e5407cc2af7e4df35c1fb95abf27f 100644
--- a/lib/protobuf.dart
+++ b/lib/protobuf.dart
@@ -26,6 +26,15 @@ part 'src/protobuf/unknown_field_set.dart';
 part 'src/protobuf/utils.dart';
 part 'src/protobuf/wire_format.dart';
 
+// TODO(sra): Remove this method when clients upgrade to protoc 0.3.5

[Siggi Cherem (dart-lang), 2014/12/19 21:53:37]

add @deprecated.

Alternatively, you can bump this as a breaking change (0.4.0) and require it in
protoc 0.3.5.

People should then be protected by the fact that the version increase was a
breaking change. If we fear that some people depend on protobuflib transitively
(they shouldn't but some people might), then we can make it a breaking change in
protoc as well.

[sra1, 2014/12/19 23:15:54]

This CL can land ahead of the protoc one.
I don't think it should me marked as deprecated until I land protoc 0.3.5
There is not much a user can do about the use of deprecated functions in
generated code.

 Int64 makeLongInt(int n) => new Int64(n);
 
+// TODO(http://dartbug.com/21915): Use Int64.parse() when available.

[Siggi Cherem (dart-lang), 2014/12/19 21:53:38]

nit: format the todo with your username, as follows:

// TODO(sra): Use .... See dartbug.com/21915

[sra1, 2014/12/19 23:15:54]

Done.

+Int64 parseLongInt(String text) {
+  if (text.startsWith('0x')) return Int64.parseHex(text.substring(2));
+  if (text.startsWith('+0x')) return Int64.parseHex(text.substring(3));
+  if (text.startsWith('-0x')) return -Int64.parseHex(text.substring(3));
+  return Int64.parseInt(text);
+}
+
 const _UTF8 = const Utf8Codec(allowMalformed: true);