Implement parsing and resolving of type-variables.

frog/leg/warnings.dart

Index: frog/leg/warnings.dart
diff --git a/frog/leg/warnings.dart b/frog/leg/warnings.dart
index e18c221f23d0f838b014b061654fbc3497787b32..218dbf2349d95222b260f01c623d4528db45d5c3 100644
--- a/frog/leg/warnings.dart
+++ b/frog/leg/warnings.dart
@@ -116,6 +116,8 @@ class MessageKind {
       'unused label #{1}');
   static final INVALID_CONTINUE = const MessageKind(
       'target of continue is not a loop or switch case');
+  static final TYPE_VARIABLE_AS_CONSTRUCTOR = const MessageKind(
+      'cannot use type variable as constructor');
   static final INVALID_BREAK = const MessageKind(
       'target of break is not a statement');
   static final INVALID_USE_OF_SUPER = const MessageKind(
@@ -143,6 +145,10 @@ class MessageKind {
   static final NO_DEFAULT_CLASS = const MessageKind(
       "no default class on enclosing interface '#{1}'");
 
+  static final CYCLIC_TYPE_VARIABLE = const MessageKind(
+      "cyclic reference to type variable #{1}");
+  static final TYPE_NAME_EXPECTED = const MessageKind(
+      "class or interface name exptected");
   toString() => template;
 }