Patch signatures checked in resolver.

lib/compiler/implementation/warnings.dart

Index: lib/compiler/implementation/warnings.dart
diff --git a/lib/compiler/implementation/warnings.dart b/lib/compiler/implementation/warnings.dart
index 5e3f40f31b06a5ebe69bb7f9d70667b5fdde455c..8036c2d62043232d9fabe8896a4db6f3e14f8790 100644
--- a/lib/compiler/implementation/warnings.dart
+++ b/lib/compiler/implementation/warnings.dart
@@ -264,6 +264,25 @@ Invalid offset (#{1}) in source map.
 File: #{2}
 Length: #{3}''');
 
+  static const PATCH_RETURN_TYPE_MISMATCH = const MessageKind(
+      "Patch return type '#{3}' doesn't match '#{2}' on origin method '#{1}'.");
+
+  static const PATCH_REQUIRED_PARAMETER_COUNT_MISMATCH = const MessageKind(
+      "Required parameter count of patch method (#{3}) doesn't match parameter "
+      "count on origin method '#{1}' (#{2}).");
+
+  static const PATCH_OPTIONAL_PARAMETER_COUNT_MISMATCH = const MessageKind(
+      "Optional parameter count of patch method (#{3}) doesn't match parameter "
+      "count on origin method '#{1}' (#{2}).");
+
+  static const PATCH_OPTIONAL_PARAMETER_NAMED_MISMATCH = const MessageKind(
+      "Optional parameters of origin and patch method '#{1}' must "
+      "both be either named or positional.");
+
+  static const PATCH_PARAMETER_MISMATCH = const MessageKind(
+      "Patch method parameter '#{3}' doesn't match '#{2}' on origin method "
+      "#{1}.");
+
   static const COMPILER_CRASHED = const MessageKind(
       "Error: The compiler crashed when compiling this element.");