Change the calling conventions for handleUnrecoverableError.

pkg/front_end/lib/src/fasta/kernel/body_builder.dart

Index: pkg/front_end/lib/src/fasta/kernel/body_builder.dart
diff --git a/pkg/front_end/lib/src/fasta/kernel/body_builder.dart b/pkg/front_end/lib/src/fasta/kernel/body_builder.dart
index afcabb0fc779ff76d2fb69b8955a7aab78951566..8fd4ef7f892cf4a5a473e0c83c5db56f13e5b104 100644
--- a/pkg/front_end/lib/src/fasta/kernel/body_builder.dart
+++ b/pkg/front_end/lib/src/fasta/kernel/body_builder.dart
@@ -2191,7 +2191,7 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
   Token handleUnrecoverableError(Token token, ErrorKind kind, Map arguments) {
     if (isDartLibrary && kind == ErrorKind.ExpectedFunctionBody) {
       Token recover = skipNativeClause(token);
-      if (recover != null) return recover;
+      if (recover != null) return newSyntheticToken(recover);

[ahe, 2017/03/09 12:08:39]

I think we should modify skipNativeClause instead.

[Paul Berry, 2017/03/09 21:51:21]

Done.

     } else if (kind == ErrorKind.UnexpectedToken) {
       String expected = arguments["expected"];
       const List<String> trailing = const <String>[")", "}", ";", ","];
@@ -2199,7 +2199,7 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
         arguments.putIfAbsent("actual", () => token.value);
         handleRecoverableError(token, ErrorKind.ExpectedButGot, arguments);
       }
-      return token;
+      return newSyntheticToken(token);

[ahe, 2017/03/09 12:08:39]

FYI: Expect an easy conflict here. The return statement should be in the
then-block.

[Paul Berry, 2017/03/09 21:51:21]

Thanks for the heads up.

     }
     return super.handleUnrecoverableError(token, kind, arguments);
   }