Report compile-time errors on cyclic hierarchies.

pkg/front_end/lib/src/fasta/builder/class_builder.dart

Index: pkg/front_end/lib/src/fasta/builder/class_builder.dart
diff --git a/pkg/front_end/lib/src/fasta/builder/class_builder.dart b/pkg/front_end/lib/src/fasta/builder/class_builder.dart
index 113222635c94ebf01a28097817733aa3541ae6ee..41273c323baaa696f07dadd01bd724dc31e3b860 100644
--- a/pkg/front_end/lib/src/fasta/builder/class_builder.dart
+++ b/pkg/front_end/lib/src/fasta/builder/class_builder.dart
@@ -187,4 +187,16 @@ abstract class ClassBuilder<T extends TypeBuilder, R>
     }
     return substitutionMap;
   }
+
+  void addCompileTimeError(int charOffset, String message) {
+    library.addCompileTimeError(charOffset, message, fileUri: fileUri);
+  }
+
+  void addWarning(int charOffset, String message) {
+    library.addWarning(charOffset, message, fileUri: fileUri);
+  }
+
+  void addNit(int charOffset, String message) {
+    library.addNit(charOffset, message, fileUri: fileUri);

[Paul Berry, 2017/03/22 16:22:30]

Not a blocking issue for this CL, but when we next meet I'd like to understand
what a "nit" is.  We've been hearing reports for quite some time that users are
confused by the subtle distinctions analyzer makes among error, warning, hint,
and lint, and we've been wanting to reduce the number of categories.  Adding a
"nit" category seems like it goes against this goal.

[ahe, 2017/03/22 17:49:49]

I agree. I use "nit" to report warnings that aren't warnings. Perhaps I should
silence them unless using verbose mode.

[ahe, 2017/03/23 11:35:35]

I did that in CL 2770683005.

+  }
 }