Complain about cyclic typedefs.

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

Index: pkg/front_end/lib/src/fasta/kernel/kernel_function_type_alias_builder.dart
diff --git a/pkg/front_end/lib/src/fasta/kernel/kernel_function_type_alias_builder.dart b/pkg/front_end/lib/src/fasta/kernel/kernel_function_type_alias_builder.dart
index a4f614ff31f2db8fb06e63c43d7a787b10210300..1d3c0dbe59ce66950dcc499a772c29d79ee4f80f 100644
--- a/pkg/front_end/lib/src/fasta/kernel/kernel_function_type_alias_builder.dart
+++ b/pkg/front_end/lib/src/fasta/kernel/kernel_function_type_alias_builder.dart
@@ -15,7 +15,6 @@ import 'package:kernel/ast.dart'
 
 import 'package:kernel/type_algebra.dart' show substitute;
 
-import '../messages.dart' show warning;
 import 'kernel_builder.dart'
     show
         FormalParameterBuilder,
@@ -58,9 +57,8 @@ class KernelFunctionTypeAliasBuilder
     if (thisType != null) {
       if (thisType == const InvalidType()) {
         thisType = const DynamicType();
-        // TODO(ahe): Build an error somehow.
-        warning(
-            parent.uri, -1, "The typedef '$name' has a reference to itself.");
+        library.addCompileTimeError(
+            charOffset, "The typedef '$name' has a reference to itself.");
       }
       return thisType;
     }