Reduce strong mode errors and warnings

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

Index: pkg/front_end/lib/src/fasta/kernel/kernel_enum_builder.dart
diff --git a/pkg/front_end/lib/src/fasta/kernel/kernel_enum_builder.dart b/pkg/front_end/lib/src/fasta/kernel/kernel_enum_builder.dart
index 851c4563e4c8d55f155f8ff96119c15a2a2a7082..acf90c7dc7b90e64ee95441565078853a5df6af9 100644
--- a/pkg/front_end/lib/src/fasta/kernel/kernel_enum_builder.dart
+++ b/pkg/front_end/lib/src/fasta/kernel/kernel_enum_builder.dart
@@ -136,8 +136,9 @@ class KernelEnumBuilder extends SourceClassBuilder
     KernelEnumBuilder enumBuilder = new KernelEnumBuilder.internal(metadata,
         name, members, types, cls, constants, toStringMap, intType, stringType,
         parent);
-    members.forEach((String name, MemberBuilder builder) {
-      builder.parent = enumBuilder;
+    members.forEach((String name, Builder builder) {

[Siggi Cherem (dart-lang), 2017/02/02 04:26:58]

it would be nice to be able to use `covariant` in this context too.

[ahe, 2017/02/02 07:28:30]

Please don't change explicit types.

[Siggi Cherem (dart-lang), 2017/02/06 23:35:50]

OK - I switched it to dynamic (I believe this is what you suggested, but please
correct me if this is wrong)

+      MemberBuilder memberBuilder = builder;
+      memberBuilder.parent = enumBuilder;
     });
     selfType.builder = enumBuilder;
     return enumBuilder;