Perform type inference on explicitly typed fields.

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 d8ebbd10e9fce164d15e84b1df4b5bf536a1fc6c..a5efbc240083ed52a1021824b5fba8b950824e25 100644
--- a/pkg/front_end/lib/src/fasta/kernel/body_builder.dart
+++ b/pkg/front_end/lib/src/fasta/kernel/body_builder.dart
@@ -366,6 +366,7 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
               "Unhandled: '${field.name}' has more than one declaration.");
         }
         field.initializer = initializer;
+        _typeInferrer.inferFieldInitializer(field.builtType, initializer);
       }
     }
     pop(); // Type.