Check const constructors.

pkg/front_end/lib/src/fasta/source/diet_listener.dart

Index: pkg/front_end/lib/src/fasta/source/diet_listener.dart
diff --git a/pkg/front_end/lib/src/fasta/source/diet_listener.dart b/pkg/front_end/lib/src/fasta/source/diet_listener.dart
index 11e4cd8d1f49f6bd7c7ab8e38ff2af425147a572..fd3603bd7101f40e86326873eb902260de8e2e36 100644
--- a/pkg/front_end/lib/src/fasta/source/diet_listener.dart
+++ b/pkg/front_end/lib/src/fasta/source/diet_listener.dart
@@ -385,7 +385,8 @@ class DietListener extends StackListener {
       MemberBuilder builder, Scope memberScope, bool isInstanceMember,
       [Scope formalParameterScope]) {
     return new BodyBuilder(library, builder, memberScope, formalParameterScope,
-        hierarchy, coreTypes, currentClass, isInstanceMember, uri);
+        hierarchy, coreTypes, currentClass, isInstanceMember, uri)
+      ..constantExpressionRequired = builder.isConstructor && builder.isConst;
   }
 
   void buildFunctionBody(Token token, ProcedureBuilder builder) {