Prepare for separate setter scope.

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

Index: pkg/front_end/lib/src/fasta/builder/constructor_reference_builder.dart
diff --git a/pkg/front_end/lib/src/fasta/builder/constructor_reference_builder.dart b/pkg/front_end/lib/src/fasta/builder/constructor_reference_builder.dart
index 96ae8890daf9b2470c5b75e2bf18b8363cd0c8ba..881b5b33b3d32a612b29d8457a4d439bab1becab 100644
--- a/pkg/front_end/lib/src/fasta/builder/constructor_reference_builder.dart
+++ b/pkg/front_end/lib/src/fasta/builder/constructor_reference_builder.dart
@@ -36,10 +36,10 @@ class ConstructorReferenceBuilder extends Builder {
       builder = scope.lookup(prefix, charOffset, fileUri);
       if (builder is PrefixBuilder) {
         PrefixBuilder prefix = builder;
-        builder = prefix.exports[middle];
+        builder = prefix.lookup(middle, charOffset, fileUri);
       } else if (builder is ClassBuilder) {
         ClassBuilder cls = builder;
-        builder = cls.constructors[middle];
+        builder = cls.findConstructorOrFactory(middle, charOffset, fileUri);
         if (suffix == null) {
           target = builder;
           return;
@@ -47,10 +47,12 @@ class ConstructorReferenceBuilder extends Builder {
       }
     }
     if (builder is ClassBuilder) {
-      target = builder.constructors[suffix ?? ""];
+      target =
+          builder.findConstructorOrFactory(suffix ?? "", charOffset, fileUri);
     }
     if (target == null) {
-      warning(null, -1, "Couldn't find constructor '$fullNameForErrors'.");
+      warning(fileUri, charOffset,
+          "Couldn't find constructor '$fullNameForErrors'.");
     }
   }
 }