In constant evaluation, properly handle redirecting factory constructors.

editor/tools/plugins/com.google.dart.engine_test/src/com/google/dart/engine/resolver/CompileTimeErrorCodeTest.java

Index: editor/tools/plugins/com.google.dart.engine_test/src/com/google/dart/engine/resolver/CompileTimeErrorCodeTest.java
diff --git a/editor/tools/plugins/com.google.dart.engine_test/src/com/google/dart/engine/resolver/CompileTimeErrorCodeTest.java b/editor/tools/plugins/com.google.dart.engine_test/src/com/google/dart/engine/resolver/CompileTimeErrorCodeTest.java
index 5154738c5dd16af1502cb9ec4a471fe181bb1ade..ed8f62acf620d154eb67d4efe33a678467b3ff02 100644
--- a/editor/tools/plugins/com.google.dart.engine_test/src/com/google/dart/engine/resolver/CompileTimeErrorCodeTest.java
+++ b/editor/tools/plugins/com.google.dart.engine_test/src/com/google/dart/engine/resolver/CompileTimeErrorCodeTest.java
@@ -700,6 +700,24 @@ public class CompileTimeErrorCodeTest extends ResolverTestCase {
     verify(source);
   }
 
+  public void test_constMapKeyTypeImplementsEquals_factory() throws Exception {
+    Source source = addSource(createSource(//
+        "class A { const factory A() = B; }",
+        "",
+        "class B implements A {",
+        "  const B();",
+        "",
+        "  operator ==(o) => true;",
+        "}",
+        "",
+        "main() {",
+        "  var m = const { const A(): 42 };",
+        "}"));
+    resolve(source);
+    assertErrors(source, CompileTimeErrorCode.CONST_MAP_KEY_EXPRESSION_TYPE_IMPLEMENTS_EQUALS);
+    verify(source);
+  }
+
   public void test_constMapKeyTypeImplementsEquals_super() throws Exception {
     Source source = addSource(createSource(//
         "class A {",