Properly handle forwarding factory constructors in type inference.

sdk/lib/_internal/compiler/implementation/inferrer/simple_types_inferrer.dart

Index: sdk/lib/_internal/compiler/implementation/inferrer/simple_types_inferrer.dart
diff --git a/sdk/lib/_internal/compiler/implementation/inferrer/simple_types_inferrer.dart b/sdk/lib/_internal/compiler/implementation/inferrer/simple_types_inferrer.dart
index af97966c71e4d4fc0f784ae620b777ff1fe48c06..0008dd5dbf6f1521df87c8ec9be9f483fdf58bda 100644
--- a/sdk/lib/_internal/compiler/implementation/inferrer/simple_types_inferrer.dart
+++ b/sdk/lib/_internal/compiler/implementation/inferrer/simple_types_inferrer.dart
@@ -979,6 +979,15 @@ class SimpleTypeInferrerVisitor<T>
         analyzeSuperConstructorCall(element, arguments);
       }
     }
+    // If we are looking at a new expression on a forwarding factory,
+    // we have to forward the call to the effective target of the
+    // factory.
+    if (element.isFactoryConstructor) {
+      ConstructorElement constructor = element;
+      if (constructor.isRedirectingFactory) {
+        element = constructor.effectiveTarget.implementation;
+      }
+    }
     if (element.isForeign(compiler.backend)) {
       return handleForeignSend(node);
     }
@@ -1115,6 +1124,8 @@ class SimpleTypeInferrerVisitor<T>
                      Selector selector,
                      Element element,
                      ArgumentsTypes arguments) {
+    assert(!element.isFactoryConstructor ||
+           !(element as ConstructorElement).isRedirectingFactory);
     // Erroneous elements may be unresolved, for example missing getters.
     if (Elements.isUnresolved(element)) return types.dynamicType;
     // TODO(herhut): should we follow redirecting constructors here? We would