Small fixes to top level type inference.

pkg/front_end/lib/src/fasta/type_inference/type_inferrer.dart

 // Copyright (c) 2017, the Dart project authors. Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE.md file.
 
 import 'package:front_end/src/base/instrumentation.dart';
 import 'package:front_end/src/fasta/errors.dart' show internalError;
 import 'package:front_end/src/fasta/kernel/kernel_shadow_ast.dart';
 import 'package:front_end/src/fasta/names.dart' show callName;
 import 'package:front_end/src/fasta/type_inference/type_inference_engine.dart';
 import 'package:front_end/src/fasta/type_inference/type_inference_listener.dart';
@@ skipping 573 matching lines @@
       substitution =
           Substitution.fromPairs(calleeTypeParameters, explicitTypeArguments);
     } else if (calleeTypeParameters.length != 0) {
       substitution = Substitution.fromPairs(
           calleeTypeParameters,
           new List<DartType>.filled(
               calleeTypeParameters.length, const DynamicType()));
     }
     // TODO(paulberry): if we are doing top level inference and type arguments
     // were omitted, report an error.
-    if (!isTopLevel || isOverloadedArithmeticOperator) {
+    if (!isTopLevel ||
+        isOverloadedArithmeticOperator ||
+        TypeInferenceEngineImpl.expandedTopLevelInference) {
       int i = 0;
       _forEachArgument(arguments, (name, expression) {
         DartType formalType = name != null
             ? getNamedParameterType(calleeType, name)
             : getPositionalParameterType(calleeType, i++);
         DartType inferredFormalType = substitution != null
             ? substitution.substituteType(formalType)
             : formalType;
         var expressionType = inferExpression(
             expression,
@@ skipping 340 matching lines @@
   void _forEachArgument(
       Arguments arguments, void callback(String name, Expression expression)) {
     for (var expression in arguments.positional) {
       callback(null, expression);
     }
     for (var namedExpression in arguments.named) {
       callback(namedExpression.name, namedExpression.value);
     }
   }
 }