Fix top level type inference for binary operators.

pkg/front_end/lib/src/fasta/kernel/kernel_shadow_ast.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 file.
 
 /// This file declares a "shadow hierarchy" of concrete classes which extend
 /// the kernel class hierarchy, adding methods and fields needed by the
 /// BodyBuilder.
 ///
 /// Instances of these classes may be created using the factory methods in
 /// `ast_factory.dart`.
@@ skipping 1255 matching lines @@
   KernelMethodInvocation(Expression receiver, Name name, Arguments arguments,
       {bool isImplicitCall: false, Member interfaceTarget})
       : _isImplicitCall = isImplicitCall,
         super(receiver, name, arguments, interfaceTarget);
 
   @override
   void _collectDependencies(KernelDependencyCollector collector) {
     // The inference dependencies are the inference dependencies of the
     // receiver.
     collector.collectDependencies(receiver);
+    if (name == '+' || name == '-' || name == '*' || name == '%') {

[scheglov, 2017/06/13 19:46:51]

Is it unsafe to use identical() here?

[Paul Berry, 2017/06/13 20:06:39]

Oops, I should have thought of that.  identical() is better.  Fixed.

+      collector.collectDependencies(arguments.positional[0]);
+    }
   }
 
   @override
   DartType _inferExpression(
       KernelTypeInferrer inferrer, DartType typeContext, bool typeNeeded) {
     typeNeeded = inferrer.listener.methodInvocationEnter(this, typeContext) ||
         typeNeeded;
     // First infer the receiver so we can look up the method that was invoked.
     var receiverType = inferrer.inferExpression(receiver, null, true);
     bool isOverloadedArithmeticOperator = false;
@@ skipping 935 matching lines @@
   }
 
   transformChildren(v) {
     return internalError("Internal error: Unsupported operation.");
   }
 
   visitChildren(v) {
     return internalError("Internal error: Unsupported operation.");
   }
 }