Type check untyped == calls specially.

lib/type_checker.dart

Index: lib/type_checker.dart
diff --git a/lib/type_checker.dart b/lib/type_checker.dart
index 4ebc31a15403c772a9eecd313a7cba81d915c031..ab47f6e328aead936a0dcab8cba10bcd766081cd 100644
--- a/lib/type_checker.dart
+++ b/lib/type_checker.dart
@@ -461,9 +461,14 @@ class TypeCheckingVisitor
     var target = node.interfaceTarget;
     if (target == null) {
       var receiver = visitExpression(node.receiver);
-      return (node.name.name == 'call' && receiver is FunctionType)
-          ? handleFunctionCall(node, receiver, node.arguments)
-          : handleDynamicCall(receiver, node.arguments);
+      if (node.name.name == '==') {
+        visitExpression(node.arguments.positional.single);
+        return environment.boolType;

[ahe, 2016/11/01 16:52:24]

I don't see how you know that you can return bool here. How do you know that the
argument is null or the receiver is null?

[asgerf, 2016/11/01 17:07:33]

In strong mode (which is what we are checking), operator== must return bool
because it overrides Object.==

+      }
+      if (node.name.name == 'call' && receiver is FunctionType) {
+        return handleFunctionCall(node, receiver, node.arguments);
+      }
+      return handleDynamicCall(receiver, node.arguments);
     } else if (environment.isOverloadedArithmeticOperator(target)) {
       assert(node.arguments.positional.length == 1);
       var receiver = visitExpression(node.receiver);