Fix a spurious warning in Frog selfhost

frog/value.dart

 // Copyright (c) 2011, 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.
 
 /**
  * Represents a meta-value for code generation.
  */
 class Value {
   /** The [Type] of the [Value]. */
   Type type;
@@ skipping 192 matching lines @@
     var callMethod = toType.getCallMethod();
     if (callMethod != null) {
       int arity = callMethod.parameters.length;
       var myCall = type.getCallMethod();
       if (myCall == null || myCall.parameters.length != arity) {
         return true;
       }
     }
     if (options.enableTypeChecks) {
       Type fromType = type;
-      if (type.isVar && code != 'null') {
+      if (type.isVar && (code != 'null' || !toType.isNullable)) {
         fromType = world.objectType;
       }
       bool bothNum = type.isNum && toType.isNum;
       return fromType.isSubtypeOf(toType) || bothNum;
     }
     return false;
   }
 
   /**
    * Assign or convert this value to another type.
@@ skipping 34 matching lines @@
     // and then only allowed Dynamic to be bottom for generic type args, I think
     // we'd get the right behavior from isSubtypeOf.
     Type fromType = type;
     if (type.isVar && (code != 'null' || !toType.isNullable)) {
       fromType = world.objectType;
     }
 
     // TODO(jmesserly): remove the special case for "num" when our num handling
     // is better.
     bool bothNum = type.isNum && toType.isNum;
-    if (!checked || fromType.isSubtypeOf(toType) || bothNum) {
+    if (fromType.isSubtypeOf(toType) || bothNum) {
       // No checks needed for a widening conversion.
       return this;
     }
 
     if (checked && !toType.isSubtypeOf(type)) {
       // According to the static types, this conversion can't work.
       convertWarning(toType, node);
     }
 
     // Generate a runtime checks if they're turned on, otherwise skip it.
@@ skipping 17 matching lines @@
    * Generates a run time type assertion for the given value. This works like
    * [instanceOf], but it allows null since Dart types are nullable.
    * Also it will throw a TypeError if it gets the wrong type.
    */
   Value _typeAssert(MethodGenerator context, Type toType, Node node) {
     if (toType is ParameterType) {
       ParameterType p = toType;
       toType = p.extendsType;
     }
 
+    // TODO(jmesserly): fix checking of function types.
+    // For now, don't generate a broken check.
+    if (toType.getCallMethod() != null) {
+      return this;
+    }
+
     if (toType.isObject || toType.isVar) {
       world.internalError('We thought ${type.name} is not a subtype of ${toType.name}?');
     }
 
     // TODO(jmesserly): better assert for integers?
     if (toType.isNum) toType = world.numType;
 
     // Generate a check like these:
     //   obj && obj.is$TypeName()
     //   $assert_int(obj)
@@ skipping 352 matching lines @@
 
     // Then look for members in my library.
     member = home.library.lookup(name, span);
     if (member != null) {
       return member;
     }
 
     return null;
   }
 }