Allow arity checks on dynamic function types

lib/src/checker/checker.dart

 // Copyright (c) 2015, 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.
 
 library dev_compiler.src.checker.checker;
 
 import 'package:analyzer/analyzer.dart';
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/element.dart';
 import 'package:analyzer/src/generated/scanner.dart' show Token, TokenType;
@@ skipping 657 matching lines @@
   }
 
   void _checkRuntimeTypeCheck(AstNode node, TypeName typeName) {
     var type = getType(typeName);
     if (!_rules.isGroundType(type)) {
       _recordMessage(new InvalidRuntimeCheckError(node, type));
     }
   }
 
   visitAsExpression(AsExpression node) {
+    // We could do the same check as the IsExpression below, but that is
+    // potentially too conservative.  Instead, at runtime, we must fail hard
+    // if the Dart as and the DDC as would return different values.
     node.visitChildren(this);
   }
 
   visitIsExpression(IsExpression node) {
     _checkRuntimeTypeCheck(node, node.type);
     node.visitChildren(this);
   }
 
   DartType getType(TypeName name) {
     return (name == null) ? _rules.provider.dynamicType : name.type;
@@ skipping 85 matching lines @@
   void _recordDynamicInvoke(AstNode node) {
     _reporter.log(new DynamicInvoke(_rules, node));
   }
 
   void _recordMessage(StaticInfo info) {
     if (info == null) return;
     if (info.level >= logger.Level.SEVERE) _failure = true;
     _reporter.log(info);
   }
 }