dart2js inferrer: don't infer widened type when unreachable

pkg/compiler/lib/src/inferrer/inferrer_visitor.dart

 // Copyright (c) 2013, 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 inferrer_visitor;
 
 import 'dart:collection' show IterableMixin;
 
 import '../common.dart';
 import '../compiler.dart' show Compiler;
@@ skipping 296 matching lines @@
     named.forEach((name, type) {
       if (other.named[name] != type) return false;
     });
     return true;
   }
 
   int get hashCode => throw new UnsupportedError('ArgumentsTypes.hashCode');
 
   bool hasNoArguments() => positional.isEmpty && named.isEmpty;
 
-  bool hasOnePositionalArgumentThatMatches(bool f(T type)) {
-    return named.isEmpty && positional.length == 1 && f(positional[0]);
-  }
-
   void forEach(void f(T type)) {
     positional.forEach(f);
     named.values.forEach(f);
   }
 
   bool every(bool f(T type)) {
     return positional.every(f) && named.values.every(f);
   }
 
   bool contains(T type) {
@@ skipping 1156 matching lines @@
     return type;
   }
 
   T visitCascade(Cascade node) {
     // Ignore the result of the cascade send and return the type of the cascade
     // receiver.
     visit(node.expression);
     return cascadeReceiverStack.removeLast();
   }
 }