Support for "a is Function".

frog/leg/ssa/closure.dart

 // Copyright (c) 2012, 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.
 
 class ClosureFieldElement extends Element {
   ClosureFieldElement(SourceString name, ClassElement enclosing)
       : super(name, ElementKind.FIELD, enclosing);
 
   bool isInstanceMember() => true;
   bool isAssignable() => false;
 
   String toString() => "ClosureFieldElement($name)";
 }
 
+class ClosureClassElement extends ClassElement {
+  ClosureClassElement(Compiler compiler, Element enclosingElement)
+      : super(Compiler.CLOSURE, enclosingElement) {
+    isResolved = true;
+    compiler.closureClass.ensureResolved(compiler);
+    supertype = compiler.closureClass.computeType(compiler);
+  }
+}
+
 // The box-element for a scope, and the captured variables that need to be
 // stored in the box.
 class ClosureScope {
   Element boxElement;
   Map<Element, Element> capturedVariableMapping;
   // If the scope is attached to a [For] contains the variables that are
   // declared in the initializer of the [For] and that need to be boxed.
   // Otherwise contains the empty List.
   List<Element> boxedLoopVariables;
 
@@ skipping 260 matching lines @@
       Element element = elements[definition];
       if (capturedVariableMapping.containsKey(element)) {
         result.add(element);
       };
     }
     scopeData.boxedLoopVariables = result;
   }
 
   ClosureData globalizeClosure(FunctionExpression node) {
     FunctionElement element = elements[node];
-    SourceString name = const SourceString("Closure");
-    CompilationUnitElement compilationUnit = element.getCompilationUnit();
-    ClassElement globalizedElement = new ClassElement(name, compilationUnit);
+    ClassElement globalizedElement =
+        new ClosureClassElement(compiler, element.getCompilationUnit());
     FunctionElement callElement =
         new FunctionElement.from(Namer.CLOSURE_INVOCATION_NAME,
                                  element,
                                  globalizedElement);
     globalizedElement.backendMembers =
         const EmptyLink<Element>().prepend(callElement);
-    globalizedElement.isResolved = true;
-    // TODO(karlklose): create function to get the resolved class object.
-    ClassElement objectClass = compiler.coreLibrary.find(Types.OBJECT);
-    globalizedElement.supertype = objectClass.computeType(compiler);
-    objectClass.ensureResolved(compiler);
     // The nested function's 'this' is the same as the one for the outer
     // function. It could be [null] if we are inside a static method.
     Element thisElement = closureData.thisElement;
     return new ClosureData(element, globalizedElement,
                            callElement, thisElement);
   }
 
   visitFunctionExpression(FunctionExpression node) {
     Element element = elements[node];
     if (element.kind === ElementKind.PARAMETER) {
@@ skipping 86 matching lines @@
     declareLocal(elements[node]);
   }
 
   visitTryStatement(TryStatement node) {
     // TODO(ngeoffray): implement finer grain state.
     inTryCatchOrFinally = true;
     node.visitChildren(this);
     inTryCatchOrFinally = false;
   }
 }