Implement parsing and resolving of type-variables.

frog/leg/ssa/codegen.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 SsaCodeGeneratorTask extends CompilerTask {
   SsaCodeGeneratorTask(Compiler compiler) : super(compiler);
   String get name() => 'SSA code generator';
 
   String generate(WorkItem work, HGraph graph) {
     return measure(() {
@@ skipping 953 matching lines @@
 
   void checkType(HInstruction input, Element element) {
     buffer.add('!!');
     use(input, JSPrecedence.MEMBER_PRECEDENCE);
     buffer.add('.');
     buffer.add(compiler.namer.operatorIs(element));
   }
 
   void visitIs(HIs node) {
     Element element = node.typeExpression;
+    if (node.typeExpression.kind === ElementKind.TYPE_VARIABLE) {
+      compiler.unimplemented("visitIs for type variables");

[ngeoffray, 2012/03/18 13:40:57]

Do we actually end up here if the builder says unimplemented? Maybe add a
comment.

+    }
     compiler.registerIsCheck(element);
     LibraryElement coreLibrary = compiler.coreLibrary;
     ClassElement objectClass = coreLibrary.find(const SourceString('Object'));
     HInstruction input = node.expression;
     if (node.nullOk) {
       beginExpression(JSPrecedence.LOGICAL_OR_PRECEDENCE);
       checkNull(input);
       buffer.add(' || ');
     }
     if (element == objectClass) {
@@ skipping 447 matching lines @@
       startBailoutSwitch();
     }
   }
 
   void endElse(HIf node) {
     if (node.elseBlock.hasBailouts()) {
       endBailoutSwitch();
     }
   }
 }