Implement is-checks against type variables.

sdk/lib/_internal/compiler/implementation/ssa/builder.dart

Index: sdk/lib/_internal/compiler/implementation/ssa/builder.dart
diff --git a/sdk/lib/_internal/compiler/implementation/ssa/builder.dart b/sdk/lib/_internal/compiler/implementation/ssa/builder.dart
index 916b4db455b607d3cadbc8515509c6cd046c6906..49e12e816ec63a460f4314ec4d08f83b0d21e5ba 100644
--- a/sdk/lib/_internal/compiler/implementation/ssa/builder.dart
+++ b/sdk/lib/_internal/compiler/implementation/ssa/builder.dart
@@ -2642,16 +2642,23 @@ class SsaBuilder extends ResolvedVisitor implements Visitor {
         }
         return;
       }
-      if (type.element.isTypeVariable()) {
-        // TODO(karlklose): remove this check when the backend can deal with
-        // checks of the form [:o is T:] where [:T:] is a type variable.
-        stack.add(graph.addConstantBool(true, constantSystem));
-        return;
-      }
 
       HInstruction instruction;
-      if (type.element.isTypeVariable() ||
-          RuntimeTypeInformation.hasTypeArguments(type)) {
+      if (type.element.isTypeVariable()) {

[ngeoffray, 2013/02/18 09:27:58]

Don't we have a check on the type to know if it's a type variable?

[karlklose, 2013/02/18 16:02:01]

No, we only have these helpers on elements. Replaced it with a test of the
TypeKind.

+        List<HInstruction> representations =
+            buildTypeArgumentRepresentations(type);
+        assert(representations.length == 1);
+        HInstruction runtimeType = representations[0];

[ngeoffray, 2013/02/18 09:27:58]

Instead of asserting it's 1 and fetching the first element, have to methods for
buildTypeArgumentRepresentations: one for type variable, and one for the other
cases?

[karlklose, 2013/02/18 16:02:01]

Done.

+        Element helper =
+            compiler.findHelper(const SourceString('objectIsSubtype'));
+        HInstruction helperCall = new HStatic(helper);
+        add(helperCall);
+        List<HInstruction> inputs = <HInstruction>[helperCall, expression,
+                                                   runtimeType];
+        instruction = new HInvokeStatic(inputs, HType.UNKNOWN);

[ngeoffray, 2013/02/18 09:27:58]

HType.BOOLEAN?

[karlklose, 2013/02/18 16:02:01]

Done.

+        add(instruction);

[ngeoffray, 2013/02/18 09:27:58]

Register in codegen world?

[karlklose, 2013/02/18 16:02:01]

Done.

+
+      } else if (RuntimeTypeInformation.hasTypeArguments(type)) {
 
         void argumentsCheck() {
           HInstruction typeInfo = getRuntimeTypeInfo(expression);
@@ -2681,7 +2688,8 @@ class SsaBuilder extends ResolvedVisitor implements Visitor {
         void classCheck() { push(new HIs(type, <HInstruction>[expression])); }
 
         SsaBranchBuilder branchBuilder = new SsaBranchBuilder(this, node);
-        branchBuilder.handleLogicalAndOr(classCheck, argumentsCheck, isAnd: true);
+        branchBuilder.handleLogicalAndOr(classCheck, argumentsCheck,
+                                         isAnd: true);
         instruction = pop();
       } else {
         instruction = new HIs(type, <HInstruction>[expression]);