Adjusts dart2js backend to handle method type arguments.

pkg/compiler/lib/src/ssa/builder.dart

Index: pkg/compiler/lib/src/ssa/builder.dart
diff --git a/pkg/compiler/lib/src/ssa/builder.dart b/pkg/compiler/lib/src/ssa/builder.dart
index 1a754fd18f29628daabe4c52d8651e26dd3bbd0d..330c86fedef58473f7ccfc9133561f7c1bb18b9e 100644
--- a/pkg/compiler/lib/src/ssa/builder.dart
+++ b/pkg/compiler/lib/src/ssa/builder.dart
@@ -2594,6 +2594,10 @@ class SsaBuilder extends ast.Visitor
   HInstruction buildTypeConversion(
       HInstruction original, DartType type, int kind) {
     if (type == null) return original;
+    // TODO(eernst): The following statement was added for parsing and ignoring
+    // method type variables; must be generalized for full support of generic
+    // methods.
+    type = type.eraseMethodTypeVariableType;
     type = type.unaliased;
     assert(assertTypeInContext(type, original));
     if (type.isInterfaceType && !type.treatAsRaw) {
@@ -4772,6 +4776,17 @@ class SsaBuilder extends ast.Visitor
       // The type variable is stored on the object.
       return readTypeVariable(member.enclosingClass, type.element,
           sourceInformation: sourceInformation);
+    } else if (type is MethodTypeVariableType) {

[Johnni Winther, 2016/05/17 10:27:05]

When is this used?

[eernst, 2016/05/17 14:48:54]

I believe that it is not used any more: with the new approach, every
`MethodTypeVariableType` has been replaced by a `DynamicType` when this point is
reached. Rerunning tests confirm that there are no known situations where it is
needed. Removed the whole `else if (..) {..}` such that the pre-previous-CL form
of `addTypeVariableReference` is restored.

+      // TODO(eernst): The enclosing `else if` was added to provide minimal
+      // support for generic methods: The method type arguments are always
+      // pretending to have the value `dynamic`. Revise for full support.
+      DynamicType type = const DynamicType();
+      JavaScriptBackend backend = compiler.backend;
+      ClassElement cls = backend.helpers.DynamicRuntimeType;
+      HInstruction instruction =
+          new HDynamicType(type, new TypeMask.exact(cls, compiler.world));
+      add(instruction);
+      return instruction;
     } else {
       reporter.internalError(
           type.element, 'Unexpected type variable in static context.');