Support type variables on redirecting factory constructors.

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 064a52e1e9d17b601b616bc2e70046c6282e69eb..feabe83347e25ce53eac07497ba532d5e05df2e0 100644
--- a/sdk/lib/_internal/compiler/implementation/ssa/builder.dart
+++ b/sdk/lib/_internal/compiler/implementation/ssa/builder.dart
@@ -3231,8 +3231,33 @@ class SsaBuilder extends ResolvedVisitor implements Visitor {
     if (compiler.enqueuer.resolution.getCachedElements(constructor) == null) {
       compiler.internalError("Unresolved element: $constructor", node: node);
     }
+
+    // Compute the right target and type for redirecting generative and
+    // factory constructors.

[ahe, 2013/01/29 09:30:58]

This should be done by the resolver. At least add a TODO.

[ngeoffray, 2013/01/29 09:37:22]

What would it take to move it to the resolver? Karl, any reason why you're doing
this here?

[karlklose, 2013/01/29 12:37:00]

Why do you think this belongs in the resolver (and what parts)?

This code is only computing the type arguments for the short-cut call to the
redirection target using already resolved types/elements.

     FunctionElement functionElement = constructor;
-    constructor = functionElement.redirectionTarget;

[ngeoffray, 2013/01/29 10:23:35]

@Peter: Why are we changing constructor here? The builder can do the general
inlining for you, we don't need to explicitly do it.

[ahe, 2013/01/29 10:57:48]

Because I didn't know better.

[ngeoffray, 2013/01/29 11:03:20]

After talking to Karl, it looks like we would still need to special case
something: the AST for the forwarding factory is pretty special:
Return(TypeAnnotation)

Compared to a regular factory:
Return(New(TypeAnnotation))

+    if (functionElement.redirectionTarget != functionElement) {
+      FunctionExpression functionNode = constructor.parseNode(compiler);
+      Node body = functionNode.body;
+      if (body != null && body.asReturn() != null &&
+          body.asReturn().isRedirectingFactoryBody) {
+        // Lookup the type expression used in the body and substitute the type
+        // variables with the call's type arguments in it.
+        Return redirectionNode = body;
+        TreeElements treeElements =
+            compiler.enqueuer.resolution.getCachedElements(
+                constructor.declaration);
+        ClassElement targetClass = constructor.getEnclosingClass();
+        DartType targetType = treeElements.getType(redirectionNode.expression);
+        Link<DartType> typeVariables = targetClass.typeVariables;
+        Link<DartType> typeArguments = type.typeArguments;
+        type = targetType.subst(typeArguments, typeVariables);
+      }
+      constructor = functionElement.redirectionTarget;
+    }
+
+    // TODO(karlklose): move this type registration to the codegen.
+    compiler.codegenWorld.instantiatedTypes.add(type);
+
     // TODO(5346): Try to avoid the need for calling [declaration] before
     // creating an [HStatic].
     HInstruction target = new HStatic(constructor.declaration);
@@ -3491,8 +3516,6 @@ class SsaBuilder extends ResolvedVisitor implements Visitor {
         // on type arguments.
         generateRuntimeError(node, '$type is malformed: $reasons');
       } else {
-        // TODO(karlklose): move this type registration to the codegen.
-        compiler.codegenWorld.instantiatedTypes.add(type);
         visitNewSend(node.send, type);
       }
     }