Support type variables on redirecting factory constructors.

sdk/lib/_internal/compiler/implementation/ssa/builder.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.
 
 part of ssa;
 
 /**
  * A special element for the extra parameter taken by intercepted
  * methods. We need to override [Element.computeType] because our
  * optimizers may look at its declared type.
@@ skipping 3213 matching lines @@
       } else {
         return HType.UNKNOWN;
       }
     }
 
     Element constructor = elements[node];
     Selector selector = elements.getSelector(node);
     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);
     add(target);
     var inputs = <HInstruction>[];
     inputs.add(target);
     // TODO(5347): Try to avoid the need for calling [implementation] before
     // calling [addStaticSendArgumentsToList].
     bool succeeded = addStaticSendArgumentsToList(selector, node.arguments,
                                                   constructor.implementation,
@@ skipping 238 matching lines @@
       Constant constant = handler.compileNodeWithDefinitions(node, elements);
       stack.add(graph.addConstant(constant));
     } else {
       DartType type = elements.getType(node);
       if (compiler.enableTypeAssertions && type.isMalformed) {
         String reasons = Types.fetchReasonsFromMalformedType(type);
         // TODO(johnniwinther): Change to resemble type errors from bounds check
         // 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);
       }
     }
   }
 
   HInvokeDynamicMethod buildInvokeDynamic(Node node,
                                           Selector selector,
                                           HInstruction receiver,
                                           List<HInstruction> arguments) {
     Set<ClassElement> interceptedClasses = getInterceptedClassesOn(selector);
@@ skipping 1445 matching lines @@
           new HSubGraphBlockInformation(elseBranch.graph));
 
     HBasicBlock conditionStartBlock = conditionBranch.block;
     conditionStartBlock.setBlockFlow(info, joinBlock);
     SubGraph conditionGraph = conditionBranch.graph;
     HIf branch = conditionGraph.end.last;
     assert(branch is HIf);
     branch.blockInformation = conditionStartBlock.blockFlow;
   }
 }