Support type variables as expressions.

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 3055 matching lines @@
     SourceString name = selector.name;
 
     ClassElement cls = currentElement.getEnclosingClass();
     Element element = cls.lookupSuperMember(Compiler.NO_SUCH_METHOD);
     if (element.enclosingElement.declaration != compiler.objectClass) {
       // Register the call as dynamic if [:noSuchMethod:] on the super class
       // is _not_ the default implementation from [:Object:], in case
       // the [:noSuchMethod:] implementation does an [:invokeOn:] on
       // the invocation mirror.
       compiler.enqueuer.codegen.registerSelectorUse(selector);
-    }   
+    }
     HStatic target = new HStatic(element);
     add(target);
     HInstruction self = localsHandler.readThis();
     Constant nameConstant = constantSystem.createString(
         new DartString.literal(name.slowToString()), node);
 
     String internalName = backend.namer.invocationName(selector);
     Constant internalNameConstant =
         constantSystem.createString(new DartString.literal(internalName), node);
 
@@ skipping 66 matching lines @@
       HInstruction target = new HInvokeSuper(inputs);
       add(target);
       inputs = <HInstruction>[target];
       addDynamicSendArgumentsToList(node, inputs);
       Selector closureSelector = new Selector.callClosureFrom(selector);
       push(new HInvokeClosure(closureSelector, inputs));
     }
   }
 
   /**
+   * Generate code to extract the type arguments from the object, substitute
+   * them as an instance of the type we are testing against (if necessary), and
+   * extract the type argument by the index of the variable in the list of type
+   * variables for that class.
+   */
+  HInstruction readTypeVariable(ClassElement cls,
+                                TypeVariableElement variable) {
+    int index = RuntimeTypeInformation.getTypeVariableIndex(variable);
+    String substitutionNameString = backend.namer.substitutionName(cls);
+    HInstruction substitutionName = graph.addConstantString(
+        new LiteralDartString(substitutionNameString), null, constantSystem);
+    HInstruction target = localsHandler.readThis();
+    HInstruction substitution = createForeign('#[#]', HType.UNKNOWN,
+        <HInstruction>[target, substitutionName]);
+    add(substitution);
+    pushInvokeHelper3(backend.getGetRuntimeTypeArgument(),
+                      target,
+                      substitution,
+                      graph.addConstantInt(index, constantSystem),
+                      HType.UNKNOWN);
+    return pop();
+  }
+
+  /**
    * Helper to create an instruction that gets the value of a type variable.
    */
   HInstruction addTypeVariableReference(TypeVariableType type) {
     Element member = currentElement;
     if (member.enclosingElement.isClosure()) {
       ClosureClassElement closureClass = member.enclosingElement;
       member = closureClass.methodElement;
       member = member.getOutermostEnclosingMemberOrTopLevel();
     }
     if (member.isConstructor()
         || member.isGenerativeConstructorBody()
         || member.isField()) {
       // The type variable is stored in a parameter of the method.
       return localsHandler.readLocal(type.element);
     } else if (member.isInstanceMember()) {
-      // The type variable is stored on the object.  Generate code to extract
-      // the type arguments from the object, substitute them as an instance
-      // of the type we are testing against (if necessary), and extract the
-      // type argument by the index of the variable in the list of type
-      // variables for that class.
-      int index = RuntimeTypeInformation.getTypeVariableIndex(type);
-      HInstruction thisObject = localsHandler.readThis();
-      String substitutionNameString =
-          backend.namer.substitutionName(member.getEnclosingClass());
-      HInstruction substitutionName = graph.addConstantString(
-          new LiteralDartString(substitutionNameString), null, constantSystem);
-      HInstruction substitution = createForeign('#[#]', HType.UNKNOWN,
-          <HInstruction>[thisObject, substitutionName]);
-      add(substitution);
-      pushInvokeHelper3(backend.getGetRuntimeTypeArgument(),
-                        thisObject,
-                        substitution,
-                        graph.addConstantInt(index, constantSystem),
-                        HType.UNKNOWN);
-      return pop();
+      // The type variable is stored on the object.
+      return readTypeVariable(member.getEnclosingClass(),
+                              type.element);
     } else {
       // TODO(ngeoffray): Match the VM behavior and throw an
       // exception at runtime.
       compiler.cancel('Unimplemented unresolved type variable',
                       element: type.element);
     }
   }
 
   /**
    * Documentation wanted -- johnniwinther
@@ skipping 207 matching lines @@
   }
 
   visitTypeReferenceSend(Send node) {
     Element element = elements[node];
     if (element.isClass() || element.isTypedef()) {
       // TODO(karlklose): add type representation
       ConstantHandler handler = compiler.constantHandler;
       Constant constant = handler.compileNodeWithDefinitions(node, elements);
       stack.add(graph.addConstant(constant));
     } else if (element.isTypeVariable()) {
-      // TODO(6248): implement support for type variables.
-      compiler.unimplemented('first class type for type variable', node: node);
+      HInstruction value = readTypeVariable(currentElement.getEnclosingClass(),
+                                            element);
+      pushInvokeHelper1(backend.getRuntimeTypeToString(),
+                        value, HType.STRING);
+      pushInvokeHelper1(backend.getCreateRuntimeType(),
+                        pop(), HType.UNKNOWN);
     } else {
       internalError('unexpected element kind $element', node: node);
     }
     if (node.isCall) {
       // This send is of the form 'e(...)', where e is resolved to a type
       // reference. We create a regular closure call on the result of the type
       // reference instead of creating a NoSuchMethodError to avoid pulling it
       // in if it is not used (e.g., in a try/catch).
       HInstruction target = pop();
       Selector selector = elements.getSelector(node);
@@ skipping 1661 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;
   }
 }