Resolve redirecting factories.

dart/sdk/lib/_internal/compiler/implementation/resolution/members.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 resolution;
 
 abstract class TreeElements {
   Element operator[](Node node);
   Selector getSelector(Send send);
   DartType getType(Node node);
@@ skipping 1857 matching lines @@
       visit(link.head);
     }
   }
 
   visitOperator(Operator node) {
     unimplemented(node, 'operator');
   }
 
   visitReturn(Return node) {
     if (node.isRedirectingFactoryBody) {
-      unimplemented(node, 'redirecting constructors');
+      useElement(node.expression, resolveRedirectingFactory(node));
+    } else {
+      visit(node.expression);
     }
-    visit(node.expression);
   }
 
   visitThrow(Throw node) {
     if (!inCatchBlock && node.expression == null) {
       error(node, MessageKind.THROW_WITHOUT_EXPRESSION);
     }
     visit(node.expression);
   }
 
   visitVariableDefinitions(VariableDefinitions node) {
@@ skipping 53 matching lines @@
 
   /**
    * Try to resolve the constructor that is referred to by [node].
    * Note: this function may return an ErroneousFunctionElement instead of
    * [null], if there is no corresponding constructor, class or library.
    */
   FunctionElement resolveConstructor(NewExpression node) {
     return node.accept(new ConstructorResolver(compiler, this));
   }
 
+  FunctionElement resolveRedirectingFactory(Return node) {
+    return node.accept(new ConstructorResolver(compiler, this));
+  }
+
   DartType resolveTypeRequired(TypeAnnotation node) {
     bool old = typeRequired;
     typeRequired = true;
     DartType result = resolveTypeAnnotation(node);
     typeRequired = old;
     return result;
   }
 
   void analyzeTypeArgument(DartType annotation, DartType argument) {
     if (argument == null) return;
@@ skipping 974 matching lines @@
     } else if (inConstContext && !result.modifiers.isConst()) {
       error(diagnosticNode, MessageKind.CONSTRUCTOR_IS_NOT_CONST);
     }
     return result;
   }
 
   visitNewExpression(NewExpression node) {
     inConstContext = node.isConst();
     Node selector = node.send.selector;
     Element e = visit(selector);
-    if (!Elements.isUnresolved(e) && identical(e.kind, ElementKind.CLASS)) {
+    return finishConstructorReference(e, node.send.selector, node);
+  }
+
+  /// Finishes resolution of a constructor reference and records the
+  /// type of the constructed instance on [expression].
+  FunctionElement finishConstructorReference(Element e,
+                                             Node diagnosticNode,
+                                             Expression expression) {
+    // Find the unnamed constructor if the reference resolved to a
+    // class.
+    if (!Elements.isUnresolved(e) && e.isClass()) {
       ClassElement cls = e;
       cls.ensureResolved(compiler);
       if (cls.isInterface() && (cls.defaultClass == null)) {
-        error(selector, MessageKind.CANNOT_INSTANTIATE_INTERFACE, [cls.name]);
+        // TODO(ahe): Remove this check and error message when we
+        // don't have interfaces anymore.
+        error(diagnosticNode,
+              MessageKind.CANNOT_INSTANTIATE_INTERFACE, [cls.name]);
       }
-      e = lookupConstructor(cls, selector, const SourceString(''));
+      // The unnamed constructor may not exist, so [e] may become unresolved.
+      e = lookupConstructor(cls, diagnosticNode, const SourceString(''));
     }
     if (type == null) {
       if (Elements.isUnresolved(e)) {
         type = compiler.dynamicClass.computeType(compiler);
       } else {
         type = e.getEnclosingClass().computeType(compiler).asRaw();
       }
     }
-    resolver.mapping.setType(node, type);
+    resolver.mapping.setType(expression, type);
     return e;
   }
 
   visitTypeAnnotation(TypeAnnotation node) {
     assert(invariant(node, type == null));
     type = resolver.resolveTypeRequired(node);
     return resolver.mapping[node];
   }
 
   visitSend(Send node) {
@@ skipping 37 matching lines @@
     } else if (identical(e.kind, ElementKind.TYPEDEF)) {
       error(node, MessageKind.CANNOT_INSTANTIATE_TYPEDEF, [name]);
     } else if (identical(e.kind, ElementKind.TYPE_VARIABLE)) {
       error(node, MessageKind.CANNOT_INSTANTIATE_TYPE_VARIABLE, [name]);
     } else if (!identical(e.kind, ElementKind.CLASS)
         && !identical(e.kind, ElementKind.PREFIX)) {
       error(node, MessageKind.NOT_A_TYPE, [name]);
     }
     return e;
   }
+
+  /// Assumed to be called by [resolveRedirectingFactory].
+  Element visitReturn(Return node) {
+    Expression expression = node.expression;
+    return finishConstructorReference(visit(expression),
+                                      expression, expression);
+  }
 }