Ensure interfaces are loaded.

dart/lib/compiler/implementation/typechecker.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.
 
 class TypeCheckerTask extends CompilerTask {
   TypeCheckerTask(Compiler compiler) : super(compiler);
   String get name() => "Type checker";
 
   static final bool LOG_FAILURES = false;
 
@@ skipping 75 matching lines @@
       sb.add('<');
       arguments.printOn(sb, ', ');
       sb.add('>');
     }
     return sb.toString();
   }
 }
 
 class FunctionType implements Type {
   final Element element;
-  final Type returnType;
-  final Link<Type> parameterTypes;
+  Type returnType;
+  Link<Type> parameterTypes;
 
-  const FunctionType(Type this.returnType, Link<Type> this.parameterTypes,
-                     Element this.element);
+  FunctionType(Type this.returnType, Link<Type> this.parameterTypes,
+               Element this.element);
 
   toString() {
     StringBuffer sb = new StringBuffer();
     bool first = true;
     sb.add('(');
     parameterTypes.printOn(sb, ', ');
     sb.add(') -> ${returnType}');
     return sb.toString();
   }
 
   SourceString get name() => const SourceString('Function');
 
   int computeArity() {
     int arity = 0;
     parameterTypes.forEach((_) { arity++; });
     return arity;
   }
+
+  void initializeFrom(FunctionType other) {

[Lasse Reichstein Nielsen, 2012/08/07 09:02:17]

Why is this not a constructor?
I only see one use of it, and that's on a newly created FunctionType object.
I.e., I suggest:

FunctionType.from(FunctionType other, Element this.element) : returnType =
other.returnType, parameterTypes = other.parameterTypes;

+    assert(returnType === null);
+    assert(parameterTypes === null);
+    returnType = other.returnType;
+    parameterTypes = other.parameterTypes;
+  }
 }
 
 class Types {
   final VoidType voidType;
   final InterfaceType dynamicType;
 
   Types(Element dynamicElement)
     : this.with(dynamicElement, new LibraryElement(new Script(null, null)));
 
   // TODO(karlklose): should we have a class Void?
@@ skipping 646 matching lines @@
   }
 
   visitCatchBlock(CatchBlock node) {
     return unhandledStatement();
   }
 
   visitTypedef(Typedef node) {
     return unhandledStatement();
   }
 }