A bit of element model cleanup.

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 synthetic local variable only used with the SSA graph.
 ///
 /// For instance used for holding return value of function or the exception of a
 /// try-catch statement.
@@ skipping 38 matching lines @@
           } else {
             graph = builder.buildLazyInitializer(element);
           }
         } else {
           compiler.internalError(element, 'Unexpected element kind $kind.');
         }
         assert(graph.isValid());
         if (!identical(kind, ElementKind.FIELD)) {
           FunctionElement function = element;
           FunctionSignature signature = function.functionSignature;
-          signature.forEachOptionalParameter((Element parameter) {
+          signature.forEachOptionalParameter((ParameterElement parameter) {
             // This ensures the default value will be computed.
             Constant constant =
                 backend.constants.getConstantForVariable(parameter);
             CodegenRegistry registry = work.registry;
             registry.registerCompileTimeConstant(constant);
           });
         }
         if (compiler.tracer.isEnabled) {
           String name;
           if (element.isClassMember) {
@@ skipping 6334 matching lines @@
     if (unaliased is TypedefType) throw 'unable to unalias $type';
     unaliased.accept(this, builder);
   }
 
   void visitDynamicType(DynamicType type, SsaBuilder builder) {
     JavaScriptBackend backend = builder.compiler.backend;
     ClassElement cls = backend.findHelper('DynamicRuntimeType');
     builder.push(new HDynamicType(type, new TypeMask.exact(cls)));
   }
 }