Don't treat typedef-typed formal parameters as funtion-type from resynthesize from Kernel.

pkg/analyzer/lib/src/dart/element/element.dart

 // Copyright (c) 2014, 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.
 
 library analyzer.src.dart.element.element;
 
 import 'dart:collection';
 import 'dart:math' show min;
 
 import 'package:analyzer/dart/ast/ast.dart';
@@ skipping 8463 matching lines @@
   }
 
   /**
    * If this element is resynthesized, and its type and parameters have not
    * been build yet, build them and remember in the corresponding fields.
    */
   void _resynthesizeTypeAndParameters() {
     if (_kernel != null && _type == null) {
       kernel.DartType type = _kernel.type;
       _type = enclosingUnit._kernelContext.getType(this, type);
-      if (type is kernel.FunctionType) {
+      if (type is kernel.FunctionType && type.typedefReference == null) {
         _parameters = new List<ParameterElement>(
             type.positionalParameters.length + type.namedParameters.length);
         int index = 0;
         for (int i = 0; i < type.positionalParameters.length; i++) {
           String name = i < type.positionalParameterNames.length
               ? type.positionalParameterNames[i]
               : null;
           _parameters[index++] = new ParameterElementImpl.forKernel(
               enclosingElement,
               new kernel.VariableDeclaration(name,
@@ skipping 1520 matching lines @@
 
   @override
   DartObject computeConstantValue() => null;
 
   @override
   void visitChildren(ElementVisitor visitor) {
     super.visitChildren(visitor);
     _initializer?.accept(visitor);
   }
 }