Remove hack from KernelTypePromoter.isPromotionCandidate.

pkg/front_end/lib/src/fasta/kernel/kernel_shadow_ast.dart

 // Copyright (c) 2017, 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.
 
 /// This file declares a "shadow hierarchy" of concrete classes which extend
 /// the kernel class hierarchy, adding methods and fields needed by the
 /// BodyBuilder.
 ///
 /// Instances of these classes may be created using the factory methods in
 /// `ast_factory.dart`.
@@ skipping 2116 matching lines @@
       // Hack to deal with the fact that BodyBuilder still creates raw
       // VariableDeclaration objects sometimes.
       // TODO(paulberry): get rid of this once the type parameter is
       // KernelVariableDeclaration.
       return 0;
     }
   }
 
   @override
   bool isPromotionCandidate(VariableDeclaration variable) {
-    if (variable is KernelVariableDeclaration) {
-      return !variable._isLocalFunction;
-    } else {
-      // Hack to deal with the fact that BodyBuilder still creates raw
-      // VariableDeclaration objects sometimes.
-      // TODO(paulberry): get rid of this once the type parameter is
-      // KernelVariableDeclaration.
-      return true;
-    }
+    assert(variable is KernelVariableDeclaration);
+    KernelVariableDeclaration kernelVariableDeclaration = variable;
+    return !kernelVariableDeclaration._isLocalFunction;
   }
 
   @override
   bool sameExpressions(Expression a, Expression b) {
     return identical(a, b);
   }
 
   @override
   void setVariableMutatedAnywhere(VariableDeclaration variable) {
     if (variable is KernelVariableDeclaration) {
@@ skipping 205 matching lines @@
   }
 
   transformChildren(v) {
     return internalError("Internal error: Unsupported operation.");
   }
 
   visitChildren(v) {
     return internalError("Internal error: Unsupported operation.");
   }
 }