Clean up some warnings (issue 25964)

pkg/analyzer/test/generated/declaration_resolver_test.dart

 // Copyright (c) 2015, 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 engine.declaration_resolver_test;
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/src/dart/ast/ast.dart';
 import 'package:analyzer/src/dart/ast/utilities.dart';
@@ skipping 249 matching lines @@
 
   void test_enumConstant_partiallyResolved() {
     String code = r'''
 enum Fruit {apple, pear}
 ''';
     Source source = addNamedSource('/test.dart', code);
     LibrarySpecificUnit target = new LibrarySpecificUnit(source, source);
     analysisContext.computeResult(source, LIBRARY_ELEMENT1);
     CompilationUnit unit =
         analysisContext.computeResult(target, RESOLVED_UNIT1);
-    CompilationUnit unit2 = _cloneResolveUnit(unit);
+    _cloneResolveUnit(unit);
   }
 
   void test_functionDeclaration_getter() {
     String code = r'''
 int get zzz => 42;
 ''';
     CompilationUnit unit = resolveSource(code);
     PropertyAccessorElement getterElement =
         _findSimpleIdentifier(unit, code, 'zzz =>').staticElement;
     expect(getterElement.isGetter, isTrue);
@@ skipping 255 matching lines @@
     expect(element.type.toString(), "<T>(T, T) → T");
     expect(t.element, same(tElement));
 
     // re-resolve
     CompilationUnit unit2 = _cloneResolveUnit(unit);
     node = _findSimpleIdentifier(unit2, code, 'max').parent;
     t = node.typeParameters.typeParameters[0];
     expect(t.element, same(tElement));
   }
 }