Add tests, including test for issue

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/utilities.dart';
 import 'package:analyzer/src/generated/engine.dart';
@@ skipping 18 matching lines @@
 }
 
 SimpleIdentifier _findSimpleIdentifier(
     AstNode root, String code, String search) {
   return EngineTestCase.findNode(
       root, code, search, (n) => n is SimpleIdentifier);
 }
 
 @reflectiveTest
 class DeclarationResolverTest extends ResolverTestCase {
+  void fail_visitMethodDeclaration_setter_duplicate() {
+    // https://github.com/dart-lang/sdk/issues/25601
+    String code = r'''
+class C {
+  set zzz(x) {}
+  set zzz(y) {}
+}
+''';
+    CompilationUnit unit = resolveSource(code);
+    PropertyAccessorElement firstElement =
+        _findSimpleIdentifier(unit, code, 'zzz(x)').staticElement;
+    PropertyAccessorElement secondElement =
+        _findSimpleIdentifier(unit, code, 'zzz(y)').staticElement;
+    // re-resolve
+    CompilationUnit unit2 = _cloneResolveUnit(unit);
+    SimpleIdentifier firstName = _findSimpleIdentifier(unit2, code, 'zzz(x)');
+    SimpleIdentifier secondName = _findSimpleIdentifier(unit2, code, 'zzz(y)');
+    expect(firstName.staticElement, same(firstElement));
+    expect(secondName.staticElement, same(secondElement));
+  }
+
   @override
   void setUp() {
     super.setUp();
   }
 
   void test_functionDeclaration_getter() {
     String code = r'''
 int get zzz => 42;
 ''';
     CompilationUnit unit = resolveSource(code);
@@ skipping 42 matching lines @@
 }
 ''';
     CompilationUnit unit = resolveSource(code);
     FunctionElement setterElement =
         _findSimpleIdentifier(unit, code, 'zzz(x)').staticElement;
     // re-resolve
     CompilationUnit unit2 = _cloneResolveUnit(unit);
     SimpleIdentifier setterName = _findSimpleIdentifier(unit2, code, 'zzz(x)');
     expect(setterName.staticElement, same(setterElement));
   }
+
+  void test_visitMethodDeclaration_getter_duplicate() {
+    String code = r'''
+class C {
+  int get zzz => 1;
+  String get zzz => null;
+}
+''';
+    CompilationUnit unit = resolveSource(code);
+    PropertyAccessorElement firstElement =
+        _findSimpleIdentifier(unit, code, 'zzz => 1').staticElement;
+    PropertyAccessorElement secondElement =
+        _findSimpleIdentifier(unit, code, 'zzz => null').staticElement;
+    // re-resolve
+    CompilationUnit unit2 = _cloneResolveUnit(unit);
+    SimpleIdentifier firstName = _findSimpleIdentifier(unit2, code, 'zzz => 1');
+    SimpleIdentifier secondName =
+        _findSimpleIdentifier(unit2, code, 'zzz => null');
+    expect(firstName.staticElement, same(firstElement));
+    expect(secondName.staticElement, same(secondElement));
+  }
+
+  void test_visitMethodDeclaration_method_duplicate() {
+    String code = r'''
+class C {
+  void zzz(x) {}
+  void zzz(y) {}
+}
+''';
+    CompilationUnit unit = resolveSource(code);
+    MethodElement firstElement =
+        _findSimpleIdentifier(unit, code, 'zzz(x)').staticElement;
+    MethodElement secondElement =
+        _findSimpleIdentifier(unit, code, 'zzz(y)').staticElement;
+    // re-resolve
+    CompilationUnit unit2 = _cloneResolveUnit(unit);
+    SimpleIdentifier firstName = _findSimpleIdentifier(unit2, code, 'zzz(x)');
+    SimpleIdentifier secondName = _findSimpleIdentifier(unit2, code, 'zzz(y)');
+    expect(firstName.staticElement, same(firstElement));
+    expect(secondName.staticElement, same(secondElement));
+  }
 }
 
 /**
  * Strong mode DeclarationResolver tests
  */
 @reflectiveTest
 class StrongModeDeclarationResolverTest extends ResolverTestCase {
   @override
   void setUp() {
     resetWithOptions(new AnalysisOptionsImpl()..strongMode = true);
@@ skipping 38 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));
   }
 }