Fix 'Extract Method' refactoring inside extensions.

Change-Id: If055456980361c5ec768bf5cb104af11cfa1b12e
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/323704
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Reviewed-by: Phil Quitslund <pquitslund@google.com>
Commit-Queue: Konstantin Shcheglov <scheglov@google.com>

Author: scheglov

pkg/analysis_server/lib/src/services/correction/util.dart

@@ -247,6 +247,7 @@ AstNode? getEnclosingClassOrUnitMember(AstNode input) {
       case ClassDeclaration _:
       case CompilationUnit _:
       case EnumDeclaration _:
+      case ExtensionDeclaration _:
       case ExtensionTypeDeclaration _:
       case MixinDeclaration _:
         return member;

pkg/analysis_server/test/services/refactoring/legacy/extract_method_test.dart

@@ -12,6 +12,7 @@ import 'abstract_refactoring.dart';
 void main() {
   defineReflectiveSuite(() {
     defineReflectiveTests(ExtractMethodTest_Enum);
+    defineReflectiveTests(ExtractMethodTest_Extension);
     defineReflectiveTests(ExtractMethodTest_ExtensionType);
     defineReflectiveTests(ExtractMethodTest_Mixin);
     defineReflectiveTests(ExtractMethodTest);
@@ -3338,6 +3339,57 @@ enum E {
   }
 }
 
+@reflectiveTest
+class ExtractMethodTest_Extension extends _ExtractMethodTest {
+  Future<void> test_singleExpression_method() async {
+    await indexTestUnit('''
+extension E on int {
+  void foo() {
+    int a = 1 + 2;
+  }
+}
+''');
+    _createRefactoringForString('1 + 2');
+    // apply refactoring
+    return _assertSuccessfulRefactoring('''
+extension E on int {
+  void foo() {
+    int a = res();
+  }
+
+  int res() => 1 + 2;
+}
+''');
+  }
+
+  Future<void> test_statements_method() async {
+    await indexTestUnit('''
+extension E on int {
+  void foo() {
+// start
+    print(0);
+// end
+  }
+}
+''');
+    _createRefactoringForStartEndComments();
+    // apply refactoring
+    return _assertSuccessfulRefactoring('''
+extension E on int {
+  void foo() {
+// start
+    res();
+// end
+  }
+
+  void res() {
+    print(0);
+  }
+}
+''');
+  }
+}
+
 @reflectiveTest
 class ExtractMethodTest_ExtensionType extends _ExtractMethodTest {
   Future<void> test_bad_conflict_method_alreadyDeclaresMethod() async {