Extensions are always enabled, merge corresponding tests.

Change-Id: I2a2603ea506baaf95ce26da656cee965faf094c2
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/149608
Reviewed-by: Brian Wilkerson <[email protected]>
Commit-Queue: Konstantin Shcheglov <[email protected]>

Author: scheglov

pkg/analyzer/test/generated/parser_fasta_test.dart

@@ -1648,21 +1648,6 @@ class ExpressionParserTest_Fasta extends FastaParserTestCase
 
 @reflectiveTest
 class ExtensionMethodsParserTest_Fasta extends FastaParserTestCase {
-  @override
-  CompilationUnit parseCompilationUnit(String content,
-      {List<ErrorCode> codes,
-      List<ExpectedError> errors,
-      FeatureSet featureSet}) {
-    return super.parseCompilationUnit(content,
-        codes: codes,
-        errors: errors,
-        featureSet: featureSet ??
-            FeatureSet.forTesting(
-              sdkVersion: '2.3.0',
-              additionalFeatures: [Feature.extension_methods],
-            ));
-  }
-
   void test_complex_extends() {
     var unit = parseCompilationUnit(
         'extension E extends A with B, C implements D { }',
@@ -2723,28 +2708,6 @@ main() {
     parseCompilationUnit('D? foo(X? x) { X? x1; X? x2 = x; }');
   }
 
-  void test_bangQuestionIndex() {
-    // http://dartbug.com/41177
-    CompilationUnit unit = parseCompilationUnit('f(dynamic a) { a!?[0]; }');
-    FunctionDeclaration funct = unit.declarations[0];
-    BlockFunctionBody body = funct.functionExpression.body;
-
-    ExpressionStatement statement = body.block.statements[0];
-    IndexExpression expression = statement.expression;
-
-    IntegerLiteral index = expression.index;
-    expect(index.value, 0);
-
-    Token question = expression.question;
-    expect(question, isNotNull);
-    expect(question.lexeme, "?");
-
-    PostfixExpression target = expression.target;
-    SimpleIdentifier identifier = target.operand;
-    expect(identifier.name, 'a');
-    expect(target.operator.lexeme, '!');
-  }
-
   void test_bangBeforeFuctionCall1() {
     // https://github.com/dart-lang/sdk/issues/39776
     var unit = parseCompilationUnit('f() { Function? f1; f1!(42); }');
@@ -2797,6 +2760,28 @@ main() {
     expect(argument.value, 42);
   }
 
+  void test_bangQuestionIndex() {
+    // http://dartbug.com/41177
+    CompilationUnit unit = parseCompilationUnit('f(dynamic a) { a!?[0]; }');
+    FunctionDeclaration funct = unit.declarations[0];
+    BlockFunctionBody body = funct.functionExpression.body;
+
+    ExpressionStatement statement = body.block.statements[0];
+    IndexExpression expression = statement.expression;
+
+    IntegerLiteral index = expression.index;
+    expect(index.value, 0);
+
+    Token question = expression.question;
+    expect(question, isNotNull);
+    expect(question.lexeme, "?");
+
+    PostfixExpression target = expression.target;
+    SimpleIdentifier identifier = target.operand;
+    expect(identifier.name, 'a');
+    expect(target.operator.lexeme, '!');
+  }
+
   void test_binary_expression_statement() {
     final unit = parseCompilationUnit('D? foo(X? x) { X ?? x2; }');
     FunctionDeclaration funct = unit.declarations[0];