Fixes #2838. Variable named _ does not bind anything

Language/Expressions/Identifier_Reference/syntax_t01.dart

@@ -35,8 +35,6 @@
 /// ;
 /// @description Checks various identifiers.
 /// @author msyabro
-/// @reviewer kaigorodov
-
 
 main() {
   var x, _x, $x, x1y2, $$$, _12, ___, $, _, $1_;
@@ -46,7 +44,6 @@ main() {
   x1y2;
   $$$;
   _12;
-  _;
   $;
   ___;
   $1_;

Language/Functions/Formal_Parameters/Optional_Formals/name_t01.dart

@@ -21,5 +21,8 @@ main() {
 // [cfe] unspecified
 
   f1(_: 1);
+//   ^
+// [analyzer] unspecified
+// [cfe] unspecified
   f2();
 }

Language/Functions/Formal_Parameters/Optional_Formals/name_t02.dart

@@ -30,4 +30,7 @@ class C {
 main() {
   new A(_p: "Optional parameter names must not begin with an underscore!");
   new C(_: "Optional parameter names must not begin with an underscore!");
+//      ^
+// [analyzer] unspecified
+// [cfe] unspecified
 }

Language/Overview/Privacy/private_and_public_t14.dart

@@ -17,15 +17,15 @@
 import "../../../Utils/expect.dart";
 
 class A {
-  fun(_, _$, ___) {return _ + _$ + ___;}
-  static staticfun(_, _$, __) {return _ + _$ + __;}
+  fun(_x, _$, ___) {return _x + _$ + ___;}
+  static staticfun(_x, _$, __) {return _x + _$ + __;}
 
   var _check;
   var __;
-  A(_, _$, this.__) : _check = _ + _$ {}
-  A.named(_, _$, ___) : _check = _ + _$ + ___ {}
+  A(_x, _$, this.__) : _check = _x + _$ {}
+  A.named(_x, _$, ___) : _check = _x + _$ + ___ {}
 
-  void set _setter(_) {__ = _;}
+  void set _setter(_x) {__ = _x;}
 }
 
 

Language/Overview/Privacy/private_and_public_t15.dart

@@ -14,15 +14,14 @@
 /// and are still accessible in the appropriate scope.
 /// @author iefremov
 
-
-class G<_, _$, __> {
-  _? x = null;
+class G<_x, _$, __> {
+  _x? x = null;
   _$? y = null;
   __? z;
 }
 
 class G2<A, B, C> extends G<A, B, C> {}
-class G3<_> extends G<_, _, _>{}
+class G3<_X> extends G<_X, _X, _X>{}
 
 main() {
   new G<int, String, double>();

LanguageFeatures/Patterns/pattern_context_A06_t03.dart

@@ -6,15 +6,16 @@
 /// A simple identifier in any context named _ is treated as a wildcard variable
 /// pattern.
 ///
-/// @description Checks that a simple identifier in aa assignment context named
-/// _ is treated as a wildcard variable pattern.
+/// @description Checks that a simple identifier in an assignment context named
+/// `_` is treated as a wildcard variable pattern.
 /// @author [email protected]
 
 import "../../Utils/expect.dart";
 import "patterns_lib.dart";
 
+int _ = 0;
+
 main() {
-  int _ = 0;
   int a = 0;
   String s = "";
 

LanguageFeatures/Wildcards/binding_A01_t13.dart

@@ -0,0 +1,27 @@
+// Copyright (c) 2024, 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.
+
+/// @assertion A local declaration whose name is `_` does not bind that name to
+/// anything.
+///
+/// @description Checks that an identifier reference of the form `_` in a string
+/// literal does not resolve to a local variable which is a wildcard since there
+/// is no such binding.
+/// @author [email protected]
+
+// SharedOptions=--enable-experiment=wildcard-variables
+
+main() {
+  var _ = "Wildcard";
+
+  print("$_");
+//        ^
+// [analyzer] unspecified
+// [cfe] unspecified
+
+  print("${_}");
+//         ^
+// [analyzer] unspecified
+// [cfe] unspecified
+}