fixup! test: cross-edition metavar fragment specifiers

Signed-off-by: Vincenzo Palazzo <vincenzopalazzodev@gmail.com>

tests/ui/macros/auxiliary/metavar_2021.rs

@@ -1,16 +1,12 @@
 //@ edition: 2021
-
-#![feature(macro_metavar_expr)]
-
 #[macro_export]
 macro_rules! make_matcher {
-    ($name:ident, $fragment_type:ident) => {
+    ($name:ident, $fragment_type:ident, $d:tt) => {
         #[macro_export]
         macro_rules! $name {
-            ($$_:$fragment_type) => { true };
-            ($$($$_:tt)*) => { false };
+            ($d _:$fragment_type) => { true };
+            (const { 0 }) => { false };
         }
-    }
+    };
 }
-
-make_matcher!(is_expr_from_2021, expr);
+make_matcher!(is_expr_from_2021, expr, $);

tests/ui/macros/expr_2021_with_metavar_expr.rs

@@ -2,7 +2,8 @@
 //@ aux-build: metavar_2021.rs
 //@ run-pass
 
-// This test captures the behavior of macro-generating-macros with fragment specifiers across edition b
+// This test captures the behavior of macro-generating-macros with fragment
+// specifiers across edition boundaries.
 
 #![feature(expr_fragment_specifier_2024)]
 #![feature(macro_metavar_expr)]
@@ -12,7 +13,7 @@ extern crate metavar_2021;
 
 use metavar_2021::{is_expr_from_2021, make_matcher};
 
-make_matcher!(is_expr_from_2024, expr);
+make_matcher!(is_expr_from_2024, expr, $);
 
 fn main() {
     let from_2021 = is_expr_from_2021!(const { 0 });
@@ -21,9 +22,7 @@ fn main() {
     dbg!(from_2024);
 
     // These capture the current, empirically determined behavior.
-    //
-    // It's not clear whether this is the desired behavior, but that's a
-    // question we can deal with when stabilizing macro_metavar_expr.
+    // It's not clear whether this is the desired behavior.
     assert!(!from_2021);
     assert!(!from_2024);
 }