Rollup merge of rust-lang#95764 - c410-f3r:metavar-test, r=petrochenkov

[macro_metavar_expr] Add tests to ensure the feature requirement

These tests should have been added in the initial implementation they were unintentionally forgotten

cc rust-lang#83527
r? ```@petrochenkov```

Author: Dylan-DPC

src/test/ui/macros/rfc-3086-metavar-expr/required-feature.rs

@@ -5,5 +5,40 @@ macro_rules! count {
     };
 }
 
+macro_rules! dollar_dollar {
+    () => {
+        macro_rules! bar {
+            ( $$( $$any:tt )* ) => { $$( $$any )* };
+            //~^ ERROR meta-variable expressions are unstable
+            //~| ERROR meta-variable expressions are unstable
+            //~| ERROR meta-variable expressions are unstable
+            //~| ERROR meta-variable expressions are unstable
+        }
+    };
+}
+
+macro_rules! index {
+    ( $( $e:stmt ),* ) => {
+        $( ${ignore(e)} ${index()} )*
+        //~^ ERROR meta-variable expressions are unstable
+        //~| ERROR meta-variable expressions are unstable
+    };
+}
+
+macro_rules! ignore {
+    ( $( $i:stmt ),* ) => {{
+        0 $( + 1 ${ignore(i)} )*
+        //~^ ERROR meta-variable expressions are unstable
+    }};
+}
+
+macro_rules! length {
+    ( $( $e:stmt ),* ) => {
+        $( ${ignore(e)} ${length()} )*
+        //~^ ERROR meta-variable expressions are unstable
+        //~| ERROR meta-variable expressions are unstable
+    };
+}
+
 fn main() {
 }

src/test/ui/macros/rfc-3086-metavar-expr/required-feature.stderr

@@ -7,6 +7,87 @@ LL |         ${ count(e) }
    = note: see issue #83527 <https://github.com/rust-lang/rust/issues/83527> for more information
    = help: add `#![feature(macro_metavar_expr)]` to the crate attributes to enable
 
-error: aborting due to previous error
+error[E0658]: meta-variable expressions are unstable
+  --> $DIR/required-feature.rs:11:16
+   |
+LL |             ( $$( $$any:tt )* ) => { $$( $$any )* };
+   |                ^
+   |
+   = note: see issue #83527 <https://github.com/rust-lang/rust/issues/83527> for more information
+   = help: add `#![feature(macro_metavar_expr)]` to the crate attributes to enable
+
+error[E0658]: meta-variable expressions are unstable
+  --> $DIR/required-feature.rs:11:20
+   |
+LL |             ( $$( $$any:tt )* ) => { $$( $$any )* };
+   |                    ^
+   |
+   = note: see issue #83527 <https://github.com/rust-lang/rust/issues/83527> for more information
+   = help: add `#![feature(macro_metavar_expr)]` to the crate attributes to enable
+
+error[E0658]: meta-variable expressions are unstable
+  --> $DIR/required-feature.rs:11:39
+   |
+LL |             ( $$( $$any:tt )* ) => { $$( $$any )* };
+   |                                       ^
+   |
+   = note: see issue #83527 <https://github.com/rust-lang/rust/issues/83527> for more information
+   = help: add `#![feature(macro_metavar_expr)]` to the crate attributes to enable
+
+error[E0658]: meta-variable expressions are unstable
+  --> $DIR/required-feature.rs:11:43
+   |
+LL |             ( $$( $$any:tt )* ) => { $$( $$any )* };
+   |                                           ^
+   |
+   = note: see issue #83527 <https://github.com/rust-lang/rust/issues/83527> for more information
+   = help: add `#![feature(macro_metavar_expr)]` to the crate attributes to enable
+
+error[E0658]: meta-variable expressions are unstable
+  --> $DIR/required-feature.rs:22:13
+   |
+LL |         $( ${ignore(e)} ${index()} )*
+   |             ^^^^^^^^^^^
+   |
+   = note: see issue #83527 <https://github.com/rust-lang/rust/issues/83527> for more information
+   = help: add `#![feature(macro_metavar_expr)]` to the crate attributes to enable
+
+error[E0658]: meta-variable expressions are unstable
+  --> $DIR/required-feature.rs:22:26
+   |
+LL |         $( ${ignore(e)} ${index()} )*
+   |                          ^^^^^^^^^
+   |
+   = note: see issue #83527 <https://github.com/rust-lang/rust/issues/83527> for more information
+   = help: add `#![feature(macro_metavar_expr)]` to the crate attributes to enable
+
+error[E0658]: meta-variable expressions are unstable
+  --> $DIR/required-feature.rs:30:19
+   |
+LL |         0 $( + 1 ${ignore(i)} )*
+   |                   ^^^^^^^^^^^
+   |
+   = note: see issue #83527 <https://github.com/rust-lang/rust/issues/83527> for more information
+   = help: add `#![feature(macro_metavar_expr)]` to the crate attributes to enable
+
+error[E0658]: meta-variable expressions are unstable
+  --> $DIR/required-feature.rs:37:13
+   |
+LL |         $( ${ignore(e)} ${length()} )*
+   |             ^^^^^^^^^^^
+   |
+   = note: see issue #83527 <https://github.com/rust-lang/rust/issues/83527> for more information
+   = help: add `#![feature(macro_metavar_expr)]` to the crate attributes to enable
+
+error[E0658]: meta-variable expressions are unstable
+  --> $DIR/required-feature.rs:37:26
+   |
+LL |         $( ${ignore(e)} ${length()} )*
+   |                          ^^^^^^^^^^
+   |
+   = note: see issue #83527 <https://github.com/rust-lang/rust/issues/83527> for more information
+   = help: add `#![feature(macro_metavar_expr)]` to the crate attributes to enable
+
+error: aborting due to 10 previous errors
 
 For more information about this error, try `rustc --explain E0658`.