Suppress unused variable warning on variables used in group macro

    warning: variable `brace` is assigned to, but never used
       --> tests/test_meta.rs:168:17
        |
    168 |             let brace;
        |                 ^^^^^
        |
        = note: consider using `_brace` instead
        = note: `#[warn(unused_variables)]` (part of `#[warn(unused)]`) on by default

Author: dtolnay

src/group.rs

@@ -148,6 +148,7 @@ macro_rules! parenthesized {
         match $crate::__private::parse_parens(&$cursor) {
             $crate::__private::Ok(parens) => {
                 $content = parens.content;
+                _ = $content;
                 parens.token
             }
             $crate::__private::Err(error) => {
@@ -226,6 +227,7 @@ macro_rules! braced {
         match $crate::__private::parse_braces(&$cursor) {
             $crate::__private::Ok(braces) => {
                 $content = braces.content;
+                _ = $content;
                 braces.token
             }
             $crate::__private::Err(error) => {
@@ -281,6 +283,7 @@ macro_rules! bracketed {
         match $crate::__private::parse_brackets(&$cursor) {
             $crate::__private::Ok(brackets) => {
                 $content = brackets.content;
+                _ = $content;
                 brackets.token
             }
             $crate::__private::Err(error) => {