Ignore unused_macro_rules warning in test macros

    warning: 2nd rule of macro `snapshot_impl` is never used
      --> tests/macros/mod.rs:44:5
       |
    44 |     (($($expr:tt)*) as $t:ty, @$snapshot:literal) => {{
       |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
       |
       = note: `#[warn(unused_macro_rules)]` on by default

    warning: 1st rule of macro `snapshot_impl` is never used
      --> tests/macros/mod.rs:37:5
       |
    37 |     (($expr:ident) as $t:ty, @$snapshot:literal) => {
       |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

    warning: 3rd rule of macro `snapshot_impl` is never used
      --> tests/macros/mod.rs:52:5
       |
    52 |     (($($expr:tt)*) , @$snapshot:literal) => {{
       |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

    warning: 2nd rule of macro `spanless_eq_enum` is never used
       --> tests/common/eq.rs:225:5
        |
    225 | /     {
    226 | |         $($name:ident)::+;
    227 | |         $([$($variant:ident)::+; $($fields:tt)*])*
    228 | |         $next:ident [$([$($named:tt)*])* $(![$ignore:tt])*] (!$i:tt $($field:tt)*)
    229 | |         $($rest:tt)*
    230 | |     } => {
        | |_____^
        |
        = note: `#[warn(unused_macro_rules)]` on by default

tests/common/eq.rs

@@ -1,3 +1,5 @@
+#![allow(unused_macro_rules)]
+
 extern crate rustc_ast;
 extern crate rustc_data_structures;
 extern crate rustc_span;

tests/macros/mod.rs

@@ -1,4 +1,4 @@
-#![allow(unused_macros)]
+#![allow(unused_macros, unused_macro_rules)]
 
 #[path = "../debug/mod.rs"]
 pub mod debug;