Remove the deprecated `concat_idents!` macro

In [137653], the lang and libs-API teams did a joint FCP to deprecate
and eventually remove the long-unstable `concat_idents!` macro. The
deprecation is landing in 1.88, so do the removal here (target version
1.90).

This macro has been superseded by the more recent `${concat(...)}`
metavariable expression language feature, which avoids some of the
limitations of `concat_idents!`. The metavar expression is unstably
available under the [`macro_metavar_expr_concat`] feature.

History is mildly interesting here: `concat_idents!` goes back to 2011
when it was introduced with 513276e595f8 ("Add #concat_idents[] and
about the same:

    let asdf_fdsa = "<.<";
    assert(#concat_idents[asd,f_f,dsa] == "<.<");

    assert(#ident_to_str[use_mention_distinction]
           == "use_mention_distinction");

(That test existed from introduction until its removal here.)

Closes: https://www.github.com/rust-lang/rust/issues/29599

[137653]: https://www.github.com/rust-lang/rust/pull/137653
[`macro_metavar_expr_concat`]: https://www.github.com/rust-lang/rust/issues/124225

1 files changed, 0 insertions, 12 deletions

diff --git a/tests/ui/macros/macro-comma-support-rpass.rs b/tests/ui/macros/macro-comma-support-rpass.rs
index 5a4bac70b1c..ef6c1ff6fd0 100644
--- a/tests/ui/macros/macro-comma-support-rpass.rs
+++ b/tests/ui/macros/macro-comma-support-rpass.rs
@@ -15,7 +15,6 @@
 #![cfg_attr(core, no_std)]
 
 #![allow(deprecated)] // for deprecated `try!()` macro
-#![feature(concat_idents)]
 
 #[cfg(std)] use std::fmt;
 #[cfg(core)] use core::fmt;
@@ -80,17 +79,6 @@ fn concat() {
 }
 
 #[test]
-fn concat_idents() {
-    fn foo() {}
-    fn foobar() {}
-
-    concat_idents!(foo)();
-    concat_idents!(foo,)();
-    concat_idents!(foo, bar)();
-    concat_idents!(foo, bar,)();
-}
-
-#[test]
 fn debug_assert() {
     debug_assert!(true);
     debug_assert!(true, );