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This macro has been superseded by the more recent `${concat(...)}`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, 1 insertions, 4 deletions

diff --git a/tests/ui/macros/macros-nonfatal-errors.rs b/tests/ui/macros/macros-nonfatal-errors.rs
index 091d64ea5d9..1349d741510 100644
--- a/tests/ui/macros/macros-nonfatal-errors.rs
+++ b/tests/ui/macros/macros-nonfatal-errors.rs
@@ -3,9 +3,8 @@
 // test that errors in a (selection) of macros don't kill compilation
 // immediately, so that we get more errors listed at a time.
 
-#![feature(trace_macros, concat_idents)]
+#![feature(trace_macros)]
 #![feature(stmt_expr_attributes)]
-#![expect(deprecated)] // concat_idents is deprecated
 
 use std::arch::asm;
 
@@ -105,8 +104,6 @@ fn main() {
     asm!(invalid); //~ ERROR
     llvm_asm!(invalid); //~ ERROR
 
-    concat_idents!("not", "idents"); //~ ERROR
-
     option_env!(invalid); //~ ERROR
     env!(invalid); //~ ERROR
     env!(foo, abr, baz); //~ ERROR