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This macro has been superseded by the more recent `${concat(...)}`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

21 files changed, 53 insertions, 335 deletions

diff --git a/compiler/rustc_builtin_macros/messages.ftl b/compiler/rustc_builtin_macros/messages.ftl
index d32e6f1558e..bbf609a1b07 100644
--- a/compiler/rustc_builtin_macros/messages.ftl
+++ b/compiler/rustc_builtin_macros/messages.ftl
@@ -116,10 +116,6 @@ builtin_macros_concat_bytes_oob = numeric literal is out of bounds
 builtin_macros_concat_bytestr = cannot concatenate a byte string literal
 builtin_macros_concat_c_str_lit = cannot concatenate a C string literal
 
-builtin_macros_concat_idents_ident_args = `concat_idents!()` requires ident args
-
-builtin_macros_concat_idents_missing_args = `concat_idents!()` takes 1 or more arguments
-builtin_macros_concat_idents_missing_comma = `concat_idents!()` expecting comma
 builtin_macros_concat_missing_literal = expected a literal
     .note = only literals (like `"foo"`, `-42` and `3.14`) can be passed to `concat!()`
 
diff --git a/compiler/rustc_builtin_macros/src/concat_idents.rs b/compiler/rustc_builtin_macros/src/concat_idents.rs
deleted file mode 100644
index a721f5b84c5..00000000000
--- a/compiler/rustc_builtin_macros/src/concat_idents.rs
+++ /dev/null
@@ -1,71 +0,0 @@
-use rustc_ast::ptr::P;
-use rustc_ast::token::{self, Token};
-use rustc_ast::tokenstream::{TokenStream, TokenTree};
-use rustc_ast::{AttrVec, DUMMY_NODE_ID, Expr, ExprKind, Path, Ty, TyKind};
-use rustc_expand::base::{DummyResult, ExpandResult, ExtCtxt, MacResult, MacroExpanderResult};
-use rustc_span::{Ident, Span, Symbol};
-
-use crate::errors;
-
-pub(crate) fn expand_concat_idents<'cx>(
-    cx: &'cx mut ExtCtxt<'_>,
-    sp: Span,
-    tts: TokenStream,
-) -> MacroExpanderResult<'cx> {
-    if tts.is_empty() {
-        let guar = cx.dcx().emit_err(errors::ConcatIdentsMissingArgs { span: sp });
-        return ExpandResult::Ready(DummyResult::any(sp, guar));
-    }
-
-    let mut res_str = String::new();
-    for (i, e) in tts.iter().enumerate() {
-        if i & 1 == 1 {
-            match e {
-                TokenTree::Token(Token { kind: token::Comma, .. }, _) => {}
-                _ => {
-                    let guar = cx.dcx().emit_err(errors::ConcatIdentsMissingComma { span: sp });
-                    return ExpandResult::Ready(DummyResult::any(sp, guar));
-                }
-            }
-        } else {
-            if let TokenTree::Token(token, _) = e {
-                if let Some((ident, _)) = token.ident() {
-                    res_str.push_str(ident.name.as_str());
-                    continue;
-                }
-            }
-
-            let guar = cx.dcx().emit_err(errors::ConcatIdentsIdentArgs { span: sp });
-            return ExpandResult::Ready(DummyResult::any(sp, guar));
-        }
-    }
-
-    let ident = Ident::new(Symbol::intern(&res_str), cx.with_call_site_ctxt(sp));
-
-    struct ConcatIdentsResult {
-        ident: Ident,
-    }
-
-    impl MacResult for ConcatIdentsResult {
-        fn make_expr(self: Box<Self>) -> Option<P<Expr>> {
-            Some(P(Expr {
-                id: DUMMY_NODE_ID,
-                kind: ExprKind::Path(None, Path::from_ident(self.ident)),
-                span: self.ident.span,
-                attrs: AttrVec::new(),
-                tokens: None,
-            }))
-        }
-
-        fn make_ty(self: Box<Self>) -> Option<P<Ty>> {
-            Some(P(Ty {
-                id: DUMMY_NODE_ID,
-                kind: TyKind::Path(None, Path::from_ident(self.ident)),
-                span: self.ident.span,
-                tokens: None,
-            }))
-        }
-    }
-
-    ExpandResult::Ready(Box::new(ConcatIdentsResult { ident }))
-}
diff --git a/compiler/rustc_builtin_macros/src/errors.rs b/compiler/rustc_builtin_macros/src/errors.rs
index 3a2e96a5e5a..315257d606b 100644
--- a/compiler/rustc_builtin_macros/src/errors.rs
+++ b/compiler/rustc_builtin_macros/src/errors.rs
@@ -291,27 +291,6 @@ pub(crate) struct ConcatBytesBadRepeat {
 }
 
 #[derive(Diagnostic)]
-#[diag(builtin_macros_concat_idents_missing_args)]
-pub(crate) struct ConcatIdentsMissingArgs {
-    #[primary_span]
-    pub(crate) span: Span,
-}
-
-#[derive(Diagnostic)]
-#[diag(builtin_macros_concat_idents_missing_comma)]
-pub(crate) struct ConcatIdentsMissingComma {
-    #[primary_span]
-    pub(crate) span: Span,
-}
-
-#[derive(Diagnostic)]
-#[diag(builtin_macros_concat_idents_ident_args)]
-pub(crate) struct ConcatIdentsIdentArgs {
-    #[primary_span]
-    pub(crate) span: Span,
-}
-
-#[derive(Diagnostic)]
 #[diag(builtin_macros_bad_derive_target, code = E0774)]
 pub(crate) struct BadDeriveTarget {
     #[primary_span]
diff --git a/compiler/rustc_builtin_macros/src/lib.rs b/compiler/rustc_builtin_macros/src/lib.rs
index 9e7d0ec9e81..9b6dea21438 100644
--- a/compiler/rustc_builtin_macros/src/lib.rs
+++ b/compiler/rustc_builtin_macros/src/lib.rs
@@ -36,7 +36,6 @@ mod cfg_eval;
 mod compile_error;
 mod concat;
 mod concat_bytes;
-mod concat_idents;
 mod define_opaque;
 mod derive;
 mod deriving;
@@ -84,7 +83,6 @@ pub fn register_builtin_macros(resolver: &mut dyn ResolverExpand) {
         compile_error: compile_error::expand_compile_error,
         concat: concat::expand_concat,
         concat_bytes: concat_bytes::expand_concat_bytes,
-        concat_idents: concat_idents::expand_concat_idents,
         const_format_args: format::expand_format_args,
         core_panic: edition_panic::expand_panic,
         env: env::expand_env,
diff --git a/compiler/rustc_feature/src/removed.rs b/compiler/rustc_feature/src/removed.rs
index 0cd090b25a4..c54b831e244 100644
--- a/compiler/rustc_feature/src/removed.rs
+++ b/compiler/rustc_feature/src/removed.rs
@@ -285,4 +285,18 @@ declare_features! (
     // -------------------------------------------------------------------------
     // feature-group-end: removed features
     // -------------------------------------------------------------------------
+
+
+    // -------------------------------------------------------------------------
+    // feature-group-start: removed library features
+    // -------------------------------------------------------------------------
+    //
+    // FIXME(#141617): we should have a better way to track removed library features, but we reuse
+    // the infrastructure here so users still get hints. The symbols used here can be remove from
+    // `symbol.rs` when that happens.
+    (removed, concat_idents, "CURRENT_RUSTC_VERSION", Some(29599),
+     Some("use the `${concat(..)}` metavariable expression instead"), 142704),
+    // -------------------------------------------------------------------------
+    // feature-group-end: removed library features
+    // -------------------------------------------------------------------------
 );
diff --git a/library/core/src/macros/mod.rs b/library/core/src/macros/mod.rs
index b21845a1c16..b20ad8f92b1 100644
--- a/library/core/src/macros/mod.rs
+++ b/library/core/src/macros/mod.rs
@@ -1109,45 +1109,6 @@ pub(crate) mod builtin {
         ($name:expr $(,)?) => {{ /* compiler built-in */ }};
     }
 
-    /// Concatenates identifiers into one identifier.
-    ///
-    /// This macro takes any number of comma-separated identifiers, and
-    /// concatenates them all into one, yielding an expression which is a new
-    /// identifier. Note that hygiene makes it such that this macro cannot
-    /// capture local variables. Also, as a general rule, macros are only
-    /// allowed in item, statement or expression position. That means while
-    /// you may use this macro for referring to existing variables, functions or
-    /// modules etc, you cannot define a new one with it.
-    ///
-    /// # Examples
-    ///
-    /// ```
-    /// #![feature(concat_idents)]
-    ///
-    /// # fn main() {
-    /// fn foobar() -> u32 { 23 }
-    ///
-    /// let f = concat_idents!(foo, bar);
-    /// println!("{}", f());
-    ///
-    /// // fn concat_idents!(new, fun, name) { } // not usable in this way!
-    /// # }
-    /// ```
-    #[unstable(
-        feature = "concat_idents",
-        issue = "29599",
-        reason = "`concat_idents` is not stable enough for use and is subject to change"
-    )]
-    #[deprecated(
-        since = "1.88.0",
-        note = "use `${concat(...)}` with the `macro_metavar_expr_concat` feature instead"
-    )]
-    #[rustc_builtin_macro]
-    #[macro_export]
-    macro_rules! concat_idents {
-        ($($e:ident),+ $(,)?) => {{ /* compiler built-in */ }};
-    }
-
     /// Concatenates literals into a byte slice.
     ///
     /// This macro takes any number of comma-separated literals, and concatenates them all into
diff --git a/library/core/src/prelude/v1.rs b/library/core/src/prelude/v1.rs
index 8f1b5275871..7b9e04920d5 100644
--- a/library/core/src/prelude/v1.rs
+++ b/library/core/src/prelude/v1.rs
@@ -58,10 +58,9 @@ pub use crate::fmt::macros::Debug;
 pub use crate::hash::macros::Hash;
 
 #[stable(feature = "builtin_macro_prelude", since = "1.38.0")]
-#[allow(deprecated)]
 #[doc(no_inline)]
 pub use crate::{
-    assert, cfg, column, compile_error, concat, concat_idents, env, file, format_args,
+    assert, cfg, column, compile_error, concat, env, file, format_args,
     format_args_nl, include, include_bytes, include_str, line, log_syntax, module_path, option_env,
     stringify, trace_macros,
 };
diff --git a/library/std/src/lib.rs b/library/std/src/lib.rs
index 2bb7a63772d..13fb08a9210 100644
--- a/library/std/src/lib.rs
+++ b/library/std/src/lib.rs
@@ -281,7 +281,6 @@
 #![feature(cfg_target_thread_local)]
 #![feature(cfi_encoding)]
 #![feature(char_max_len)]
-#![feature(concat_idents)]
 #![feature(core_float_math)]
 #![feature(decl_macro)]
 #![feature(deprecated_suggestion)]
@@ -717,10 +716,9 @@ pub use core::primitive;
 pub use core::todo;
 // Re-export built-in macros defined through core.
 #[stable(feature = "builtin_macro_prelude", since = "1.38.0")]
-#[allow(deprecated)]
 pub use core::{
-    assert, assert_matches, cfg, column, compile_error, concat, concat_idents, const_format_args,
-    env, file, format_args, format_args_nl, include, include_bytes, include_str, line, log_syntax,
+    assert, assert_matches, cfg, column, compile_error, concat, const_format_args, env, file,
+    format_args, format_args_nl, include, include_bytes, include_str, line, log_syntax,
     module_path, option_env, stringify, trace_macros,
 };
 // Re-export macros defined in core.
diff --git a/library/std/src/prelude/v1.rs b/library/std/src/prelude/v1.rs
index c15d8c40085..69f03353153 100644
--- a/library/std/src/prelude/v1.rs
+++ b/library/std/src/prelude/v1.rs
@@ -45,10 +45,9 @@ pub use crate::result::Result::{self, Err, Ok};
 
 // Re-exported built-in macros
 #[stable(feature = "builtin_macro_prelude", since = "1.38.0")]
-#[allow(deprecated)]
 #[doc(no_inline)]
 pub use core::prelude::v1::{
-    assert, cfg, column, compile_error, concat, concat_idents, env, file, format_args,
+    assert, cfg, column, compile_error, concat, env, file, format_args,
     format_args_nl, include, include_bytes, include_str, line, log_syntax, module_path, option_env,
     stringify, trace_macros, Clone, Copy, Debug, Default, Eq, Hash, Ord, PartialEq, PartialOrd,
 };
diff --git a/src/doc/unstable-book/src/language-features/macro-metavar-expr-concat.md b/src/doc/unstable-book/src/language-features/macro-metavar-expr-concat.md
index b6dbdb14407..7eb5dca532f 100644
--- a/src/doc/unstable-book/src/language-features/macro-metavar-expr-concat.md
+++ b/src/doc/unstable-book/src/language-features/macro-metavar-expr-concat.md
@@ -8,7 +8,8 @@ In stable Rust, there is no way to create new identifiers by joining identifiers
  `#![feature(macro_metavar_expr_concat)]` introduces a way to do this, using the concat metavariable expression.
 
 > This feature uses the syntax from [`macro_metavar_expr`] but is otherwise
-> independent. It replaces the old unstable feature [`concat_idents`].
+> independent. It replaces the since-removed unstable feature
+> [`concat_idents`].
 
 > This is an experimental feature; it and its syntax will require a RFC before stabilization.
 
@@ -126,8 +127,7 @@ test result: ok. 6 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; fini
 
 [`paste`]: https://crates.io/crates/paste
 [RFC 3086]: https://rust-lang.github.io/rfcs/3086-macro-metavar-expr.html
-[`concat_idents!`]: https://doc.rust-lang.org/nightly/std/macro.concat_idents.html
 [`macro_metavar_expr`]: ../language-features/macro-metavar-expr.md
-[`concat_idents`]: ../library-features/concat-idents.md
+[`concat_idents`]: https://github.com/rust-lang/rust/issues/29599
 [#124225]: https://github.com/rust-lang/rust/issues/124225
 [declarative macros]: https://doc.rust-lang.org/stable/reference/macros-by-example.html
diff --git a/src/doc/unstable-book/src/library-features/concat-idents.md b/src/doc/unstable-book/src/library-features/concat-idents.md
deleted file mode 100644
index 8a38d155e3d..00000000000
--- a/src/doc/unstable-book/src/library-features/concat-idents.md
+++ /dev/null
@@ -1,27 +0,0 @@
-# `concat_idents`
-
-The tracking issue for this feature is: [#29599]
-
-This feature is deprecated, to be replaced by [`macro_metavar_expr_concat`].
-
-[#29599]: https://github.com/rust-lang/rust/issues/29599
-[`macro_metavar_expr_concat`]: https://github.com/rust-lang/rust/issues/124225
-
-------------------------
-
-> This feature is expected to be superseded by [`macro_metavar_expr_concat`](../language-features/macro-metavar-expr-concat.md).
-
-The `concat_idents` feature adds a macro for concatenating multiple identifiers
-into one identifier.
-
-## Examples
-
-```rust
-#![feature(concat_idents)]
-
-fn main() {
-    fn foobar() -> u32 { 23 }
-    let f = concat_idents!(foo, bar);
-    assert_eq!(f(), 23);
-}
-```
diff --git a/tests/ui/feature-gates/feature-gate-concat_idents.rs b/tests/ui/feature-gates/feature-gate-concat_idents.rs
deleted file mode 100644
index 4fc3b691597..00000000000
--- a/tests/ui/feature-gates/feature-gate-concat_idents.rs
+++ /dev/null
@@ -1,11 +0,0 @@
-#![expect(deprecated)] // concat_idents is deprecated
-
-const XY_1: i32 = 10;
-
-fn main() {
-    const XY_2: i32 = 20;
-    let a = concat_idents!(X, Y_1); //~ ERROR `concat_idents` is not stable
-    let b = concat_idents!(X, Y_2); //~ ERROR `concat_idents` is not stable
-    assert_eq!(a, 10);
-    assert_eq!(b, 20);
-}
diff --git a/tests/ui/feature-gates/feature-gate-concat_idents.stderr b/tests/ui/feature-gates/feature-gate-concat_idents.stderr
deleted file mode 100644
index 6399424eecd..00000000000
--- a/tests/ui/feature-gates/feature-gate-concat_idents.stderr
+++ /dev/null
@@ -1,23 +0,0 @@
-error[E0658]: use of unstable library feature `concat_idents`: `concat_idents` is not stable enough for use and is subject to change
-  --> $DIR/feature-gate-concat_idents.rs:7:13
-   |
-LL |     let a = concat_idents!(X, Y_1);
-   |             ^^^^^^^^^^^^^
-   |
-   = note: see issue #29599 <https://github.com/rust-lang/rust/issues/29599> for more information
-   = help: add `#![feature(concat_idents)]` to the crate attributes to enable
-   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
-
-error[E0658]: use of unstable library feature `concat_idents`: `concat_idents` is not stable enough for use and is subject to change
-  --> $DIR/feature-gate-concat_idents.rs:8:13
-   |
-LL |     let b = concat_idents!(X, Y_2);
-   |             ^^^^^^^^^^^^^
-   |
-   = note: see issue #29599 <https://github.com/rust-lang/rust/issues/29599> for more information
-   = help: add `#![feature(concat_idents)]` to the crate attributes to enable
-   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
-
-error: aborting due to 2 previous errors
-
-For more information about this error, try `rustc --explain E0658`.
diff --git a/tests/ui/feature-gates/feature-gate-concat_idents2.rs b/tests/ui/feature-gates/feature-gate-concat_idents2.rs
deleted file mode 100644
index bc2b4f7cddf..00000000000
--- a/tests/ui/feature-gates/feature-gate-concat_idents2.rs
+++ /dev/null
@@ -1,6 +0,0 @@
-#![expect(deprecated)] // concat_idents is deprecated
-
-fn main() {
-    concat_idents!(a, b); //~ ERROR `concat_idents` is not stable enough
-                          //~| ERROR cannot find value `ab` in this scope
-}
diff --git a/tests/ui/feature-gates/feature-gate-concat_idents2.stderr b/tests/ui/feature-gates/feature-gate-concat_idents2.stderr
deleted file mode 100644
index a770c1a348b..00000000000
--- a/tests/ui/feature-gates/feature-gate-concat_idents2.stderr
+++ /dev/null
@@ -1,20 +0,0 @@
-error[E0658]: use of unstable library feature `concat_idents`: `concat_idents` is not stable enough for use and is subject to change
-  --> $DIR/feature-gate-concat_idents2.rs:4:5
-   |
-LL |     concat_idents!(a, b);
-   |     ^^^^^^^^^^^^^
-   |
-   = note: see issue #29599 <https://github.com/rust-lang/rust/issues/29599> for more information
-   = help: add `#![feature(concat_idents)]` to the crate attributes to enable
-   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
-
-error[E0425]: cannot find value `ab` in this scope
-  --> $DIR/feature-gate-concat_idents2.rs:4:5
-   |
-LL |     concat_idents!(a, b);
-   |     ^^^^^^^^^^^^^^^^^^^^ not found in this scope
-
-error: aborting due to 2 previous errors
-
-Some errors have detailed explanations: E0425, E0658.
-For more information about an error, try `rustc --explain E0425`.
diff --git a/tests/ui/feature-gates/feature-gate-concat_idents3.rs b/tests/ui/feature-gates/feature-gate-concat_idents3.rs
deleted file mode 100644
index d4a0d2e6bb0..00000000000
--- a/tests/ui/feature-gates/feature-gate-concat_idents3.rs
+++ /dev/null
@@ -1,9 +0,0 @@
-#![expect(deprecated)] // concat_idents is deprecated
-
-const XY_1: i32 = 10;
-
-fn main() {
-    const XY_2: i32 = 20;
-    assert_eq!(10, concat_idents!(X, Y_1)); //~ ERROR `concat_idents` is not stable
-    assert_eq!(20, concat_idents!(X, Y_2)); //~ ERROR `concat_idents` is not stable
-}
diff --git a/tests/ui/feature-gates/feature-gate-concat_idents3.stderr b/tests/ui/feature-gates/feature-gate-concat_idents3.stderr
deleted file mode 100644
index 7d929322bc0..00000000000
--- a/tests/ui/feature-gates/feature-gate-concat_idents3.stderr
+++ /dev/null
@@ -1,23 +0,0 @@
-error[E0658]: use of unstable library feature `concat_idents`: `concat_idents` is not stable enough for use and is subject to change
-  --> $DIR/feature-gate-concat_idents3.rs:7:20
-   |
-LL |     assert_eq!(10, concat_idents!(X, Y_1));
-   |                    ^^^^^^^^^^^^^
-   |
-   = note: see issue #29599 <https://github.com/rust-lang/rust/issues/29599> for more information
-   = help: add `#![feature(concat_idents)]` to the crate attributes to enable
-   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
-
-error[E0658]: use of unstable library feature `concat_idents`: `concat_idents` is not stable enough for use and is subject to change
-  --> $DIR/feature-gate-concat_idents3.rs:8:20
-   |
-LL |     assert_eq!(20, concat_idents!(X, Y_2));
-   |                    ^^^^^^^^^^^^^
-   |
-   = note: see issue #29599 <https://github.com/rust-lang/rust/issues/29599> for more information
-   = help: add `#![feature(concat_idents)]` to the crate attributes to enable
-   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
-
-error: aborting due to 2 previous errors
-
-For more information about this error, try `rustc --explain E0658`.
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, );
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
diff --git a/tests/ui/macros/macros-nonfatal-errors.stderr b/tests/ui/macros/macros-nonfatal-errors.stderr
index 2f990cb24e2..bc34bd1c8ec 100644
--- a/tests/ui/macros/macros-nonfatal-errors.stderr
+++ b/tests/ui/macros/macros-nonfatal-errors.stderr
@@ -1,5 +1,5 @@
 error: the `#[default]` attribute may only be used on unit enum variants
-  --> $DIR/macros-nonfatal-errors.rs:14:5
+  --> $DIR/macros-nonfatal-errors.rs:13:5
    |
 LL |     #[default]
    |     ^^^^^^^^^^
@@ -7,7 +7,7 @@ LL |     #[default]
    = help: consider a manual implementation of `Default`
 
 error: the `#[default]` attribute may only be used on unit enum variants
-  --> $DIR/macros-nonfatal-errors.rs:19:36
+  --> $DIR/macros-nonfatal-errors.rs:18:36
    |
 LL | struct DefaultInnerAttrTupleStruct(#[default] ());
    |                                    ^^^^^^^^^^
@@ -15,7 +15,7 @@ LL | struct DefaultInnerAttrTupleStruct(#[default] ());
    = help: consider a manual implementation of `Default`
 
 error: the `#[default]` attribute may only be used on unit enum variants
-  --> $DIR/macros-nonfatal-errors.rs:23:1
+  --> $DIR/macros-nonfatal-errors.rs:22:1
    |
 LL | #[default]
    | ^^^^^^^^^^
@@ -23,7 +23,7 @@ LL | #[default]
    = help: consider a manual implementation of `Default`
 
 error: the `#[default]` attribute may only be used on unit enum variants
-  --> $DIR/macros-nonfatal-errors.rs:27:1
+  --> $DIR/macros-nonfatal-errors.rs:26:1
    |
 LL | #[default]
    | ^^^^^^^^^^
@@ -31,7 +31,7 @@ LL | #[default]
    = help: consider a manual implementation of `Default`
 
 error: the `#[default]` attribute may only be used on unit enum variants
-  --> $DIR/macros-nonfatal-errors.rs:37:11
+  --> $DIR/macros-nonfatal-errors.rs:36:11
    |
 LL |     Foo = #[default] 0,
    |           ^^^^^^^^^^
@@ -39,7 +39,7 @@ LL |     Foo = #[default] 0,
    = help: consider a manual implementation of `Default`
 
 error: the `#[default]` attribute may only be used on unit enum variants
-  --> $DIR/macros-nonfatal-errors.rs:38:14
+  --> $DIR/macros-nonfatal-errors.rs:37:14
    |
 LL |     Bar([u8; #[default] 1]),
    |              ^^^^^^^^^^
@@ -47,7 +47,7 @@ LL |     Bar([u8; #[default] 1]),
    = help: consider a manual implementation of `Default`
 
 error[E0665]: `#[derive(Default)]` on enum with no `#[default]`
-  --> $DIR/macros-nonfatal-errors.rs:43:10
+  --> $DIR/macros-nonfatal-errors.rs:42:10
    |
 LL |   #[derive(Default)]
    |            ^^^^^^^
@@ -67,7 +67,7 @@ LL |     #[default] Bar,
    |     ++++++++++
 
 error[E0665]: `#[derive(Default)]` on enum with no `#[default]`
-  --> $DIR/macros-nonfatal-errors.rs:49:10
+  --> $DIR/macros-nonfatal-errors.rs:48:10
    |
 LL |   #[derive(Default)]
    |            ^^^^^^^
@@ -78,7 +78,7 @@ LL | | }
    | |_- this enum needs a unit variant marked with `#[default]`
 
 error: multiple declared defaults
-  --> $DIR/macros-nonfatal-errors.rs:55:10
+  --> $DIR/macros-nonfatal-errors.rs:54:10
    |
 LL | #[derive(Default)]
    |          ^^^^^^^
@@ -95,7 +95,7 @@ LL |     Baz,
    = note: only one variant can be default
 
 error: `#[default]` attribute does not accept a value
-  --> $DIR/macros-nonfatal-errors.rs:67:5
+  --> $DIR/macros-nonfatal-errors.rs:66:5
    |
 LL |     #[default = 1]
    |     ^^^^^^^^^^^^^^
@@ -103,7 +103,7 @@ LL |     #[default = 1]
    = help: try using `#[default]`
 
 error: multiple `#[default]` attributes
-  --> $DIR/macros-nonfatal-errors.rs:75:5
+  --> $DIR/macros-nonfatal-errors.rs:74:5
    |
 LL |     #[default]
    |     ---------- `#[default]` used here
@@ -114,13 +114,13 @@ LL |     Foo,
    |
    = note: only one `#[default]` attribute is needed
 help: try removing this
-  --> $DIR/macros-nonfatal-errors.rs:74:5
+  --> $DIR/macros-nonfatal-errors.rs:73:5
    |
 LL |     #[default]
    |     ^^^^^^^^^^
 
 error: multiple `#[default]` attributes
-  --> $DIR/macros-nonfatal-errors.rs:85:5
+  --> $DIR/macros-nonfatal-errors.rs:84:5
    |
 LL |     #[default]
    |     ---------- `#[default]` used here
@@ -132,7 +132,7 @@ LL |     Foo,
    |
    = note: only one `#[default]` attribute is needed
 help: try removing these
-  --> $DIR/macros-nonfatal-errors.rs:82:5
+  --> $DIR/macros-nonfatal-errors.rs:81:5
    |
 LL |     #[default]
    |     ^^^^^^^^^^
@@ -142,7 +142,7 @@ LL |     #[default]
    |     ^^^^^^^^^^
 
 error: the `#[default]` attribute may only be used on unit enum variants
-  --> $DIR/macros-nonfatal-errors.rs:92:5
+  --> $DIR/macros-nonfatal-errors.rs:91:5
    |
 LL |     Foo {},
    |     ^^^
@@ -150,7 +150,7 @@ LL |     Foo {},
    = help: consider a manual implementation of `Default`
 
 error: default variant must be exhaustive
-  --> $DIR/macros-nonfatal-errors.rs:100:5
+  --> $DIR/macros-nonfatal-errors.rs:99:5
    |
 LL |     #[non_exhaustive]
    |     ----------------- declared `#[non_exhaustive]` here
@@ -160,37 +160,31 @@ LL |     Foo,
    = help: consider a manual implementation of `Default`
 
 error: asm template must be a string literal
-  --> $DIR/macros-nonfatal-errors.rs:105:10
+  --> $DIR/macros-nonfatal-errors.rs:104:10
    |
 LL |     asm!(invalid);
    |          ^^^^^^^
 
-error: `concat_idents!()` requires ident args
-  --> $DIR/macros-nonfatal-errors.rs:108:5
-   |
-LL |     concat_idents!("not", "idents");
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
 error: argument must be a string literal
-  --> $DIR/macros-nonfatal-errors.rs:110:17
+  --> $DIR/macros-nonfatal-errors.rs:107:17
    |
 LL |     option_env!(invalid);
    |                 ^^^^^^^
 
 error: expected string literal
-  --> $DIR/macros-nonfatal-errors.rs:111:10
+  --> $DIR/macros-nonfatal-errors.rs:108:10
    |
 LL |     env!(invalid);
    |          ^^^^^^^
 
 error: `env!()` takes 1 or 2 arguments
-  --> $DIR/macros-nonfatal-errors.rs:112:5
+  --> $DIR/macros-nonfatal-errors.rs:109:5
    |
 LL |     env!(foo, abr, baz);
    |     ^^^^^^^^^^^^^^^^^^^
 
 error: environment variable `RUST_HOPEFULLY_THIS_DOESNT_EXIST` not defined at compile time
-  --> $DIR/macros-nonfatal-errors.rs:113:5
+  --> $DIR/macros-nonfatal-errors.rs:110:5
    |
 LL |     env!("RUST_HOPEFULLY_THIS_DOESNT_EXIST");
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -198,7 +192,7 @@ LL |     env!("RUST_HOPEFULLY_THIS_DOESNT_EXIST");
    = help: use `std::env::var("RUST_HOPEFULLY_THIS_DOESNT_EXIST")` to read the variable at run time
 
 error: format argument must be a string literal
-  --> $DIR/macros-nonfatal-errors.rs:115:13
+  --> $DIR/macros-nonfatal-errors.rs:112:13
    |
 LL |     format!(invalid);
    |             ^^^^^^^
@@ -209,43 +203,43 @@ LL |     format!("{}", invalid);
    |             +++++
 
 error: argument must be a string literal
-  --> $DIR/macros-nonfatal-errors.rs:117:14
+  --> $DIR/macros-nonfatal-errors.rs:114:14
    |
 LL |     include!(invalid);
    |              ^^^^^^^
 
 error: argument must be a string literal
-  --> $DIR/macros-nonfatal-errors.rs:119:18
+  --> $DIR/macros-nonfatal-errors.rs:116:18
    |
 LL |     include_str!(invalid);
    |                  ^^^^^^^
 
 error: couldn't read `$DIR/i'd be quite surprised if a file with this name existed`: $FILE_NOT_FOUND_MSG
-  --> $DIR/macros-nonfatal-errors.rs:120:5
+  --> $DIR/macros-nonfatal-errors.rs:117:5
    |
 LL |     include_str!("i'd be quite surprised if a file with this name existed");
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: argument must be a string literal
-  --> $DIR/macros-nonfatal-errors.rs:121:20
+  --> $DIR/macros-nonfatal-errors.rs:118:20
    |
 LL |     include_bytes!(invalid);
    |                    ^^^^^^^
 
 error: couldn't read `$DIR/i'd be quite surprised if a file with this name existed`: $FILE_NOT_FOUND_MSG
-  --> $DIR/macros-nonfatal-errors.rs:122:5
+  --> $DIR/macros-nonfatal-errors.rs:119:5
    |
 LL |     include_bytes!("i'd be quite surprised if a file with this name existed");
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: trace_macros! accepts only `true` or `false`
-  --> $DIR/macros-nonfatal-errors.rs:124:5
+  --> $DIR/macros-nonfatal-errors.rs:121:5
    |
 LL |     trace_macros!(invalid);
    |     ^^^^^^^^^^^^^^^^^^^^^^
 
 error: default variant must be exhaustive
-  --> $DIR/macros-nonfatal-errors.rs:134:9
+  --> $DIR/macros-nonfatal-errors.rs:131:9
    |
 LL |         #[non_exhaustive]
    |         ----------------- declared `#[non_exhaustive]` here
@@ -255,11 +249,11 @@ LL |         Foo,
    = help: consider a manual implementation of `Default`
 
 error: cannot find macro `llvm_asm` in this scope
-  --> $DIR/macros-nonfatal-errors.rs:106:5
+  --> $DIR/macros-nonfatal-errors.rs:105:5
    |
 LL |     llvm_asm!(invalid);
    |     ^^^^^^^^
 
-error: aborting due to 29 previous errors
+error: aborting due to 28 previous errors
 
 For more information about this error, try `rustc --explain E0665`.
diff --git a/tests/ui/syntax-extension-minor.rs b/tests/ui/syntax-extension-minor.rs
deleted file mode 100644
index 826990a89a5..00000000000
--- a/tests/ui/syntax-extension-minor.rs
+++ /dev/null
@@ -1,15 +0,0 @@
-//@ run-pass
-
-#![feature(concat_idents)]
-#![expect(deprecated)] // concat_idents is deprecated
-
-pub fn main() {
-    struct Foo;
-    let _: concat_idents!(F, oo) = Foo; // Test that `concat_idents!` can be used in type positions
-
-    let asdf_fdsa = "<.<".to_string();
-    // concat_idents should have call-site hygiene.
-    assert!(concat_idents!(asd, f_f, dsa) == "<.<".to_string());
-
-    assert_eq!(stringify!(use_mention_distinction), "use_mention_distinction");
-}