fixup! Remove the deprecated concat_idents! macro

Author: tgross35

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
+    // -------------------------------------------------------------------------
 );

compiler/rustc_span/src/symbol.rs

@@ -684,6 +684,7 @@ symbols! {
         compiler_fence,
         concat,
         concat_bytes,
+        concat_idents,
         conservative_impl_trait,
         console,
         const_allocate,

library/core/src/prelude/v1.rs

@@ -60,7 +60,7 @@ pub use crate::hash::macros::Hash;
 #[stable(feature = "builtin_macro_prelude", since = "1.38.0")]
 #[doc(no_inline)]
 pub use crate::{
-    assert, cfg, column, compile_error, concat,  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,
 };

tests/ui/unpretty/exhaustive.expanded.stdout

@@ -620,7 +620,12 @@ mod types {
         /*! there is no syntax for this */
     }
     /// TyKind::MacCall
-    fn ty_mac_call() { let _ = "T"; let _ = "T"; let _ = "T"; }
+    fn ty_mac_call() {
+        macro_rules! ty { ($ty:ty) => { $ty } }
+        let _: T;
+        let _: T;
+        let _: T;
+    }
     /// TyKind::CVarArgs
     fn ty_c_var_args() {
         /*! FIXME: todo */

tests/ui/unpretty/exhaustive.hir.stdout

@@ -694,7 +694,12 @@ mod types {
     /*! there is no syntax for this */
     fn ty_implicit_self() { }
     /// TyKind::MacCall
-    fn ty_mac_call() { let _ = "T"; let _ = "T"; let _ = "T"; }
+    fn ty_mac_call() {
+        macro_rules! ty { ($ty:ty) => { $ty } }
+        let _: T;
+        let _: T;
+        let _: T;
+    }
     /// TyKind::CVarArgs
     /*! FIXME: todo */
     fn ty_c_var_args() { }

tests/ui/unpretty/exhaustive.rs

@@ -835,9 +835,12 @@ mod types {
 
     /// TyKind::MacCall
     fn ty_mac_call() {
-        let _ = concat!("T");
-        let _ = concat!["T"];
-        let _ = concat! { "T" };
+        macro_rules! ty {
+            ($ty:ty) => { $ty }
+        }
+        let _: ty!(T);
+        let _: ty![T];
+        let _: ty! { T };
     }
 
     /// TyKind::CVarArgs