From 5eb863698964b026149f4ed9f958639eb290f5b3 Mon Sep 17 00:00:00 2001
From: Urgau <urgau@numericable.fr>
Date: Wed, 16 Oct 2024 09:41:49 +0200
Subject: [PATCH] Handle gracefully true/false in `cfg(target(..))` compact

---
 compiler/rustc_attr/src/builtin.rs            | 8 +++++++-
 tests/ui/cfg/cfg-target-compact-errors.rs     | 4 ++++
 tests/ui/cfg/cfg-target-compact-errors.stderr | 8 +++++++-
 3 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/compiler/rustc_attr/src/builtin.rs b/compiler/rustc_attr/src/builtin.rs
index c1db4d07dfc..bbb17497684 100644
--- a/compiler/rustc_attr/src/builtin.rs
+++ b/compiler/rustc_attr/src/builtin.rs
@@ -723,7 +723,13 @@ pub fn eval_condition(
                     }
 
                     mis.iter().fold(true, |res, mi| {
-                        let mut mi = mi.meta_item().unwrap().clone();
+                        let Some(mut mi) = mi.meta_item().cloned() else {
+                            dcx.emit_err(session_diagnostics::CfgPredicateIdentifier {
+                                span: mi.span(),
+                            });
+                            return false;
+                        };
+
                         if let [seg, ..] = &mut mi.path.segments[..] {
                             seg.ident.name = Symbol::intern(&format!("target_{}", seg.ident.name));
                         }
diff --git a/tests/ui/cfg/cfg-target-compact-errors.rs b/tests/ui/cfg/cfg-target-compact-errors.rs
index daacbb2851d..e00d42fe4d9 100644
--- a/tests/ui/cfg/cfg-target-compact-errors.rs
+++ b/tests/ui/cfg/cfg-target-compact-errors.rs
@@ -14,4 +14,8 @@ fn two() {}
 //~^ ERROR invalid predicate `target_pointer`
 fn three() {}
 
+#[cfg(target(true))]
+//~^ ERROR `cfg` predicate key must be an identifier
+fn four() {}
+
 fn main() {}
diff --git a/tests/ui/cfg/cfg-target-compact-errors.stderr b/tests/ui/cfg/cfg-target-compact-errors.stderr
index bb858301eb5..219d9732c32 100644
--- a/tests/ui/cfg/cfg-target-compact-errors.stderr
+++ b/tests/ui/cfg/cfg-target-compact-errors.stderr
@@ -16,7 +16,13 @@ error[E0537]: invalid predicate `target_pointer`
 LL | #[cfg(target(os = "linux", pointer(width = "64")))]
    |                            ^^^^^^^^^^^^^^^^^^^^^
 
-error: aborting due to 3 previous errors
+error: `cfg` predicate key must be an identifier
+  --> $DIR/cfg-target-compact-errors.rs:17:14
+   |
+LL | #[cfg(target(true))]
+   |              ^^^^
+
+error: aborting due to 4 previous errors
 
 Some errors have detailed explanations: E0537, E0565.
 For more information about an error, try `rustc --explain E0537`.