[COMMITTED 09/14] gccrs: fix cfg attribute error with literal predicate

[arthur . cohen]

From: Lucas Ly Ba <lucas.ly...@outlook.com>

gcc/rust/ChangeLog:

        * ast/rust-ast.cc (MetaItemLitExpr::check_cfg_predicate): Make error.

gcc/testsuite/ChangeLog:

        * rust/compile/issue-4222.rs: New test.

Signed-off-by: Lucas Ly Ba <lucas.ly...@outlook.com>
---
 gcc/rust/ast/rust-ast.cc                 | 3 +++
 gcc/testsuite/rust/compile/issue-4222.rs | 3 +++
 2 files changed, 6 insertions(+)
 create mode 100644 gcc/testsuite/rust/compile/issue-4222.rs

diff --git a/gcc/rust/ast/rust-ast.cc b/gcc/rust/ast/rust-ast.cc
index 7c6a1d215af..6d37ef7e22f 100644
--- a/gcc/rust/ast/rust-ast.cc
+++ b/gcc/rust/ast/rust-ast.cc
@@ -3834,6 +3834,9 @@ MetaItemLitExpr::check_cfg_predicate (const Session &) 
const
 {
   /* as far as I can tell, a literal expr can never be a valid cfg body, so
    * false */
+  rust_error_at (this->get_locus (), "'%s' predicate key cannot be a literal",
+                this->as_string ().c_str ());
+
   return false;
 }
 
diff --git a/gcc/testsuite/rust/compile/issue-4222.rs 
b/gcc/testsuite/rust/compile/issue-4222.rs
new file mode 100644
index 00000000000..b829c6f6f54
--- /dev/null
+++ b/gcc/testsuite/rust/compile/issue-4222.rs
@@ -0,0 +1,3 @@
+#![cfg(false)]
+// { dg-error ".false. predicate key cannot be a literal" "" { target *-*-* } 
.-1 }
+fn a() {}
-- 
2.50.1