[gcc r15-8005] c++: ICE with lambda in fold expression in requires [PR119134]

[Marek Polacek]

https://gcc.gnu.org/g:0e47062ce70d147091f1a97ec94bd6efad92bc5e

commit r15-8005-g0e47062ce70d147091f1a97ec94bd6efad92bc5e
Author: Marek Polacek <polacek@redhat.com>
Date:   Fri Mar 7 11:26:46 2025 -0500

    c++: ICE with lambda in fold expression in requires [PR119134]
    
    The r12-8258 fix assumes that DECL_CONTEXT of 'pack' in
    check_for_bare_parameter_packs is going to be an operator()
    but as this test shows, it can be empty.
    
            PR c++/119134
    
    gcc/cp/ChangeLog:
    
            * pt.cc (check_for_bare_parameter_packs): Check DECL_CONTEXT.
    
    gcc/testsuite/ChangeLog:
    
            * g++.dg/cpp2a/lambda-uneval24.C: New test.
    
    Reviewed-by: Jason Merrill <jason@redhat.com>

Diff:
---
 gcc/cp/pt.cc                                 | 1 +
 gcc/testsuite/g++.dg/cpp2a/lambda-uneval24.C | 4 ++++
 2 files changed, 5 insertions(+)

diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 6ac9e6f163ec..8aaae4468687 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -4375,6 +4375,7 @@ check_for_bare_parameter_packs (tree t, location_t loc /* = UNKNOWN_LOCATION */)
 	tree pack = TREE_VALUE (parameter_packs);
 	if (is_capture_proxy (pack)
 	    || (TREE_CODE (pack) == PARM_DECL
+		&& DECL_CONTEXT (pack)
 		&& DECL_CONTEXT (DECL_CONTEXT (pack)) == lam))
 	  break;
       }
diff --git a/gcc/testsuite/g++.dg/cpp2a/lambda-uneval24.C b/gcc/testsuite/g++.dg/cpp2a/lambda-uneval24.C
new file mode 100644
index 000000000000..a2b45595e479
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/lambda-uneval24.C
@@ -0,0 +1,4 @@
+// PR c++/119134
+// { dg-do compile { target c++20 } }
+
+void f(auto... args) requires(([args] {}, ..., true)) {}