[gcc r14-11178] c++: ICE during requires-expr partial subst [PR118060]

[Patrick Palka via Gcc-cvs]

https://gcc.gnu.org/g:f73ecaf1957d35a99909999735ebe228c8dd6188

commit r14-11178-gf73ecaf1957d35a99909999735ebe228c8dd6188
Author: Patrick Palka <ppa...@redhat.com>
Date:   Thu Jan 9 10:50:19 2025 -0500

    c++: ICE during requires-expr partial subst [PR118060]
    
    Here during partial substitution of the requires-expression (as part of
    CTAD constraint rewriting) we segfault from the INDIRECT_REF case of
    convert_to_void due *f(u) being type-dependent.  We should just defer
    checking convert_to_void until satisfaction.
    
            PR c++/118060
    
    gcc/cp/ChangeLog:
    
            * constraint.cc (tsubst_valid_expression_requirement): Don't
            check convert_to_void during partial substitution.
    
    gcc/testsuite/ChangeLog:
    
            * g++.dg/cpp2a/concepts-requires40.C: New test.
    
    Reviewed-by: Jason Merrill <ja...@redhat.com>
    (cherry picked from commit ca79349c050c27ff466735ba78d2e2bbce56ffdc)

Diff:
---
 gcc/cp/constraint.cc                             |  4 +++-
 gcc/testsuite/g++.dg/cpp2a/concepts-requires40.C | 12 ++++++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/gcc/cp/constraint.cc b/gcc/cp/constraint.cc
index b6c6a5e23306..cbf6357ad681 100644
--- a/gcc/cp/constraint.cc
+++ b/gcc/cp/constraint.cc
@@ -1993,7 +1993,9 @@ tsubst_valid_expression_requirement (tree t, tree args, 
sat_info info)
 {
   tsubst_flags_t quiet = info.complain & ~tf_warning_or_error;
   tree r = tsubst_expr (t, args, quiet, info.in_decl);
-  if (convert_to_void (r, ICV_STATEMENT, quiet) != error_mark_node)
+  if (r != error_mark_node
+      && (processing_template_decl
+         || convert_to_void (r, ICV_STATEMENT, quiet) != error_mark_node))
     return r;
 
   if (info.diagnose_unsatisfaction_p ())
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-requires40.C 
b/gcc/testsuite/g++.dg/cpp2a/concepts-requires40.C
new file mode 100644
index 000000000000..918bab410f30
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-requires40.C
@@ -0,0 +1,12 @@
+// PR c++/118060
+// { dg-do compile { target c++20 } }
+
+int* f(int);
+
+template<class T>
+struct A {
+  template<class U> requires requires (U u) { *f(u); }
+  A(T, U);
+};
+
+A a{0, 0};