[PATCH] c++/reflection: fix crash with substitute [PR124204]

[Marek Polacek]

Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?

-- >8 --
Here we crash in implicit_conversion on:

  /* An argument should have gone through convert_from_reference.  */
  gcc_checking_assert (!expr || !TYPE_REF_P (from));

so let's do that.

        PR c++/124204

gcc/cp/ChangeLog:

        * reflect.cc (eval_can_substitute): Call convert_from_reference.

gcc/testsuite/ChangeLog:

        * g++.dg/reflect/substitute5.C: New test.
---
 gcc/cp/reflect.cc                          |  1 +
 gcc/testsuite/g++.dg/reflect/substitute5.C | 11 +++++++++++
 2 files changed, 12 insertions(+)
 create mode 100644 gcc/testsuite/g++.dg/reflect/substitute5.C

diff --git a/gcc/cp/reflect.cc b/gcc/cp/reflect.cc
index 522b7c06a29..7f23784be5d 100644
--- a/gcc/cp/reflect.cc
+++ b/gcc/cp/reflect.cc
@@ -5318,6 +5318,7 @@ eval_can_substitute (location_t loc, const constexpr_ctx 
*ctx,
                                "invalid argument to can_substitute",
                                fun, non_constant_p, jump_target);
       a = resolve_nondeduced_context (a, tf_warning_or_error);
+      a = convert_from_reference (a);
       TREE_VEC_ELT (rvec, i) = a;
     }
   if (DECL_TYPE_TEMPLATE_P (r) || DECL_TEMPLATE_TEMPLATE_PARM_P (r))
diff --git a/gcc/testsuite/g++.dg/reflect/substitute5.C 
b/gcc/testsuite/g++.dg/reflect/substitute5.C
new file mode 100644
index 00000000000..f9af9bf5f46
--- /dev/null
+++ b/gcc/testsuite/g++.dg/reflect/substitute5.C
@@ -0,0 +1,11 @@
+// PR c++/124204
+// { dg-do compile { target c++26 } }
+// { dg-additional-options "-freflection" }
+
+#include <meta>
+
+template<int>
+using U = void;
+constexpr int v = 0;
+constexpr auto &ref = v;
+constexpr auto result = substitute(^^U, {^^ref});

base-commit: 4cd4ec9bd3de347fbd112d2762e05a607243253c
-- 
2.53.0