When cp_unevaluated_operand is set, tsubst_decl thinks that if it sees a
PARM_DECL that isn't already in local_specializations, we're in a decltype
in a trailing return type or some such, and so we only want a substitution
for a single PARM_DECL. In this case, we want the whole chain, so make sure
cp_unevaluated_operand is cleared.
Tested x86_64-pc-linux-gnu, applying to 8/9/10.
gcc/cp/ChangeLog
2020-03-14 Jason Merrill <ja...@redhat.com>
PR c++/93248
* pt.c (build_deduction_guide): Clear cp_unevaluated_operand for
substituting DECL_ARGUMENTS.
---
gcc/cp/pt.c | 5 ++++-
gcc/testsuite/g++.dg/cpp1z/class-deduction71.C | 6 ++++++
2 files changed, 10 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/g++.dg/cpp1z/class-deduction71.C
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 789ccdbbbd1..0f3c2ad8fec 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -28071,10 +28071,13 @@ build_deduction_guide (tree type, tree ctor, tree
outer_args, tsubst_flags_t com
complain, ctor);
if (fparms == error_mark_node)
ok = false;
- fargs = tsubst (fargs, tsubst_args, complain, ctor);
if (ci)
ci = tsubst_constraint_info (ci, tsubst_args, complain, ctor);
+ /* Parms are to have DECL_CHAIN tsubsted, which would be skipped if
+ cp_unevaluated_operand. */
+ cp_evaluated ev;
+ fargs = tsubst (fargs, tsubst_args, complain, ctor);
current_template_parms = save_parms;
}
diff --git a/gcc/testsuite/g++.dg/cpp1z/class-deduction71.C
b/gcc/testsuite/g++.dg/cpp1z/class-deduction71.C
new file mode 100644
index 00000000000..2fc71de8d95
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1z/class-deduction71.C
@@ -0,0 +1,6 @@
+// PR c++/93248
+// { dg-do compile { target c++17 } }
+
+template <typename T> struct S
+{ template <typename V> S (T, V, long = 0); };
+using U = decltype(S{0, 4u});
base-commit: 53b28abf8e4ba37e47d3bb05476e0a80ae761567
--
2.18.1
