We were attempting to issue a -Wctad-maybe-unsupported warning even when
complain=tf_none, which led to a crash in the first testcase below and a
bogus error during overload resolution in the second testcase.
PR c++/105143
gcc/cp/ChangeLog:
* pt.cc (do_class_deduction): Check complain before attempting
to issue a -Wctad-maybe-unsupported warning.
gcc/testsuite/ChangeLog:
* g++.dg/cpp2a/nodiscard1.C: New test.
* g++.dg/warn/Wctad-maybe-unsupported4.C: New test.
/* If CTAD succeeded but the type doesn't have any explicit deduction
guides, this deduction might not be what the user intended. */
- if (fndecl != error_mark_node && !any_dguides_p)
+ if (fndecl != error_mark_node && !any_dguides_p && (complain & tf_warning))
{
if ((!DECL_IN_SYSTEM_HEADER (fndecl)
|| global_dc->dc_warn_system_headers)
--- /dev/null
+// PR c++/105143
+// { dg-do compile { target c++20 } }
+// We used to crash here with "Error reporting routines re-entered".
+
+template<class...> struct A { };
+
+template<A V> using type = int;
+
+template<A V> [[nodiscard]] type<V> get();
+
+int main() {
+ get<{}>(); // { dg-warning "nodiscard" }
+}
--- /dev/null
+// PR c++/105143
+// { dg-do compile { target c++17 } }
+// { dg-additional-options "-Werror=ctad-maybe-unsupported" }
+
+template<class...> struct A { };
+
+template<template<class...> class TT> auto f(...) -> decltype(TT()); // #1
+template<template<class...> class TT> void f(int); // #2
+
+int main() {
+ f<A>(0); // Calls #2 without issuing a -Wctad-maybe-unsupported
+ // diagnostic for #1.
+}