During CTAD, we currently perform the first phase of overload resolution from [over.match.list] only if the class template has a list constructor. But according to [over.match.class.deduct]/4 it should be enough to just have a guide that looks like a list constructor (which is a more general criterion in light of user-defined guides).
Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for trunk? PR c++/106366 gcc/cp/ChangeLog: * pt.cc (do_class_deduction): Don't consider TYPE_HAS_LIST_CTOR when setting try_list_ctor. Reset args even when try_list_ctor is true and there are no list candidates. Call resolve_args on the reset args. gcc/testsuite/ChangeLog: * g++.dg/cpp1z/class-deduction112.C: New test. --- gcc/cp/pt.cc | 25 +++++++++---------- .../g++.dg/cpp1z/class-deduction112.C | 14 +++++++++++ 2 files changed, 26 insertions(+), 13 deletions(-) create mode 100644 gcc/testsuite/g++.dg/cpp1z/class-deduction112.C diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc index 718dfa5bfa8..0f26d6f5bce 100644 --- a/gcc/cp/pt.cc +++ b/gcc/cp/pt.cc @@ -30250,8 +30250,8 @@ do_class_deduction (tree ptype, tree tmpl, tree init, else if (BRACE_ENCLOSED_INITIALIZER_P (init)) { list_init_p = true; - try_list_ctor = TYPE_HAS_LIST_CTOR (type); - if (try_list_ctor && CONSTRUCTOR_NELTS (init) == 1 + try_list_ctor = true; + if (CONSTRUCTOR_NELTS (init) == 1 && !CONSTRUCTOR_IS_DESIGNATED_INIT (init)) { /* As an exception, the first phase in 16.3.1.7 (considering the @@ -30310,26 +30310,25 @@ do_class_deduction (tree ptype, tree tmpl, tree init, tree fndecl = error_mark_node; - /* If this is list-initialization and the class has a list constructor, first + /* If this is list-initialization and the class has a list guide, first try deducing from the list as a single argument, as [over.match.list]. */ - tree list_cands = NULL_TREE; - if (try_list_ctor && cands) - for (lkp_iterator iter (cands); iter; ++iter) - { - tree dg = *iter; + if (try_list_ctor) + { + tree list_cands = NULL_TREE; + for (tree dg : lkp_range (cands)) if (is_list_ctor (dg)) list_cands = lookup_add (dg, list_cands); - } - if (list_cands) - { - fndecl = perform_dguide_overload_resolution (list_cands, args, tf_none); - + if (list_cands) + fndecl = perform_dguide_overload_resolution (list_cands, args, tf_none); if (fndecl == error_mark_node) { /* That didn't work, now try treating the list as a sequence of arguments. */ release_tree_vector (args); args = make_tree_vector_from_ctor (init); + args = resolve_args (args, complain); + if (args == NULL) + return error_mark_node; } } diff --git a/gcc/testsuite/g++.dg/cpp1z/class-deduction112.C b/gcc/testsuite/g++.dg/cpp1z/class-deduction112.C new file mode 100644 index 00000000000..8da5868ff98 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp1z/class-deduction112.C @@ -0,0 +1,14 @@ +// PR c++/106366 +// { dg-do compile { target c++17 } } + +#include <initializer_list> + +template<class T> +struct A { A(...); }; + +template<typename T> +A(std::initializer_list<T>) -> A<T>; + +A a{1,2,3}; +using type = decltype(a); +using type = A<int>; -- 2.37.1.208.ge72d93e88c