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P0702R1 - List deduction of vector.

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* pt.c (do_class_deduction): Special-case deduction from a single
	element of related type.

From-SVN: r250584
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Jason Merrill 2017-07-26 13:39:31 -04:00 • committed by Jason Merrill
parent 80e7cb2d6b
commit 6cad8c86b8
3 changed files with 43 additions and 0 deletions
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6
gcc/cp/ChangeLog
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@ -1,3 +1,9 @@
2017-07-26 Jason Merrill <jason@redhat.com>
P0702R1 - List deduction of vector.
* pt.c (do_class_deduction): Special-case deduction from a single
element of related type.
2017-07-26 Leonid Koppel <lkoppel@uwaterloo.ca>
PR c++/67054 - Inherited ctor with non-default-constructible members

18
gcc/cp/pt.c
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@ -25331,6 +25331,24 @@ do_class_deduction (tree ptype, tree tmpl, tree init, int flags,
else if (BRACE_ENCLOSED_INITIALIZER_P (init))
{
try_list_ctor = TYPE_HAS_LIST_CTOR (type);
if (try_list_ctor && CONSTRUCTOR_NELTS (init) == 1)
{
/* As an exception, the first phase in 16.3.1.7 (considering the
initializer list as a single argument) is omitted if the
initializer list consists of a single expression of type cv U,
where U is a specialization of C or a class derived from a
specialization of C. */
tree elt = CONSTRUCTOR_ELT (init, 0)->value;
tree etype = TREE_TYPE (elt);
tree tparms = INNERMOST_TEMPLATE_PARMS (DECL_TEMPLATE_PARMS (tmpl));
tree targs = make_tree_vec (TREE_VEC_LENGTH (tparms));
int err = unify (tparms, targs, type, etype,
UNIFY_ALLOW_DERIVED, /*explain*/false);
if (err == 0)
try_list_ctor = false;
ggc_free (targs);
}
if (try_list_ctor || is_std_init_list (type))
args = make_tree_vector_single (init);
else

19
gcc/testsuite/g++.dg/cpp1z/class-deduction42.C Normal file
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@ -0,0 +1,19 @@
// { dg-options -std=c++1z }
#include <initializer_list>
template <class,class> struct same;
template <class T> struct same<T,T> { };
template <class T>
struct A
{
A(const A&);
A(std::initializer_list<T>);
};
A a { 1 };
A b { a };
same<decltype (a), decltype (b)> s;