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c++: Fix constexpr if and braced functional cast.

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While partially instantiating a generic lambda, we can encounter pack
expansions or constexpr if where we can't actually do the substitution
immediately, and instead remember a partial instantiation context
in *_EXTRA_ARGS.  This includes any local_specializations used in the
pattern or condition.  In this testcase our tree walk wasn't finding the use
of i because we weren't walking into the type of a CONSTRUCTOR.  Fixed by
moving the code for doing that from find_parameter_packs_r into
cp_walk_subtrees.

2020-02-11  Jason Merrill  <jason@redhat.com>

	PR c++/92583
	PR c++/92654
	* tree.c (cp_walk_subtrees): Walk CONSTRUCTOR types here.
	* pt.c (find_parameter_packs_r): Not here.
This commit is contained in:
Jason Merrill 2020-02-10 14:12:07 +01:00
parent 68bb7e3b9d
commit c2368db567
5 changed files with 37 additions and 4 deletions
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7
gcc/cp/ChangeLog
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@ -1,3 +1,10 @@
2020-02-12 Jason Merrill <jason@redhat.com>
PR c++/92583
PR c++/92654
* tree.c (cp_walk_subtrees): Walk CONSTRUCTOR types here.
* pt.c (find_parameter_packs_r): Not here.
2020-02-12 Iain Sandoe <iain@sandoe.co.uk>
* coroutines.cc (build_actor_fn): Implement deallocation function

3
gcc/cp/pt.c
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@ -3924,9 +3924,6 @@ find_parameter_packs_r (tree *tp, int *walk_subtrees, void* data)
case TEMPLATE_DECL:
if (!DECL_TEMPLATE_TEMPLATE_PARM_P (t))
return NULL_TREE;
gcc_fallthrough();
case CONSTRUCTOR:
cp_walk_tree (&TREE_TYPE (t),
&find_parameter_packs_r, ppd, ppd->visited);
return NULL_TREE;

5
gcc/cp/tree.c
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@ -5024,6 +5024,11 @@ cp_walk_subtrees (tree *tp, int *walk_subtrees_p, walk_tree_fn func,
*walk_subtrees_p = 0;
break;
case CONSTRUCTOR:
if (COMPOUND_LITERAL_P (*tp))
WALK_SUBTREE (TREE_TYPE (*tp));
break;
case TRAIT_EXPR:
WALK_SUBTREE (TRAIT_EXPR_TYPE1 (*tp));
WALK_SUBTREE (TRAIT_EXPR_TYPE2 (*tp));

2
gcc/testsuite/g++.dg/cpp0x/nondeduced7.C
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@ -2,5 +2,5 @@
// { dg-do compile { target c++11 } }
template<typename, int> struct A;
template<typename T> struct A<T, T{}> {}; // { dg-error "partial specialization" }
template<typename T> struct A<T, T{}> {}; // { dg-error "partial specialization|involves template parameter" }
A<int, 0> a;

24
gcc/testsuite/g++.dg/cpp1z/constexpr-if-lambda3.C Normal file
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@ -0,0 +1,24 @@
// PR c++/92583
// { dg-do compile { target c++17 } }
template <int> struct a {
constexpr operator int() { return 42; }
};
template <typename> using b = int;
template <typename d, d> struct e {};
template <typename d, d g> using h = e<d, __integer_pack(g)...>;
template <typename j, typename k, k... index> void apply(j f, e<k, index...>) {
(f(a<index>{}), ...);
}
template <auto l, typename j> void m(j f) {
using k = b<decltype(l)>;
using n = h<k, l>;
apply(f, n{});
}
template <int, int c> void o() {
auto p = [](auto i) {
if constexpr (a<i>{}) ;
};
m<c>(p);
}
auto q() { o<0, 1>; }