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c++: Lambda in friend of constrained class [PR94645]

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In the testcase below, when grokfndecl processes the operator() decl for the
lambda inside the friend function foo, processing_template_decl is rightly 1,
but template_class_depth on the lambda's closure type incorrectly returns 0
instead of 1.

Since processing_template_decl > template_class_depth, this makes grokfndecl
think that the operator() has its own set of template arguments, and so we
attach the innermost set of constraints -- those belonging to struct l -- to the
operator() decl.  We then get confused when checking constraints_satisfied_p on
the operator() because it doesn't have template information and yet has
constraints associated with it.

This patch fixes template_class_depth to return the correct template nesting
level in cases like these, in that when it hits a friend function it walks into
the DECL_FRIEND_CONTEXT of the friend rather than into the CP_DECL_CONTEXT.

gcc/cp/ChangeLog:

	PR c++/94645
	* pt.c (template_class_depth): Walk into the DECL_FRIEND_CONTEXT of a
	friend declaration rather than into its CP_DECL_CONTEXT.

gcc/testsuite/ChangeLog:

	PR c++/94645
	* g++.dg/cpp2a/concepts-lambda6.C: New test.
This commit is contained in:
Patrick Palka 2020-04-23 17:29:55 -04:00
parent b78868459f
commit f9f166251f
4 changed files with 36 additions and 1 deletions
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6
gcc/cp/ChangeLog
View File

@ -1,3 +1,9 @@
2020-04-23 Patrick Palka <ppalka@redhat.com>
PR c++/94645
* pt.c (template_class_depth): Walk into the DECL_FRIEND_CONTEXT of a
friend declaration rather than into its CP_DECL_CONTEXT.
2020-04-23 Iain Sandoe <iain@sandoe.co.uk>
PR c++/94288

7
gcc/cp/pt.c
View File

@ -390,7 +390,12 @@ template_class_depth (tree type)
++depth;
if (DECL_P (type))
type = CP_DECL_CONTEXT (type);
{
if (tree fctx = DECL_FRIEND_CONTEXT (type))
type = fctx;
else
type = CP_DECL_CONTEXT (type);
}
else if (LAMBDA_TYPE_P (type) && LAMBDA_TYPE_EXTRA_SCOPE (type))
type = LAMBDA_TYPE_EXTRA_SCOPE (type);
else

5
gcc/testsuite/ChangeLog
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@ -1,3 +1,8 @@
2020-04-23 Patrick Palka <ppalka@redhat.com>
PR c++/94645
* g++.dg/cpp2a/concepts-lambda6.C: New test.
2019-04-23 Eric Botcazou <ebotcazou@adacore.com>
* g++.dg/opt/store-merging-4.C: New test.

19
gcc/testsuite/g++.dg/cpp2a/concepts-lambda6.C Normal file
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@ -0,0 +1,19 @@
// PR c++/94645
// { dg-do compile { target concepts } }
struct unordered_map {
int cend() const noexcept;
};
template <typename a> concept HasMapInterface = requires(a t) { t.cend(); };
template <typename Mapper> requires HasMapInterface<decltype(Mapper::map())>
struct l {
friend void foo(l opt) { ([]() {})(); }
};
struct p {
static unordered_map map();
};
void g(l<p> *y) { foo(*y); }