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c++: Fix invalid pointer-to-member in requires [PR67825]

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A recent change to cmcstl2 led to two tests failing due to this bug: our
valid expression checking in the context of a requires-expression wasn't
catching that an expression of member function type can only appear as the
function operand of a call expression.  Fixed by using convert_to_void to do
the same checking as a discarded-value expression.

This patch also fixes 67825, which already had a testcase, but the testcase
was testing for the wrong behavior.

gcc/cp/ChangeLog
2020-04-04  Jason Merrill  <jason@redhat.com>

	PR c++/67825
	* constraint.cc (tsubst_valid_expression_requirement): Call
	convert_to_void.
This commit is contained in:
Jason Merrill 2020-04-04 11:04:55 -04:00
parent 9f143008c7
commit f1ad7bac76
4 changed files with 33 additions and 2 deletions
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6
gcc/cp/ChangeLog
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@ -1,3 +1,9 @@
2020-04-04 Jason Merrill <jason@redhat.com>
PR c++/67825
* constraint.cc (tsubst_valid_expression_requirement): Call
convert_to_void.
2020-04-04 Jason Merrill <jason@redhat.com>
PR c++/94453

5
gcc/cp/constraint.cc
View File

@ -1864,7 +1864,10 @@ hash_placeholder_constraint (tree c)
static tree
tsubst_valid_expression_requirement (tree t, tree args, subst_info info)
{
return tsubst_expr (t, args, info.complain, info.in_decl, false);
tree r = tsubst_expr (t, args, info.complain, info.in_decl, false);
if (convert_to_void (r, ICV_STATEMENT, info.complain) == error_mark_node)
return error_mark_node;
return r;
}

22
gcc/testsuite/g++.dg/cpp2a/concepts-pmf1.C Normal file
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@ -0,0 +1,22 @@
// Make sure that the requirement fails because a .* expression of function
// type can only be used in a call.
// { dg-do compile { target concepts } }
template<class D, class T>
constexpr decltype(auto) invoke(D (T::*pmd), T&& t)
noexcept(noexcept(t.*pmd))
requires requires { t.*pmd; }
{ return t.*pmd; }
char invoke(...);
struct A
{
int f();
};
int main()
{
static_assert(sizeof(invoke (&A::f, A())) == 1);
}

2
gcc/testsuite/g++.dg/cpp2a/concepts-pr67825.C
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@ -15,6 +15,6 @@ template <class X> concept bool C() {
}
int main() {
static_assert(C<A>());
static_assert(!C<A>());
return 0;
}