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c++: non-standalone surrogate call template

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I noticed we're accidentally prevented from considering a pointer- or
reference-to-function conversion function template if it's not the first
conversion function that's considered, which for the testcase below
results in us accepting the B call but not the A call despite the only
difference between A and B being their order of member declarations.
This patch fixes this so that the outcome of overload resolution doesn't
arbitrarily depend on declaration order here.

gcc/cp/ChangeLog:

	* call.cc (add_template_conv_candidate): Don't check for
	non-empty 'candidates' here.
	(build_op_call): Check it here, before we've considered any
	conversion functions.

gcc/testsuite/ChangeLog:

	* g++.dg/overload/conv-op5.C: New test.
This commit is contained in:
Patrick Palka 2023-07-18 09:22:49 -04:00
parent 1e0f37df1b
commit cde17323f9
2 changed files with 31 additions and 10 deletions
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24
gcc/cp/call.cc
View file

@ -3709,12 +3709,6 @@ add_template_conv_candidate (struct z_candidate **candidates, tree tmpl,
tree return_type, tree access_path,
tree conversion_path, tsubst_flags_t complain)
{
/* Making this work broke PR 71117 and 85118, so until the committee resolves
core issue 2189, let's disable this candidate if there are any call
operators. */
if (*candidates)
return NULL;
return
add_template_candidate_real (candidates, tmpl, NULL_TREE, NULL_TREE,
NULL_TREE, arglist, return_type, access_path,
@ -5290,6 +5284,8 @@ build_op_call (tree obj, vec<tree, va_gc> **args, tsubst_flags_t complain)
LOOKUP_NORMAL, &candidates, complain);
}
bool any_call_ops = candidates != nullptr;
convs = lookup_conversions (type);
for (; convs; convs = TREE_CHAIN (convs))
@ -5306,10 +5302,18 @@ build_op_call (tree obj, vec<tree, va_gc> **args, tsubst_flags_t complain)
continue;
if (TREE_CODE (fn) == TEMPLATE_DECL)
add_template_conv_candidate
(&candidates, fn, obj, *args, totype,
/*access_path=*/NULL_TREE,
/*conversion_path=*/NULL_TREE, complain);
{
/* Making this work broke PR 71117 and 85118, so until the
committee resolves core issue 2189, let's disable this
candidate if there are any call operators. */
if (any_call_ops)
continue;
add_template_conv_candidate
(&candidates, fn, obj, *args, totype,
/*access_path=*/NULL_TREE,
/*conversion_path=*/NULL_TREE, complain);
}
else
add_conv_candidate (&candidates, fn, obj,
*args, /*conversion_path=*/NULL_TREE,

17
gcc/testsuite/g++.dg/overload/conv-op5.C Normal file
View file

@ -0,0 +1,17 @@
// { dg-do compile { target c++11 } }
template<class T> using F = int(*)(T);
using G = int(*)(int*);
struct A {
template<class T> operator F<T>(); // #1
operator G() = delete; // #2
};
struct B {
operator G() = delete; // #2
template<class T> operator F<T>(); // #1
};
int i = A{}(0); // OK, selects #1
int j = B{}(0); // OK, selects #1