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c++: abbreviated function template friend matching [PR96106] 

In the below testcase, duplicate_decls wasn't merging the tsubsted
friend declaration for 'void add(auto)' with its definition, because
reduce_template_parm_level (during tsubst_friend_function) lost the
DECL_VIRTUAL_P flag on the auto's invented template parameter, which
caused template_heads_equivalent_p to deem the two template heads as not
equivalent in C++20 mode.

This patch makes reduce_template_parm_level carry over the
DECL_VIRTUAL_P flag from the original TEMPLATE_PARM_DECL.

gcc/cp/ChangeLog:

	PR c++/96106
	* pt.c (reduce_template_parm_level): Propagate DECL_VIRTUAL_P
	from the original TEMPLATE_PARM_DECL to the new lowered one.

gcc/testsuite/ChangeLog:

	PR c++/96106
	* g++.dg/concepts/abbrev7.C: New test.
This commit is contained in:
Patrick Palka 2020-07-29 22:06:36 -04:00
parent dc3d1e1814
commit f31dd9beb9
2 changed files with 15 additions and 0 deletions
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1
gcc/cp/pt.c
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@ -4453,6 +4453,7 @@ reduce_template_parm_level (tree index, tree type, int levels, tree args,
type);
TREE_CONSTANT (decl) = TREE_CONSTANT (orig_decl);
TREE_READONLY (decl) = TREE_READONLY (orig_decl);
DECL_VIRTUAL_P (decl) = DECL_VIRTUAL_P (orig_decl);
DECL_ARTIFICIAL (decl) = 1;
SET_DECL_TEMPLATE_PARM_P (decl);

14
gcc/testsuite/g++.dg/concepts/abbrev7.C Normal file
View File

@ -0,0 +1,14 @@
// PR c++/96106
// { dg-do compile { target concepts } }
template<typename>
struct number {
friend void add(auto);
};
void add(auto) { }
void foo() {
number<int> n;
add(n); // { dg-bogus "ambiguous" }
}