c++: explicit inst w/ similar constrained partial specs [PR104634]

Here we neglect to emit the definitions of A<double>::f2 and A<double*>::f4
despite the explicit instantiations ultimately because TREE_PUBLIC isn't
set on the corresponding partial specializations, whose declarations are
created from maybe_new_partial_specialization which is responsible for
disambiguating them from the first and third partial specializations (which
have the same class-head but different constraints).  This makes grokfndecl
in turn clear TREE_PUBLIC for f2 and f4 as if they have internal linkage.

This patch fixes this by setting TREE_PUBLIC appropriately for such partial
specializations.

	PR c++/104634

gcc/cp/ChangeLog:

	* pt.cc (maybe_new_partial_specialization): Propagate TREE_PUBLIC
	to the newly created partial specialization.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp2a/concepts-explicit-inst6.C: New test.

Reviewed-by: Jason Merrill <jason@redhat.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 6900d17..8d050e8 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -980,6 +980,7 @@ maybe_new_partial_specialization (tree& type)
       DECL_SOURCE_LOCATION (d) = input_location;
       TREE_PRIVATE (d) = (current_access_specifier == access_private_node);
       TREE_PROTECTED (d) = (current_access_specifier == access_protected_node);
+      TREE_PUBLIC (d) = TREE_PUBLIC (DECL_TEMPLATE_RESULT (tmpl));
 
       set_instantiating_module (d);
       DECL_MODULE_EXPORT_P (d) = DECL_MODULE_EXPORT_P (tmpl);