Bootstrapped and regtested on x86_64-pc-linux-gnu, OK for trunk?

-- >8 --

There are two separate issues making various template parameters behave
as if they were TU-local.

Firstly, the TU-local detection code uses WILDCARD_TYPE_P to check for
types that are not yet concrete; for some reason UNBOUND_CLASS_TEMPLATE
is not on that list.  I don't see any particular reason why it shouldn't
be, so this patch adds it; this may solve other latent issues as well.

Secondly, the TEMPLATE_DECL for a type with expressions involving
template template parameters is currently always constrained to internal
linkage, because the result does not have TREE_PUBLIC set.  Rather than
messing with TREE_PUBLIC here, I think rather we just should ensure that
we only attempt to constrain visiblity of templates of type, variable,
or function decls.

        PR c++/118846

gcc/cp/ChangeLog:

        * cp-tree.h (WILDCARD_TYPE_P): Include UNBOUND_CLASS_TEMPLATE.
        * decl2.cc (min_vis_expr_r): Don't rely on TREE_PUBLIC always
        being accurate for the DECL_TEMPLATE_RESULT of a template.

gcc/testsuite/ChangeLog:

        * g++.dg/modules/pr118846_a.C: New test.
        * g++.dg/modules/pr118846_b.C: New test.

Signed-off-by: Nathaniel Shead <nathanielosh...@gmail.com>
---
 gcc/cp/cp-tree.h                          |  1 +
 gcc/cp/decl2.cc                           | 22 ++++++++++++++--------
 gcc/testsuite/g++.dg/modules/pr118846_a.C | 18 ++++++++++++++++++
 gcc/testsuite/g++.dg/modules/pr118846_b.C | 10 ++++++++++
 4 files changed, 43 insertions(+), 8 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/modules/pr118846_a.C
 create mode 100644 gcc/testsuite/g++.dg/modules/pr118846_b.C

diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index ec976928f5f..3d0349f66a3 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -2325,6 +2325,7 @@ enum languages { lang_c, lang_cplusplus };
    || TREE_CODE (T) == TYPENAME_TYPE                   \
    || TREE_CODE (T) == TYPEOF_TYPE                     \
    || TREE_CODE (T) == BOUND_TEMPLATE_TEMPLATE_PARM    \
+   || TREE_CODE (T) == UNBOUND_CLASS_TEMPLATE          \
    || TREE_CODE (T) == DECLTYPE_TYPE                   \
    || TREE_CODE (T) == TRAIT_TYPE                      \
    || TREE_CODE (T) == DEPENDENT_OPERATOR_TYPE         \
diff --git a/gcc/cp/decl2.cc b/gcc/cp/decl2.cc
index 593dcaa4e2d..4415cea93e0 100644
--- a/gcc/cp/decl2.cc
+++ b/gcc/cp/decl2.cc
@@ -2786,6 +2786,19 @@ min_vis_expr_r (tree *tp, int */*walk_subtrees*/, void 
*data)
   tree t = *tp;
   if (TREE_CODE (t) == PTRMEM_CST)
     t = PTRMEM_CST_MEMBER (t);
+
+  if (TREE_CODE (t) == TEMPLATE_DECL)
+    {
+      if (DECL_ALIAS_TEMPLATE_P (t) || concept_definition_p (t))
+       /* FIXME: We don't maintain TREE_PUBLIC / DECL_VISIBILITY for
+          alias templates so we can't trust it here (PR107906).  Ditto
+          for concepts.  */
+       return NULL_TREE;
+      t = DECL_TEMPLATE_RESULT (t);
+      if (!t)
+       return NULL_TREE;
+    }
+
   switch (TREE_CODE (t))
     {
     case CAST_EXPR:
@@ -2797,17 +2810,10 @@ min_vis_expr_r (tree *tp, int */*walk_subtrees*/, void 
*data)
     case NEW_EXPR:
     case CONSTRUCTOR:
     case LAMBDA_EXPR:
+    case TYPE_DECL:
       tpvis = type_visibility (TREE_TYPE (t));
       break;
 
-    case TEMPLATE_DECL:
-      if (DECL_ALIAS_TEMPLATE_P (t) || concept_definition_p (t))
-       /* FIXME: We don't maintain TREE_PUBLIC / DECL_VISIBILITY for
-          alias templates so we can't trust it here (PR107906).  Ditto
-          for concepts.  */
-       break;
-      t = DECL_TEMPLATE_RESULT (t);
-      /* Fall through.  */
     case VAR_DECL:
     case FUNCTION_DECL:
       if (decl_constant_var_p (t))
diff --git a/gcc/testsuite/g++.dg/modules/pr118846_a.C 
b/gcc/testsuite/g++.dg/modules/pr118846_a.C
new file mode 100644
index 00000000000..bbbdde78457
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/pr118846_a.C
@@ -0,0 +1,18 @@
+// PR c++/118846
+// { dg-additional-options "-fmodules" }
+// { dg-module-cmi M }
+
+export module M;
+
+template <int N> struct integral_constant { static constexpr int value = N; };
+template <template <class> class> constexpr int cx_count_if() { return 0; }
+template <template <class> class P> struct mp_count_if_impl {
+  using type = integral_constant<cx_count_if<P>()>;
+};
+
+template <template <class> class> struct consume {
+  static constexpr bool value = true;
+};
+template <class P> struct use {
+  using type = consume<P::template fn>;
+};
diff --git a/gcc/testsuite/g++.dg/modules/pr118846_b.C 
b/gcc/testsuite/g++.dg/modules/pr118846_b.C
new file mode 100644
index 00000000000..a2f28894630
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/pr118846_b.C
@@ -0,0 +1,10 @@
+// PR c++/118846
+// { dg-additional-options "-fmodules" }
+
+module M;
+
+template <typename> struct S {
+  template <typename> struct fn {};
+};
+static_assert(mp_count_if_impl<S>::type::value == 0);
+static_assert(use<S<int>>::type::value);
-- 
2.47.0

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