[gcc r13-2775] c++ modules: partial variable template specializations [PR106826]

[gcc r13-2775] c++ modules: partial variable template specializations [PR106826]

[Patrick Palka]

https://gcc.gnu.org/g:32d8123cd6ce87acb557aec230e8359051316f9f

commit r13-2775-g32d8123cd6ce87acb557aec230e8359051316f9f
Author: Patrick Palka <ppalka@redhat.com>
Date:   Thu Sep 22 08:46:23 2022 -0400

    c++ modules: partial variable template specializations [PR106826]
    
    With partial variable template specializations, it looks like we
    stream the VAR_DECL (i.e. the DECL_TEMPLATE_RESULT of the corresponding
    TEMPLATE_DECL) since process_partial_specialization adds it to the
    specializations table, but we end up never streaming the corresponding
    TEMPLATE_DECL itself that's reachable only from the primary template's
    DECL_TEMPLATE_SPECIALIZATIONS list, which leads to this list being
    incomplete on stream-in.
    
    The modules machinery already has special logic for streaming partial
    specializations of class templates; this patch attempts to generalize
    it to handle those of variable templates as well.
    
            PR c++/106826
    
    gcc/cp/ChangeLog:
    
            * module.cc (trees_out::decl_value): Use get_template_info in
            the MK_partial case to handle both VAR_DECL and TYPE_DECL.
            (trees_out::key_mergeable): Likewise.
            (trees_in::key_mergeable): Likewise.
            (has_definition): Consider DECL_INITIAL of a partial variable
            template specialization.
            (depset::hash::make_dependency): Handle partial variable template
            specializations too.
    
    gcc/testsuite/ChangeLog:
    
            * g++.dg/modules/partial-2_a.C: New test.
            * g++.dg/modules/partial-2_b.C: New test.

Diff:
---
 gcc/cp/module.cc                           | 32 ++++++++++++----------
 gcc/testsuite/g++.dg/modules/partial-2_a.C | 43 ++++++++++++++++++++++++++++++
 gcc/testsuite/g++.dg/modules/partial-2_b.C | 21 +++++++++++++++
 3 files changed, 82 insertions(+), 14 deletions(-)

diff --git a/gcc/cp/module.cc b/gcc/cp/module.cc
index 9a9ef4e3332..f23832cb56a 100644
--- a/gcc/cp/module.cc
+++ b/gcc/cp/module.cc
@@ -7789,8 +7789,9 @@ trees_out::decl_value (tree decl, depset *dep)
 	    }
 	  else
 	    {
-	      tree_node (CLASSTYPE_TI_TEMPLATE (TREE_TYPE (inner)));
-	      tree_node (CLASSTYPE_TI_ARGS (TREE_TYPE (inner)));
+	      tree ti = get_template_info (inner);
+	      tree_node (TI_TEMPLATE (ti));
+	      tree_node (TI_ARGS (ti));
 	    }
 	}
       tree_node (get_constraints (decl));
@@ -10625,9 +10626,10 @@ trees_out::key_mergeable (int tag, merge_kind mk, tree decl, tree inner,
 
 	case MK_partial:
 	  {
+	    tree ti = get_template_info (inner);
 	    key.constraints = get_constraints (inner);
-	    key.ret = CLASSTYPE_TI_TEMPLATE (TREE_TYPE (inner));
-	    key.args = CLASSTYPE_TI_ARGS (TREE_TYPE (inner));
+	    key.ret = TI_TEMPLATE (ti);
+	    key.args = TI_ARGS (ti);
 	  }
 	  break;
 	}
@@ -10866,8 +10868,8 @@ trees_in::key_mergeable (int tag, merge_kind mk, tree decl, tree inner,
 	       spec; spec = TREE_CHAIN (spec))
 	    {
 	      tree tmpl = TREE_VALUE (spec);
-	      if (template_args_equal (key.args,
-				       CLASSTYPE_TI_ARGS (TREE_TYPE (tmpl)))
+	      tree ti = get_template_info (tmpl);
+	      if (template_args_equal (key.args, TI_ARGS (ti))
 		  && cp_tree_equal (key.constraints,
 				    get_constraints
 				    (DECL_TEMPLATE_RESULT (tmpl))))
@@ -11381,8 +11383,7 @@ has_definition (tree decl)
 
     case VAR_DECL:
       if (DECL_LANG_SPECIFIC (decl)
-	  && DECL_TEMPLATE_INFO (decl)
-	  && DECL_USE_TEMPLATE (decl) < 2)
+	  && DECL_TEMPLATE_INFO (decl))
 	return DECL_INITIAL (decl);
       else
 	{
@@ -12498,11 +12499,14 @@ depset::hash::make_dependency (tree decl, entity_kind ek)
 
   if (!dep)
     {
-      if (DECL_IMPLICIT_TYPEDEF_P (decl)
-	  /* ... not an enum, for instance.  */
-	  && RECORD_OR_UNION_TYPE_P (TREE_TYPE (decl))
-	  && TYPE_LANG_SPECIFIC (TREE_TYPE (decl))
-	  && CLASSTYPE_USE_TEMPLATE (TREE_TYPE (decl)) == 2)
+      if ((DECL_IMPLICIT_TYPEDEF_P (decl)
+	   /* ... not an enum, for instance.  */
+	   && RECORD_OR_UNION_TYPE_P (TREE_TYPE (decl))
+	   && TYPE_LANG_SPECIFIC (TREE_TYPE (decl))
+	   && CLASSTYPE_USE_TEMPLATE (TREE_TYPE (decl)) == 2)
+	  || (VAR_P (decl)
+	      && DECL_LANG_SPECIFIC (decl)
+	      && DECL_USE_TEMPLATE (decl) == 2))
 	{
 	  /* A partial or explicit specialization. Partial
 	     specializations might not be in the hash table, because
@@ -12515,7 +12519,7 @@ depset::hash::make_dependency (tree decl, entity_kind ek)
 	     dep_hash, and then convert the dep we just found into a
 	     redirect.  */
 
-	  tree ti = TYPE_TEMPLATE_INFO (TREE_TYPE (decl));
+	  tree ti = get_template_info (decl);
 	  tree tmpl = TI_TEMPLATE (ti);
 	  tree partial = NULL_TREE;
 	  for (tree spec = DECL_TEMPLATE_SPECIALIZATIONS (tmpl);
diff --git a/gcc/testsuite/g++.dg/modules/partial-2_a.C b/gcc/testsuite/g++.dg/modules/partial-2_a.C
new file mode 100644
index 00000000000..2681bb59ce8
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/partial-2_a.C
@@ -0,0 +1,43 @@
+// PR c++/106826
+// { dg-additional-options -fmodules-ts }
+// { dg-module-cmi pr106826 }
+export module pr106826;
+
+template<class T> constexpr bool is_reference_v = false;
+template<class T> constexpr bool is_reference_v<T&> = true;
+template<class T> constexpr bool is_reference_v<T&&> = true;
+
+struct A {
+  template<class T> static constexpr bool is_reference_v = false;
+};
+
+template<class T> constexpr bool A::is_reference_v<T&> = true;
+template<class T> constexpr bool A::is_reference_v<T&&> = true;
+
+#if __cpp_concepts
+namespace concepts {
+  template<class T> bool is_reference_v;
+
+  template<class T> requires __is_same(T, T&)
+  constexpr bool is_reference_v<T> = true;
+
+  template<class T> requires __is_same(T, T&&) && (!__is_same(T, T&))
+  constexpr bool is_reference_v<T> = true;
+
+  template<class T> requires (!__is_same(T, T&)) && (!__is_same(T, T&&))
+  constexpr bool is_reference_v<T> = false;
+
+  struct A {
+    template<class T> static bool is_reference_v;
+  };
+
+  template<class T> requires __is_same(T, T&)
+  constexpr bool A::is_reference_v<T> = true;
+
+  template<class T> requires __is_same(T, T&&) && (!__is_same(T, T&))
+  constexpr bool A::is_reference_v<T> = true;
+
+  template<class T> requires (!__is_same(T, T&)) && (!__is_same(T, T&&))
+  constexpr bool A::is_reference_v<T> = false;
+}
+#endif
diff --git a/gcc/testsuite/g++.dg/modules/partial-2_b.C b/gcc/testsuite/g++.dg/modules/partial-2_b.C
new file mode 100644
index 00000000000..0af41ef5e5e
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/partial-2_b.C
@@ -0,0 +1,21 @@
+// PR c++/106826
+// { dg-additional-options -fmodules-ts }
+module pr106826;
+
+static_assert(is_reference_v<int&>);
+static_assert(is_reference_v<int&&>);
+static_assert(!is_reference_v<int>);
+
+static_assert(A::is_reference_v<long&>);
+static_assert(A::is_reference_v<long&&>);
+static_assert(!A::is_reference_v<long>);
+
+#if __cpp_concepts
+static_assert(concepts::is_reference_v<char&>);
+static_assert(concepts::is_reference_v<char&&>);
+static_assert(!concepts::is_reference_v<char>);
+
+static_assert(concepts::A::is_reference_v<bool&>);
+static_assert(concepts::A::is_reference_v<bool&&>);
+static_assert(!concepts::A::is_reference_v<bool>);
+#endif