c++: constrained variable template issues [PR98486]

This fixes some issues with constrained variable templates:

  - Constraints aren't checked when explicitly specializing a variable
    template.
  - Constraints aren't attached to a static data member template at
    parse time.
  - Constraints don't get propagated when (partially) instantiating a
    static data member template, so we need to make sure to look up
    constraints using the most general template during satisfaction.

	PR c++/98486

gcc/cp/ChangeLog:

	* constraint.cc (get_normalized_constraints_from_decl): Always
	look up constraints using the most general template.
	* decl.c (grokdeclarator): Set constraints on a static data
	member template.
	* pt.c (determine_specialization): Check constraints on a
	variable template.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp2a/concepts-var-templ1.C: New test.
	* g++.dg/cpp2a/concepts-var-templ1a.C: New test.
	* g++.dg/cpp2a/concepts-var-templ1b.C: New test.

(cherry picked from commit 2e2e65a46d2674bed53afd211493876ee2b79453)

diff --git a/gcc/cp/constraint.cc b/gcc/cp/constraint.cc
index 4af7018f1a57e167c7f956ac70f1499f1ba45bcb..76802964c701cd325dbc4e6a591722fcea8f34a4 100644 (file)
--- a/gcc/cp/constraint.cc
+++ b/gcc/cp/constraint.cc
@@ -933,13 +933,15 @@ get_normalized_constraints_from_decl (tree d, bool diag = false)
       tmpl = most_general_template (tmpl);
   }
 
+  d = tmpl ? tmpl : decl;
+
   /* If we're not diagnosing errors, use cached constraints, if any.  */
   if (!diag)
-    if (tree *p = hash_map_safe_get (normalized_map, tmpl))
+    if (tree *p = hash_map_safe_get (normalized_map, d))
       return *p;
 
   tree norm = NULL_TREE;
-  if (tree ci = get_constraints (decl))
+  if (tree ci = get_constraints (d))
     {
       push_nested_class_guard pncs (DECL_CONTEXT (d));
 
@@ -951,7 +953,7 @@ get_normalized_constraints_from_decl (tree d, bool diag = false)
     }
 
   if (!diag)
-    hash_map_safe_put<hm_ggc> (normalized_map, tmpl, norm);
+    hash_map_safe_put<hm_ggc> (normalized_map, d, norm);
 
   return norm;
 }

diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
index f21db4d560dba857b73a35591a22f6a86972aae2..a3c06fdae8e70597043a4f59c4898c4551e544e7 100644 (file)
--- a/gcc/cp/decl.c
+++ b/gcc/cp/decl.c
@@ -13831,6 +13831,17 @@ grokdeclarator (const cp_declarator *declarator,
                    if (declspecs->gnu_thread_keyword_p)
                      SET_DECL_GNU_TLS_P (decl);
                  }
+
+               /* Set the constraints on the declaration.  */
+               bool memtmpl = (processing_template_decl
+                               > template_class_depth (current_class_type));
+               if (memtmpl)
+                 {
+                   tree tmpl_reqs
+                     = TEMPLATE_PARMS_CONSTRAINTS (current_template_parms);
+                   tree ci = build_constraints (tmpl_reqs, NULL_TREE);
+                   set_constraints (decl, ci);
+                 }
              }
            else
              {

diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 46ad819239ed204e47cfd469440dc14fdfc117f2..31bd51b7c9df148bcc193b1b00b1c44b67668fda 100644 (file)
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -2207,7 +2207,8 @@ determine_specialization (tree template_id,
       targs = coerce_template_parms (parms, explicit_targs, fns,
                                     tf_warning_or_error,
                                     /*req_all*/true, /*use_defarg*/true);
-      if (targs != error_mark_node)
+      if (targs != error_mark_node
+         && constraints_satisfied_p (fns, targs))
         templates = tree_cons (targs, fns, templates);
     }
   else for (lkp_iterator iter (fns); iter; ++iter)

diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-var-templ1.C b/gcc/testsuite/g++.dg/cpp2a/concepts-var-templ1.C
new file mode 100644 (file)
index 0000000..80b48ba
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-var-templ1.C
@@ -0,0 +1,9 @@
+// PR c++/98486
+// { dg-do compile { target c++20 } }
+
+template<class T, class U> concept C = __is_same(T, U);
+
+template<C<int>> int v;
+
+template<> int v<int>;
+template<> int v<char>; // { dg-error "match" }

diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-var-templ1a.C b/gcc/testsuite/g++.dg/cpp2a/concepts-var-templ1a.C
new file mode 100644 (file)
index 0000000..b12d37d
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-var-templ1a.C
@@ -0,0 +1,14 @@
+// PR c++/98486
+// { dg-do compile { target c++20 } }
+
+template<class T, class U> concept C = __is_same(T, U);
+
+struct A {
+  template<C<int>> static int v;
+};
+
+template<> int A::v<int>;
+template<> int A::v<char>; // { dg-error "match" }
+
+int x = A::v<int>;
+int y = A::v<char>; // { dg-error "invalid" }

diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-var-templ1b.C b/gcc/testsuite/g++.dg/cpp2a/concepts-var-templ1b.C
new file mode 100644 (file)
index 0000000..37d7f0f
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-var-templ1b.C
@@ -0,0 +1,15 @@
+// PR c++/98486
+// { dg-do compile { target c++20 } }
+
+template<class T, class U> concept C = __is_same(T, U);
+
+template<class T>
+struct A {
+  template<C<T>> static int v;
+};
+
+template<> template<> int A<int>::v<int>;
+template<> template<> int A<int>::v<char>; // { dg-error "match" }
+
+int x = A<int>::v<int>;
+int y = A<int>::v<char>; // { dg-error "invalid" }