[gcc r11-9081] c++: constrained variable template issues [PR98486]

[gcc r11-9081] c++: constrained variable template issues [PR98486]

[Patrick Palka]

https://gcc.gnu.org/g:729cf2ea979f396e706625b1669087d5920b8c2a

commit r11-9081-g729cf2ea979f396e706625b1669087d5920b8c2a
Author: Patrick Palka <ppalka@redhat.com>
Date:   Thu Sep 16 15:03:55 2021 -0400

    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:
---
 gcc/cp/constraint.cc                              |  8 +++++---
 gcc/cp/decl.c                                     | 11 +++++++++++
 gcc/cp/pt.c                                       |  3 ++-
 gcc/testsuite/g++.dg/cpp2a/concepts-var-templ1.C  |  9 +++++++++
 gcc/testsuite/g++.dg/cpp2a/concepts-var-templ1a.C | 14 ++++++++++++++
 gcc/testsuite/g++.dg/cpp2a/concepts-var-templ1b.C | 15 +++++++++++++++
 6 files changed, 56 insertions(+), 4 deletions(-)

diff --git a/gcc/cp/constraint.cc b/gcc/cp/constraint.cc
index 4af7018f1a5..76802964c70 100644
--- 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 f21db4d560d..a3c06fdae8e 100644
--- 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 46ad819239e..31bd51b7c9d 100644
--- 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
index 00000000000..80b48ba3a3d
--- /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
index 00000000000..b12d37d8b7e
--- /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
index 00000000000..37d7f0fc654
--- /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" }