PR c++/92576 - redeclaration of variable template.

The variable templates patch way back when forgot to add handling here.  The
simplest answer seems to be recursing to the underlying declaration.

	* decl.c (redeclaration_error_message): Recurse for variable
	templates.

From-SVN: r279472

gcc/cp/ChangeLog

 2019-12-17  Jason Merrill  <jason@redhat.com>
 
+	PR c++/92576 - redeclaration of variable template.
+	* decl.c (redeclaration_error_message): Recurse for variable
+	templates.
+
+2019-12-17  Jason Merrill  <jason@redhat.com>
+
 	* name-lookup.c (get_std_name_hint): Add std::byte.
 
 2019-12-17  Jakub Jelinek  <jakub@redhat.com>

gcc/cp/decl.c

@@ -2977,20 +2977,14 @@ redeclaration_error_message (tree newdecl, tree olddecl)
     {
       tree nt, ot;
 
-      if (TREE_CODE (DECL_TEMPLATE_RESULT (newdecl)) == TYPE_DECL)
-	{
-	  if (COMPLETE_TYPE_P (TREE_TYPE (newdecl))
-	      && COMPLETE_TYPE_P (TREE_TYPE (olddecl)))
-	    return G_("redefinition of %q#D");
-	  return NULL;
-	}
-
       if (TREE_CODE (DECL_TEMPLATE_RESULT (newdecl)) == CONCEPT_DECL)
         return G_("redefinition of %q#D");
 
-      if (TREE_CODE (DECL_TEMPLATE_RESULT (newdecl)) != FUNCTION_DECL
-	  || (DECL_TEMPLATE_RESULT (newdecl)
-	      == DECL_TEMPLATE_RESULT (olddecl)))
+      if (TREE_CODE (DECL_TEMPLATE_RESULT (newdecl)) != FUNCTION_DECL)
+	return redeclaration_error_message (DECL_TEMPLATE_RESULT (newdecl),
+					    DECL_TEMPLATE_RESULT (olddecl));
+
+      if (DECL_TEMPLATE_RESULT (newdecl) == DECL_TEMPLATE_RESULT (olddecl))
 	return NULL;
 
       nt = DECL_TEMPLATE_RESULT (newdecl);

gcc/testsuite/g++.dg/cpp1y/var-templ32.C

@@ -4,4 +4,4 @@ template<typename T>
 bool V1 = true;
 
 template<typename T>
-bool V1<int> = false; // { dg-error "primary template|not deducible" }
+bool V1<int> = false; // { dg-error "primary template|redefinition|not deducible" }

gcc/testsuite/g++.dg/cpp1y/var-templ65.C

+// PR c++/84255
+// { dg-do compile { target c++14 } }
+
+template<typename T> constexpr int var;
+template<typename T> constexpr int var = 1; // { dg-error "redefinition" }