re PR c++/84536 (ICE with non-type template parameter)

/cp
2019-02-20  Paolo Carlini  <paolo.carlini@oracle.com>

	PR c++/84536
	* pt.c (tsubst_init): Diagnose an initializer expanding to an
	empty list of expressions; tweak wrt dependent types.
	(regenerate_decl_from_template): For VAR_DECLs call tsubst_init
	instead of tsubst_expr.

/testsuite
2019-02-20  Paolo Carlini  <paolo.carlini@oracle.com>

	PR c++/84536
	* g++.dg/cpp1y/var-templ60.C: New.

From-SVN: r269037

gcc/cp/ChangeLog

+2019-02-20  Paolo Carlini  <paolo.carlini@oracle.com>
+
+	PR c++/84536
+	* pt.c (tsubst_init): Diagnose an initializer expanding to an
+	empty list of expressions; tweak wrt dependent types.
+	(regenerate_decl_from_template): For VAR_DECLs call tsubst_init
+	instead of tsubst_expr.
+
 2019-02-19  Jason Merrill  <jason@redhat.com>
 
 	PR c++/88368 - wrong 'use of deleted function'

gcc/cp/pt.c

@@ -15422,21 +15422,35 @@ tsubst_init (tree init, tree decl, tree args,
 
   init = tsubst_expr (init, args, complain, in_decl, false);
 
-  if (!init && TREE_TYPE (decl) != error_mark_node)
-    {
-      /* If we had an initializer but it
-	 instantiated to nothing,
-	 value-initialize the object.  This will
-	 only occur when the initializer was a
-	 pack expansion where the parameter packs
-	 used in that expansion were of length
-	 zero.  */
-      init = build_value_init (TREE_TYPE (decl),
-			       complain);
-      if (TREE_CODE (init) == AGGR_INIT_EXPR)
-	init = get_target_expr_sfinae (init, complain);
-      if (TREE_CODE (init) == TARGET_EXPR)
-	TARGET_EXPR_DIRECT_INIT_P (init) = true;
+  tree type = TREE_TYPE (decl);
+
+  if (!init && type != error_mark_node)
+    {
+      if (tree auto_node = type_uses_auto (type))
+	{
+	  if (!CLASS_PLACEHOLDER_TEMPLATE (auto_node))
+	    {
+	      if (complain & tf_error)
+		error ("initializer for %q#D expands to an empty list "
+		       "of expressions", decl);
+	      return error_mark_node;
+	    }
+	}
+      else if (!dependent_type_p (type))
+	{
+	  /* If we had an initializer but it
+	     instantiated to nothing,
+	     value-initialize the object.  This will
+	     only occur when the initializer was a
+	     pack expansion where the parameter packs
+	     used in that expansion were of length
+	     zero.  */
+	  init = build_value_init (type, complain);
+	  if (TREE_CODE (init) == AGGR_INIT_EXPR)
+	    init = get_target_expr_sfinae (init, complain);
+	  if (TREE_CODE (init) == TARGET_EXPR)
+	    TARGET_EXPR_DIRECT_INIT_P (init) = true;
+	}
     }
 
   return init;
@@ -24053,9 +24067,8 @@ regenerate_decl_from_template (tree decl, tree tmpl, tree args)
     {
       start_lambda_scope (decl);
       DECL_INITIAL (decl) =
-	tsubst_expr (DECL_INITIAL (code_pattern), args,
-		     tf_error, DECL_TI_TEMPLATE (decl),
-		     /*integral_constant_expression_p=*/false);
+	tsubst_init (DECL_INITIAL (code_pattern), decl, args,
+		     tf_error, DECL_TI_TEMPLATE (decl));
       finish_lambda_scope ();
       if (VAR_HAD_UNKNOWN_BOUND (decl))
 	TREE_TYPE (decl) = tsubst (TREE_TYPE (code_pattern), args,

gcc/testsuite/ChangeLog

+2019-02-20  Paolo Carlini  <paolo.carlini@oracle.com>
+
+	PR c++/84536
+	* g++.dg/cpp1y/var-templ60.C: New.
+
 2019-02-20  Li Jia He  <helijia@linux.ibm.com>
 
 	PR target/88100

gcc/testsuite/g++.dg/cpp1y/var-templ60.C

+// PR c++/84536
+// { dg-do compile { target c++14 } }
+
+template<int... N> auto foo(N...);  // { dg-error "initializer" }
+
+void bar()
+{
+  foo<>();
+}