Re: [C++ Patch/RFC] PR 60389

[Paolo Carlini]

Hi,

On 03/07/2014 06:36 PM, Jason Merrill wrote:

Inherited constructors inherit 'constexpr' from the designated base; B::B isn't constexpr because A::A isn't, and we should say that at the beginning of is_valid_constexpr_fn.

Ok, then something like the below? (passes testing)

Thanks,
Paolo.

///////////////////////

Index: cp/semantics.c
===================================================================
--- cp/semantics.c      (revision 208474)
+++ cp/semantics.c      (working copy)
@@ -7438,19 +7438,31 @@ retrieve_constexpr_fundef (tree fun)
 static bool
 is_valid_constexpr_fn (tree fun, bool complain)
 {
-  tree parm = FUNCTION_FIRST_USER_PARM (fun);
   bool ret = true;
-  for (; parm != NULL; parm = TREE_CHAIN (parm))
-    if (!literal_type_p (TREE_TYPE (parm)))
-      {
-       ret = false;
-       if (complain)
+
+  if (DECL_INHERITED_CTOR_BASE (fun)
+      && TREE_CODE (fun) == TEMPLATE_DECL)
+    {
+      ret = false;
+      if (complain)
+       error ("inherited constructors inherit %<constexpr%> from "
+              "the designated base");
+    }
+  else
+    {
+      for (tree parm = FUNCTION_FIRST_USER_PARM (fun);
+          parm != NULL_TREE; parm = TREE_CHAIN (parm))
+       if (!literal_type_p (TREE_TYPE (parm)))
          {
-           error ("invalid type for parameter %d of constexpr "
-                  "function %q+#D", DECL_PARM_INDEX (parm), fun);
-           explain_non_literal_class (TREE_TYPE (parm));
+           ret = false;
+           if (complain)
+             {
+               error ("invalid type for parameter %d of constexpr "
+                      "function %q+#D", DECL_PARM_INDEX (parm), fun);
+               explain_non_literal_class (TREE_TYPE (parm));
+             }
          }
-      }
+    }
 
   if (!DECL_CONSTRUCTOR_P (fun))
     {
Index: testsuite/g++.dg/cpp0x/inh-ctor19.C
===================================================================
--- testsuite/g++.dg/cpp0x/inh-ctor19.C (revision 0)
+++ testsuite/g++.dg/cpp0x/inh-ctor19.C (working copy)
@@ -0,0 +1,14 @@
+// PR c++/60389
+// { dg-do compile { target c++11 } }
+
+struct A
+{
+  template<typename...T> A(T...) {}
+};
+
+struct B : A
+{
+  using A::A;   // { dg-error "inherited" }
+};
+
+constexpr B b;  // { dg-error "literal" }