re PR c++/23055 (overload resolution does not find templated function (zero -> pointer))

	PR c++/23055
	* pt.c (uses_deducible_template_parms): New.
	(deducible_array_bound, deducible_expression): New.
	(deducible_template_args): New.
	(unify_one_argument): Call uses_deducible_template_parms.

From-SVN: r197790

2 files changed, 149 insertions, 1 deletions

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 01fc3ef..f1cf2ce 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,11 @@
+2013-04-11  Jason Merrill  <jason@redhat.com>
+
+	PR c++/23055
+	* pt.c (uses_deducible_template_parms): New.
+	(deducible_array_bound, deducible_expression): New.
+	(deducible_template_args): New.
+	(unify_one_argument): Call uses_deducible_template_parms.
+
 2013-04-11  Paolo Carlini  <paolo.carlini@oracle.com>
 
 	PR c++/56913
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 1d429fe..5bb0cc0 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -15357,6 +15357,135 @@ check_non_deducible_conversion (tree parm, tree arg, int strict,
     return unify_arg_conversion (explain_p, parm, type, arg);
 }
 
+static bool uses_deducible_template_parms (tree type);
+
+/* Returns true iff the expression EXPR is one from which a template
+   argument can be deduced.  In other words, if it's an undecorated
+   use of a template non-type parameter.  */
+
+static bool
+deducible_expression (tree expr)
+{
+  return (TREE_CODE (expr) == TEMPLATE_PARM_INDEX);
+}
+
+/* Returns true iff the array domain DOMAIN uses a template parameter in a
+   deducible way; that is, if it has a max value of <PARM> - 1.  */
+
+static bool
+deducible_array_bound (tree domain)
+{
+  if (domain == NULL_TREE)
+    return false;
+
+  tree max = TYPE_MAX_VALUE (domain);
+  if (TREE_CODE (max) != MINUS_EXPR)
+    return false;
+
+  return deducible_expression (TREE_OPERAND (max, 0));
+}
+
+/* Returns true iff the template arguments ARGS use a template parameter
+   in a deducible way.  */
+
+static bool
+deducible_template_args (tree args)
+{
+  for (int i = 0; i < TREE_VEC_LENGTH (args); ++i)
+    {
+      bool deducible;
+      tree elt = TREE_VEC_ELT (args, i);
+      if (ARGUMENT_PACK_P (elt))
+	deducible = deducible_template_args (ARGUMENT_PACK_ARGS (elt));
+      else
+	{
+	  if (PACK_EXPANSION_P (elt))
+	    elt = PACK_EXPANSION_PATTERN (elt);
+	  if (TREE_CODE (elt) == TEMPLATE_TEMPLATE_PARM)
+	    deducible = true;
+	  else if (TYPE_P (elt))
+	    deducible = uses_deducible_template_parms (elt);
+	  else
+	    deducible = deducible_expression (elt);
+	}
+      if (deducible)
+	return true;
+    }
+  return false;
+}
+
+/* Returns true iff TYPE contains any deducible references to template
+   parameters, as per 14.8.2.5.  */
+
+static bool
+uses_deducible_template_parms (tree type)
+{
+  if (PACK_EXPANSION_P (type))
+    type = PACK_EXPANSION_PATTERN (type);
+
+  /* T
+     cv-list T
+     TT<T>
+     TT<i>
+     TT<> */
+  if (TREE_CODE (type) == TEMPLATE_TYPE_PARM
+      || TREE_CODE (type) == BOUND_TEMPLATE_TEMPLATE_PARM)
+    return true;
+
+  /* T*
+     T&
+     T&&  */
+  if (POINTER_TYPE_P (type))
+    return uses_deducible_template_parms (TREE_TYPE (type));
+
+  /* T[integer-constant ]
+     type [i]  */
+  if (TREE_CODE (type) == ARRAY_TYPE)
+    return (uses_deducible_template_parms (TREE_TYPE (type))
+	    || deducible_array_bound (TYPE_DOMAIN (type)));
+
+  /* T type ::*
+     type T::*
+     T T::*
+     T (type ::*)()
+     type (T::*)()
+     type (type ::*)(T)
+     type (T::*)(T)
+     T (type ::*)(T)
+     T (T::*)()
+     T (T::*)(T) */
+  if (TYPE_PTRMEM_P (type))
+    return (uses_deducible_template_parms (TYPE_PTRMEM_CLASS_TYPE (type))
+	    || (uses_deducible_template_parms
+		(TYPE_PTRMEM_POINTED_TO_TYPE (type))));
+
+  /* template-name <T> (where template-name refers to a class template)
+     template-name <i> (where template-name refers to a class template) */
+  if (CLASS_TYPE_P (type)
+      && CLASSTYPE_TEMPLATE_INFO (type)
+      && PRIMARY_TEMPLATE_P (CLASSTYPE_TI_TEMPLATE (type)))
+    return deducible_template_args (INNERMOST_TEMPLATE_ARGS
+				    (CLASSTYPE_TI_ARGS (type)));
+
+  /* type (T)
+     T()
+     T(T)  */
+  if (TREE_CODE (type) == FUNCTION_TYPE
+      || TREE_CODE (type) == METHOD_TYPE)
+    {
+      if (uses_deducible_template_parms (TREE_TYPE (type)))
+	return true;
+      tree parm = TYPE_ARG_TYPES (type);
+      if (TREE_CODE (type) == METHOD_TYPE)
+	parm = TREE_CHAIN (parm);
+      for (; parm; parm = TREE_CHAIN (parm))
+	if (uses_deducible_template_parms (TREE_VALUE (parm)))
+	  return true;
+    }
+
+  return false;
+}
+
 /* Subroutine of type_unification_real and unify_pack_expansion to
    handle unification of a single P/A pair.  Parameters are as
    for those functions.  */
@@ -15376,10 +15505,21 @@ unify_one_argument (tree tparms, tree targs, tree parm, tree arg,
        template args from other function args.  */
     return unify_success (explain_p);
 
-  /* FIXME uses_deducible_template_parms */
+  /* Implicit conversions (Clause 4) will be performed on a function
+     argument to convert it to the type of the corresponding function
+     parameter if the parameter type contains no template-parameters that
+     participate in template argument deduction.  */
   if (TYPE_P (parm) && !uses_template_parms (parm))
+    /* For function parameters that contain no template-parameters at all,
+       we have historically checked for convertibility in order to shortcut
+       consideration of this candidate.  */
     return check_non_deducible_conversion (parm, arg, strict, flags,
 					   explain_p);
+  else if (strict == DEDUCE_CALL
+	   && TYPE_P (parm) && !uses_deducible_template_parms (parm))
+    /* For function parameters with only non-deducible template parameters,
+       just return.  */
+    return unify_success (explain_p);
 
   switch (strict)
     {