c++: CWG2235 partial ordering and non-dependent types

Issue 2235 removed the rule previously added for issues 1391/1847 that had
partial ordering completely ignore function parameters with no deducible
template parameters.

gcc/cp/ChangeLog
2020-05-05  Jason Merrill  <jason@redhat.com>

	CWG 2235
	* pt.c (more_specialized_fn): Do consider parms with no deducible
	template parameters.

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 71ca21f..c49e90e 100644 (file)
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,5 +1,11 @@
 2020-05-05  Jason Merrill  <jason@redhat.com>
 
+       CWG 2235
+       * pt.c (more_specialized_fn): Do consider parms with no deducible
+       template parameters.
+
+2020-05-05  Jason Merrill  <jason@redhat.com>
+
        PR c++/90212
        * constexpr.c (potential_constant_expression_1): In a lambda
        function, consider a captured variable directly.

diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index ff8391c..2ed6d0e 100644 (file)
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -23960,13 +23960,6 @@ more_specialized_fn (tree pat1, tree pat2, int len)
           len = 0;
         }
 
-      /* DR 1847: If a particular P contains no template-parameters that
-        participate in template argument deduction, that P is not used to
-        determine the ordering.  */
-      if (!uses_deducible_template_parms (arg1)
-         && !uses_deducible_template_parms (arg2))
-       goto next;
-
       if (TYPE_REF_P (arg1))
        {
          ref1 = TYPE_REF_IS_RVALUE (arg1) + 1;
@@ -24088,8 +24081,6 @@ more_specialized_fn (tree pat1, tree pat2, int len)
           These must be unordered.  */
        break;
 
-    next:
-
       if (TREE_CODE (arg1) == TYPE_PACK_EXPANSION
           || TREE_CODE (arg2) == TYPE_PACK_EXPANSION)
         /* We have already processed all of the arguments in our

diff --git a/gcc/testsuite/g++.dg/template/partial-order1.C b/gcc/testsuite/g++.dg/template/partial-order1.C
index 0832ea5..624bb4b 100644 (file)
--- a/gcc/testsuite/g++.dg/template/partial-order1.C
+++ b/gcc/testsuite/g++.dg/template/partial-order1.C
@@ -14,5 +14,5 @@ void f(typename A<T>::size_type, T);
 
 int main()
 {
-  f(1,2);                      // { dg-error "ambiguous" }
+  f(1,2);
 }

diff --git a/gcc/testsuite/g++.dg/template/partial-order2.C b/gcc/testsuite/g++.dg/template/partial-order2.C
new file mode 100644 (file)
index 0000000..2aed600
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/partial-order2.C
@@ -0,0 +1,20 @@
+// CWG 2235
+
+namespace X
+{
+  template<typename T> struct Const { typedef void type; };
+  template<typename T> void f(T, typename Const<T>::type*); // T1
+  template<typename T> void f(T, void *); // T2
+  void g(void *p) { f(0, p); }
+}
+
+namespace Y
+{
+  struct A { A(int); };
+  struct B { B(int); };
+
+  template<typename T> void f(T, A);
+  template<typename T> void f(T*, B);
+
+  void g(int *p) { f(p, 0); }  // { dg-error "ambiguous" }
+}