PR c++/84489 - dependent default template argument

	* pt.c (type_unification_real): Handle early substitution failure.

From-SVN: r258039

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index dd35f1b..b2973d1 100644 (file)
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,8 @@
+2018-02-27  Jason Merrill  <jason@redhat.com>
+
+       PR c++/84489 - dependent default template argument
+       * pt.c (type_unification_real): Handle early substitution failure.
+
 2018-02-26  Jason Merrill  <jason@redhat.com>
 
        PR c++/84560 - ICE capturing multi-dimensional VLA.

diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 42fd872..a3da409 100644 (file)
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -19831,21 +19831,28 @@ type_unification_real (tree tparms,
            continue;
          tree parm = TREE_VALUE (tparm);
 
-         if (TREE_CODE (parm) == PARM_DECL
-             && uses_template_parms (TREE_TYPE (parm))
-             && saw_undeduced < 2)
-           continue;
+         tsubst_flags_t fcomplain = complain;
+         if (saw_undeduced == 1)
+           {
+             /* When saw_undeduced == 1, substitution into parm and arg might
+                fail or not replace all template parameters, and that's
+                fine.  */
+             fcomplain = tf_none;
+             if (TREE_CODE (parm) == PARM_DECL
+                 && uses_template_parms (TREE_TYPE (parm)))
+               continue;
+           }
 
          tree arg = TREE_PURPOSE (tparm);
          reopen_deferring_access_checks (*checks);
          location_t save_loc = input_location;
          if (DECL_P (parm))
            input_location = DECL_SOURCE_LOCATION (parm);
-         arg = tsubst_template_arg (arg, full_targs, complain, NULL_TREE);
-         if (!uses_template_parms (arg))
+         arg = tsubst_template_arg (arg, full_targs, fcomplain, NULL_TREE);
+         if (arg != error_mark_node && !uses_template_parms (arg))
            arg = convert_template_argument (parm, arg, full_targs, complain,
                                             i, NULL_TREE);
-         else if (saw_undeduced < 2)
+         else if (saw_undeduced == 1)
            arg = NULL_TREE;
          else
            arg = error_mark_node;

diff --git a/gcc/testsuite/g++.dg/cpp0x/fntmpdefarg7.C b/gcc/testsuite/g++.dg/cpp0x/fntmpdefarg7.C
new file mode 100644 (file)
index 0000000..636bf1a
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/fntmpdefarg7.C
@@ -0,0 +1,10 @@
+// PR c++/84489
+// { dg-do compile { target c++11 } }
+
+template <class T = int, T N = T(), bool B = (N >> 1)>
+T f1() {return 0;}
+
+int main()
+{
+  f1(); // Bug here
+}