The issue here was that when processing the explicit template args in
fn_type_unification we added an empty argument pack for the parameter pack,
so we never tried to do any deduction for it, and therefore never looked at
its type. We need that empty pack behavior for partial ordering, but we
don't want it here, so let's make it conditional on tf_partial.
Tested x86_64-pc-linux-gnu, applying to trunk.
* pt.c (coerce_template_parms): Don't add an empty pack if
tf_partial.
(fn_type_unification): Pass tf_partial to coerce_template_parms.
---
gcc/cp/pt.c | 3 ++-
gcc/testsuite/g++.dg/cpp0x/sfinae65.C | 15 +++++++++++++++
gcc/cp/ChangeLog | 5 +++++
3 files changed, 22 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/g++.dg/cpp0x/sfinae65.C
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 05d5371d8a6..dc982f3ed55 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -8436,6 +8436,7 @@ coerce_template_parms (tree parms,
arg = NULL_TREE;
if (template_parameter_pack_p (TREE_VALUE (parm))
+ && (arg || !(complain & tf_partial))
&& !(arg && ARGUMENT_PACK_P (arg)))
{
/* Some arguments will be placed in the
@@ -20077,7 +20078,7 @@ fn_type_unification (tree fn,
substitution context. */
explicit_targs
= (coerce_template_parms (tparms, explicit_targs, NULL_TREE,
- complain,
+ complain|tf_partial,
/*require_all_args=*/false,
/*use_default_args=*/false));
if (explicit_targs == error_mark_node)
diff --git a/gcc/testsuite/g++.dg/cpp0x/sfinae65.C
b/gcc/testsuite/g++.dg/cpp0x/sfinae65.C
new file mode 100644
index 00000000000..66790df77c6
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/sfinae65.C
@@ -0,0 +1,15 @@
+// PR c++/86932
+// { dg-do compile { target c++11 } }
+
+template<bool, typename T> struct enable_if { using type = T; };
+template<typename T> struct enable_if<false, T> { };
+
+template<typename> struct is_foo { static constexpr bool value = false; };
+
+// { dg-error "enable_if" "" { target *-*-* } .+1 }
+template<class U, typename enable_if<is_foo<U>::value, int>::type...> void f()
{}
+
+int main()
+{
+ f<int>(); // { dg-error "no match" }
+}
diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 550b7541d9f..bce9b108723 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,5 +1,10 @@
2019-03-26 Jason Merrill <ja...@redhat.com>
+ PR c++/86932 - missed SFINAE with empty pack.
+ * pt.c (coerce_template_parms): Don't add an empty pack if
+ tf_partial.
+ (fn_type_unification): Pass tf_partial to coerce_template_parms.
+
PR c++/86429 - constexpr variable in lambda.
PR c++/82643
PR c++/87327
base-commit: 496d55fdc6a7305f342a814f51482df29b1ce4f9
--
2.20.1
