c++: Fix ICE on valid involving variadic constructor [PR111592]

We currently ICE upon the following valid code, due to the fix made through
commit 9efe5fbde1e8

=== cut here ===
struct ignore { ignore(...) {} };
template<class... Args>
void InternalCompilerError(Args... args)
{ ignore{ ignore(args) ... }; }
int main() { InternalCompilerError(0, 0); }
=== cut here ===

Change 9efe5fbde1e8 avoids infinite recursion in build_over_call by returning
error_mark_node if one invokes ignore::ignore(...) with an argument of type
ignore, because otherwise we end up calling convert_arg_to_ellipsis for that
argument, and recurse into build_over_call with the exact same parameters.

This patch tightens the condition to only return error_mark_node if there's one
and only one parameter to the call being processed - otherwise we won't
infinitely recurse.

Successfully tested on x86_64-pc-linux-gnu.

	PR c++/111592

gcc/cp/ChangeLog:

	* call.cc (build_over_call): Only error out if there's a single
	parameter of type A in a call to A::A(...).

gcc/testsuite/ChangeLog:

	* g++.dg/cpp0x/variadic186.C: New test.

1 files changed, 11 insertions, 0 deletions

diff --git a/gcc/testsuite/g++.dg/cpp0x/variadic186.C b/gcc/testsuite/g++.dg/cpp0x/variadic186.C
new file mode 100644
index 0000000..4a25a1a
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/variadic186.C
@@ -0,0 +1,11 @@
+// PR c++/111592
+// { dg-do compile { target c++11 } }
+
+struct ignore { ignore(...) {} };
+
+template<class... Args>
+void InternalCompilerError(Args... args)
+{ ignore{ ignore(args) ... }; }
+
+int main()
+{ InternalCompilerError(0, 0); }