8168774: Polymorhic signature method check crashes javac
Summary: Check for polysig method assumes arity is greater than zero
Reviewed-by: vromero
T4720359a.java:16:23: compiler.err.override.incompatible.ret: (compiler.misc.cant.hide: m(), p1.T4720359c, m(), p1.T4720359a), int, void
1 error