JLS SE 7 states:

A method is signature polymorphic if and only if all of the following conditions hold:

• It is declared in the java.lang.invoke.MethodHandle class.
• It takes a single variable arity parameter (§8.4.1) whose declared type is Object[].
• It has a return type of Object.
• It is native


Internally, the compiler uses a diferent way of detecting signature polymorphic methods (the special @PolymorphicSignature) - we should update the compiler to use the same JLS logic.