Panic on expected interface method implemented as internal.

[AlbertoCentonze]

Version Information

• vyper Version: 0.4.1+commit.f92ef414a

What's your issue about?

Given an interface file foo.vyi

@external
def bar():
    ...

if the interface is imported and implemented in a module:

import foo

implements: foo


# !!!! here we don't add the external modifier
def bar():
    pass

Not using the external modifier makes the compiler panic.

[charles-cooper]

we should really not require any visibility modifier in .vyi files (everything is external)