RFC: bare-ffi-lambdas

[Theodus]

Adds "bare" lambdas for use in FFI interoperation with C libraries that use function pointers as callbacks: https://github.com/ponylang/rfcs/blob/master/text/0034-bare-ffi-lambdas.md

[Praetonus]

Something from the RFC is unclear to me.

class Foo
  fun @foo() => None

Foo.foo()

In this example, should Foo.foo()

1. be generated as a direct call to the function?
2. be sugared as Foo.create().foo()?
3. result in a compilation error?

[jemc]

Good question. That may not have been clearly defined in the RFC, but we can take a stab at defining it now.

1. be generated as a direct call to the function?

This makes sense to me, given that an instance of Foo is not required for invoking the function. So, "bare" functions would be executable both on a type, or on an instance, much like constructors are.

[Praetonus]

Yeah that makes sense.