Clang sendability audit for closures

Development Compiler
1

Today, when you use NS_HEADER_AUDIT_BEGIN(nullability, sendability), closures are also assumed to be non-sendable. This is very optimistic, and kind of opposite to how escaping works. Obj-C closures are assumed to be escaping, and have to be opted in via __attribute__((noescape)).

Looking more closely at the macro, it appears there's quite a bit of power here:

"clang attribute NS_HEADER_AUDIT_sendability.push (__attribute__((swift_attr(\"@_nonSendable(_assumed)\"))), apply_to = any(objc_interface, record, enum))"

Is it possible to construct a pragma that would import closures to be @Sendable such that they could then then be opted-out on a case-by-case basis using __attribute__((swift_attr("@_nonSendable")))?

2

I feel like I'm getting closer, but I cannot figure out how to use the apply_to field correctly.

Both of these produce a warning:
apply_to = block
apply_to = any(block)

Unused attribute 'swift_attr' in '#pragma clang attribute push' region

If I combine this with objc_interface, I get no warning, but also don't get the bahavior I want. The attribute is correctly applied to the ObjC interfaces, but not to imported blocks.

apply_to = any(objc_interface, block)