Bare trait object edge with leading paren

[harpocrates]

The following test case (taken from rustc's testsuite) doesn't parse:

// build-pass (FIXME(62277): could be check-pass?)

#![allow(bare_trait_objects)]

type A = Box<(Fn(u8) -> u8) + 'static + Send + Sync>; // OK (but see #39318)

fn main() {}

Besides being already controversial (check out the issue referenced) and one hell of an edge case, bare trait objects are on their way out.