Trailing commas are not allowed in closure types

[ftxqxd]

The following code:

let x: |int,|;

does not parse. It should be noted that this already works with closure expressions (e.g., let x = |x: int,| 1i;).

[untitaker]

Seems fixed by #19413. Can this be closed?

[ftxqxd]

This shouldn’t be fixed by #19413. I explicitly didn’t fix it because I suspect it’s not going to be easy and, with unboxed closures, will be irrelevant anyway.

[kmcallister]

Old-style closures have been removed.