SE-0326: Multi-statement closure parameter/result type inference

[benrimmington]

@ExFalsoQuodlibet

I'm trying to test this with the toolchain linked in the proposal and the flags, but it's not working.

I think you'll need a more recent snapshot, so I've updated the proposal.

• The old toolchain was created on 2021-10-05
• The implementation was merged on 2021-10-09

Luckily, the downloads should be faster now!