Please see the code: https://github.com/rust-lang/rust/blob/68650cacf23c60ee2f346b27bcefa7c6c31de1e4/src/librustc/ty/context.rs#L1532-L1575 https://github.com/r

Please see the code: https://github.com/rust-lang/rust/blob/68650cacf23c60ee2f346b27bcefa7c6c31de1e4/src/librustc/ty/context.rs#L1532-L1575 https://github.com/rust-lang/rust/blob/68650cacf23c60ee2f346... In edition 2018, migration mode is turned on. I learned myself about this today btw, after I saw this PR: https://github.com/rust-lang/rust/pull/58342 https://github.com/rust-lang/rust/pull/58342 I think I was mistaken about one point though which is that migration mode is erroring if one of the two errors. IIRC migration mode was introduced that way but it seems to have been changed to be a bit more tolerant than AST borrowck. Anyways, more NLL fun is to come, and it's to come to both editions.