I checked with t-libs to make sure this is OK to do on stable functions: https://rust-lang.zulipchat.com/#narrow/stream/219381-t-libs/topic/Replacing.20std.20function.20arg.20type.20with.20private.20type.20def.3F
I checked with t-libs to make sure this is OK to do on stable functions: https://rust-lang.zulipchat.com/#narrow/stream/219381-t-libs/topic/Replacing.20std.20function.20arg.20type.20with.20private.20type.20def.3F