std::ops::Slice is not in the prelude

[SimonSapin]

The slice and related methods of &[T] apparently have moved to the std::ops::Slice trait, but that trait is not in the prelude. This leads to errors such as:

error: type `&[u8]` does not implement any method in scope named `slice`

This can be “fixed” by adding use std::ops::Slice everywhere, but that doesn’t seem like the intended behavior.

[pnkfelix]

I believe this was injected by PR #17620

cc @nick29581

[nrc]

You should use the slicing notation instead of the slice methods.

[SimonSapin]

Sure, eventually. But going straight to a build error without a deprecation period nor an error message that indicates what to do is unusual for Rust, even pre-1.0.

[pnkfelix]

@nick29581 I thought the sugar was feature gated. Was the gate removed?

[nrc]

@pnkfelix I believe it was as part of @aturon's backout, but I didn't check and if it was, it was unintentional.

@SimonSapin hard to make an error message for this, since it is just a missing method, but I think we are going to try a smoother deprecation approach

[SimonSapin]

@nick29581 My understanding is that so far, stuff we want people not to use should be marked as deprecated (to emit a warning) with a message indicating the alternative, and not removed from some time (possibly until 1.0).