Use assoc int and float consts instead of module level ones
changelog: Recommend primitive type associated constants instead of module level constants
In Rust 1.43 integer and float primitive types will have a number of new associated constants. For example `MAX`, `MIN` and a number of constants related to the machine representation of floats. https://github.com/rust-lang/rust/pull/68952
These new constants are preferred over the module level constants in `{core,std}::{f*, u*, i*}`. I have in the last few days made sure that the documentation in the main rust repository uses the new constants in every place I could find (https://github.com/rust-lang/rust/pull/69860, https://github.com/rust-lang/rust/pull/70782). So the next step is naturally to make the linter recommend the new constants as well.
This PR only changes two lints. There are more. But I did not want the PR to be too big. And since I have not contributed to clippy before it felt saner to start with a small PR so I see if there are any quirks. More will come later.
rustup: update for the new Ty::walk interface.
The first commit fixes a portability bug in `setup-toolchain.sh`, while the second rewrites the handling of "trait impl methods" in `use_self` - even if `Ty::walk` could've still been used, it was IMO a misuse.
This could also serve as a PSA: *please* use `hir_ty_to_ty` instead of trying to compare `hir::Ty`s between themselves or against semantic `Ty`s. Its "quasi-deprecation" is 3 years old and doesn't really mean anything, just that it's currently uncached and that we should eventually querify it (either for a single HIR node, or for all of the nodes in an entire definition).
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changelog: none
Result<T, E> has an `ok()` method that adapts a Result<T,E> into an Option<T>.
It's possible to get around this adapter by writing Result<T,E>.map_or(None, Some).
This lint is implemented as a new variant of the existing
[`option_map_none` lint](https://github.com/rust-lang/rust-clippy/pull/2128)
Improve docs for option_option
Hint about using tri-state enums to replace legitimate uses of `Option<Option<_>>`
changelog: The docs for `option_option` now suggest using a tri-state enum
useless Rc<Rc<T>>, Rc<Box<T>>, Rc<&T>, Box<&T>
refers to #2394
changelog: Add lints for Rc<Rc<T>> and Rc<Box<T>> and Rc<&T>, Box<&T>
this is based on top of another change #5310 so probably should go after that one.
