…turn

During development, a function could have a return type set that is a
bare trait object by accident. We already suggest using either a boxed
trait object or `impl Trait` if the return paths will allow it. We now
do so too when there are *no* return paths or they all resolve to `!`.
We still don't handle cases where the trait object is *not* the entirety
of the return type gracefully.

When the return type is `!Sized` we look for all the returned
expressions in the body to fetch their types and provide a reasonable
suggestion. The tail expression of the body is normally evaluated after
checking whether the return type is `Sized`. Changing the order of the
evaluation produces undesirable knock down effects, so we detect the
specific case that newcomers are likely to encounter ,returning a single
bare trait object, and only in that case we evaluate the tail
expression's type so that the suggestion will be accurate.

…n, r=varkor

Suggest `-> impl Trait` and `-> Box<dyn Trait>` on fn that doesn't return

During development, a function could have a return type set that is a
bare trait object by accident. We already suggest using either a boxed
trait object or `impl Trait` if the return paths will allow it. We now
do so too when there are *no* return paths or they all resolve to `!`.
We still don't handle cases where the trait object is *not* the entirety
of the return type gracefully.

Closes rust-lang#38376.

Remove unused rustc_serialize::hex module

* Remove unused `rustc_serialize::hex` module
* Cleanup `Cargo.toml`

Use assoc int consts3

Define module level int consts with associated constants instead of `min_value()` and `max_value()`. So the code become consistent with what the docs recommend etc. Seems natural.

Also remove the last usages of the int module constants from this repo (except src/test/ directory which I have still not really done anything in). Some places were missed in the previous PRs because the code uses `crate::<IntTy>` to reach the constants.

This is a continuation of rust-lang#70857

r? @dtolnay

…r=estebank

Fix #! (shebang) stripping account space issue

 rust-lang#70528

…imulacrum

Fix stage0.txt version number comment

r? @Mark-Simulacrum

Fix incorrect description of E0690

r? @steveklabnik

Clean up E0554 explanation

r? @Dylan-DPC