Uplift `clippy::for_loops_over_fallibles` lint into rustc
This PR, as the title suggests, uplifts [`clippy::for_loops_over_fallibles`] lint into rustc. This lint warns for code like this:
```rust
for _ in Some(1) {}
for _ in Ok::<_, ()>(1) {}
```
i.e. directly iterating over `Option` and `Result` using `for` loop.
There are a number of suggestions that this PR adds (on top of what clippy suggested):
1. If the argument (? is there a better name for that expression) of a `for` loop is a `.next()` call, then we can suggest removing it (or rather replacing with `.by_ref()` to allow iterator being used later)
```rust
for _ in iter.next() {}
// turns into
for _ in iter.by_ref() {}
```
2. (otherwise) We can suggest using `while let`, this is useful for non-iterator, iterator-like things like [async] channels
```rust
for _ in rx.recv() {}
// turns into
while let Some(_) = rx.recv() {}
```
3. If the argument type is `Result<impl IntoIterator, _>` and the body has a `Result<_, _>` type, we can suggest using `?`
```rust
for _ in f() {}
// turns into
for _ in f()? {}
```
4. To preserve the original behavior and clear intent, we can suggest using `if let`
```rust
for _ in f() {}
// turns into
if let Some(_) = f() {}
```
(P.S. `Some` and `Ok` are interchangeable depending on the type)
I still feel that the lint wording/look is somewhat off, so I'll be happy to hear suggestions (on how to improve suggestions :D)!
Resolves#99272
[`clippy::for_loops_over_fallibles`]: https://rust-lang.github.io/rust-clippy/master/index.html#for_loops_over_fallibles
rename `ImplItemKind::TyAlias` to `ImplItemKind::Type`
The naming of this variant seems inconsistent given that this is not really a "type alias", and the associated type variant for `TraitItemKind` is just called `Type`.
Remove `mir::CastKind::Misc`
As discussed in #97649 `mir::CastKind::Misc` is not clear, this PR addresses that by creating a new enum variant for every valid cast.
r? ````@oli-obk````
Move lint level source explanation to the bottom
So, uhhhhh
r? `@estebank`
## User-facing change
"note: `#[warn(...)]` on by default" and such are moved to the bottom of the diagnostic:
```diff
- = note: `#[warn(unsupported_calling_conventions)]` on by default
= warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
= note: for more information, see issue #87678 <https://github.com/rust-lang/rust/issues/87678>
+ = note: `#[warn(unsupported_calling_conventions)]` on by default
```
Why warning is enabled is the least important thing, so it shouldn't be the first note the user reads, IMO.
## Developer-facing change
`struct_span_lint` and similar methods have a different signature.
Before: `..., impl for<'a> FnOnce(LintDiagnosticBuilder<'a, ()>)`
After: `..., impl Into<DiagnosticMessage>, impl for<'a, 'b> FnOnce(&'b mut DiagnosticBuilder<'a, ()>) -> &'b mut DiagnosticBuilder<'a, ()>`
The reason for this is that `struct_span_lint` needs to edit the diagnostic _after_ `decorate` closure is called. This also makes lint code a little bit nicer in my opinion.
Another option is to use `impl for<'a> FnOnce(LintDiagnosticBuilder<'a, ()>) -> DiagnosticBuilder<'a, ()>` altough I don't _really_ see reasons to do `let lint = lint.build(message)` everywhere.
## Subtle problem
By moving the message outside of the closure (that may not be called if the lint is disabled) `format!(...)` is executed earlier, possibly formatting `Ty` which may call a query that trims paths that crashes the compiler if there were no warnings...
I don't think it's that big of a deal, considering that we move from `format!(...)` to `fluent` (which is lazy by-default) anyway, however this required adding a workaround which is unfortunate.
## P.S.
I'm sorry, I do not how to make this PR smaller/easier to review. Changes to the lint API affect SO MUCH 😢
`Res::SelfTy` currently has two `Option`s. When the second one is `Some`
the first one is never consulted. So we can split it into two variants,
`Res::SelfTyParam` and `Res::SelfTyAlias`, reducing the size of `Res`
from 24 bytes to 12. This then shrinks `hir::Path` and
`hir::PathSegment`, which are the HIR types that take up the most space.
Stabilize const `BTree{Map,Set}::new`
The FCP was completed in #71835.
Since `len` and `is_empty` are not const stable yet, this also creates a new feature for them since they previously used the same `const_btree_new` feature.
fix a ui test
use `into`
fix clippy ui test
fix a run-make-fulldeps test
implement `IntoQueryParam<DefId>` for `OwnerId`
use `OwnerId` for more queries
change the type of `ParentOwnerIterator::Item` to `(OwnerId, OwnerNode)`
Always print '_, even for erased lifetimes.
Explicit lifetime arguments are now the recommended syntax in rust 2018 and rust 2021. This PR applies this discipline to rustc itself.
Since clippy can use a projects MSRV for its lints, it might not want
to consider functions as const stable if they have been added lately.
Functions that have been stabilized this version use
CURRENT_RUSTC_VERSION as their version, which gets then turned into the
current version, which might be something like `1.66.0-dev`. The version
parser cannot deal with this version, so it has to be stripped off.
Since `len` and `is_empty` are not const stable yet, this also
creates a new feature for them since they previously used the same
`const_btree_new` feature.
Introduce mir::Unevaluated
Previously the distinction between unevaluated constants in the type-system and in mir was not explicit and a little confusing. Probably better to introduce its own type for that.
r? `@lcnr`
