Add map_err_ignore lint
In a large code base a lot of times errors are ignored by using something like:
```rust
foo.map_err(|_| Some::Enum)?;
```
This drops the original error in favor of a enum that will not have the original error's context. This lint helps catch throwing away the original error in favor of an enum without its context.
---
*Please keep the line below*
changelog: Added map_err_ignore lint
Add a new lint, `manual-strip`, that suggests using the `str::strip_prefix`
and `str::strip_suffix` methods introduced in Rust 1.45 when the same
functionality is performed 'manually'.
Closes#5734
Add lint panic in result
### Change
Adding a new "restriction" lint that will emit a warning when using "panic", "unimplemented" or "unreachable" in a function of type option/result.
### Motivation
Some codebases must avoid crashes at all costs, and hence functions of type option/result must return an error instead of crashing.
### Test plan
Running:
TESTNAME=panic_in_result cargo uitest ---
changelog: none
This catches bugs of the form
tokio::spawn(async move {
let f = some_async_thing();
f // Oh no I forgot to await f so that work will never complete.
});
Warn about assignments where left-hand side place expression is the same
as right-hand side value expression. For example, warn about assignment in:
```rust
pub struct Event {
id: usize,
x: i32,
y: i32,
}
pub fn copy_position(a: &mut Event, b: &Event) {
a.x = b.x;
a.y = a.y;
}
```
This lint catches cases where the last statement of a closure expecting
an instance of Ord has a trailing semi-colon. It compiles since the
closure ends up return () which also implements Ord but causes
unexpected results in cases such as sort_by_key.
Fixes#5080
reprise: rebase, update and address all concerns
New lint: iter_next_slice
Hello, this is a work-in-progress PR for issue: https://github.com/rust-lang/rust-clippy/issues/5572
I have implemented lint to replace `iter().next()` for `slice[index..]` and `array` with `get(index)` and `get(0)` respectively. However since I made a lot of changes, I would like to request some feedback before continuing so that I could fix mistakes.
Thank you!
---
changelog: implement `iter_next_slice` lint and test, and modify `needless_continues`, `for_loop_over_options_result` UI tests since they have `iter().next()`
New lint: `match_wildcard_for_single_variants`
changelog: Added a new lint match_wildcard_for_single_variants to warn on enum matches where a wildcard is used to match a single variant
Closes#5556
Rename lint `identity_conversion` to `useless_conversion`
Lint name `identity_conversion` was misleading, so this PR renames it to `useless_conversion`.
As decision has not really came up in the issue comments, this PR will probably need discussion.
fixes#3106
changelog: Rename lint `identity_conversion` to `useless_conversion`
New lint `match_vec_item`
Added new lint to warn a match on index item which can panic. It's always better to use `get(..)` instead.
Closes#5500
changelog: New lint `match_on_vec_items`
Fixes#4226
This introduces the lint await_holding_lock. For async functions, we iterate
over all types in generator_interior_types and look for types named MutexGuard,
RwLockReadGuard, or RwLockWriteGuard. If we find one then we emit a lint.
If let else mutex
changelog: Adds lint to catch incorrect use of `Mutex::lock` in `if let` expressions with lock calls in any of the blocks.
closes: #5219
Add lint on large non scalar const
This PR adds the new lint `non_scalar_const` that aims to warn against `const` declaration of large arrays. For performance, because of inlining, large arrays should be preferably declared as `static`.
Note: i made this one to warn on all const arrays, whether they are in a body function or not. I don't know if this is really necessary, i could just reduce this lint to variables out of function scope.
Fixes: #400
changelog: add new lint for large non-scalar types declared as const
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)
