Implement the manual_non_exhaustive lint
Some implementation notes:
* Not providing automatic fixups because additional changes may be needed in other parts of the code, e.g. when constructing a struct.
* Even though the attribute is valid on enum variants, it's not possible to use the manual implementation of the pattern because the visibility is always public, so the lint ignores enum variants.
* Unit structs are also ignored, it's not possible to implement the pattern manually without fields.
* The attribute is not accepted in unions, so those are ignored too.
* Even though the original issue did not mention it, tuple structs are also linted because it's possible to apply the pattern manually.
changelog: Added the manual non-exhaustive implementation lint
Closes#2017
Fix the bugs of `manual_memcpy`, simplify the suggestion and refactor it
While I’m working on the long procrastinated work to expand `manual_memcpy`(#1670), I found a few minor bugs and probably unidiomatic or old coding style. There is a brief explanation of changes to the behaviour this PR will make below. And, I have a questoin: do I need to add tests for the first and second fixed bugs? I thought it might be too rare cases to include the tests for those. I added for the last one though.
* Bug fix
* It negates resulted offsets (`src/dst_offset`) when `offset` is subtraction by 0. This PR will remove any subtraction by 0 as a part of minification.
```rust
for i in 0..5 {
dst[i - 0] = src[i];
}
```
```diff
warning: it looks like you're manually copying between slices
--> src/main.rs:2:14
|
LL | for i in 0..5 {
- | ^^^^ help: try replacing the loop by: `dst[..-5].clone_from_slice(&src[..5])`
+ | ^^^^ help: try replacing the loop by: `dst[..5].clone_from_slice(&src[..5])`
|
```
* It prints `RangeTo` or `RangeFull` when both of `end` and `offset` are 0, which have different meaning. This PR will print 0. I could reject the cases `end` is 0, but I thought I won’t catch other cases `reverse_range_loop` will trigger, and it’s over to catch every such cases.
```rust
for i in 0..0 {
dst[i] = src[i];
}
```
```diff
warning: it looks like you're manually copying between slices
--> src/main.rs:2:14
|
LL | for i in 0..0 {
- | ^^^^ help: try replacing the loop by: `dst.clone_from_slice(&src[..])`
+ | ^^^^ help: try replacing the loop by: `dst[..0].clone_from_slice(&src[..0])`
|
```
* it prints four dots when `end` is `None`. This PR will ignore any `for` loops without `end` because a `for` loop that takes `RangeFrom` as its argument and contains indexing without the statements or the expressions that end loops such as `break` will definitely panic, and `manual_memcpy` should ignore the loops with such control flow.
```rust
fn manual_copy(src: &[u32], dst: &mut [u32]) {
for i in 0.. {
dst[i] = src[i];
}
}
```
```diff
-warning: it looks like you're manually copying between slices
- --> src/main.rs:2:14
- |
-LL | for i in 0.. {
- | ^^^ help: try replacing the loop by: `dst[....].clone_from_slice(&src[....])`
- |
```
* Simplification of the suggestion
* It prints 0 when `start` or `end` and `offset` are same (from #3323). This PR will use `RangeTo`
changelog: fixed the bugs of `manual_memcpy` and also simplify the suggestion.
Fixed incorrect suggestion of `clone_double_ref` lint
- Added `<_>` to suggestion
- Changed help message
- Added new tests
Closes#5494
changelog: Improve suggestion of [`clone_double_ref`]
Current example is incorrect (or pseudo-code) because a struct name is omitted. I have used the code from the tests instead. Perhaps this example can be made less verbose, but I think it is more convenient to see a "real" code as an example.
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`
Implement mismatched_target_os lint
I've extended the check suggested in the issue to all the currently supported operating systems instead of limiting it to `linux` and `macos`, let me know if we want to do this.
Also, I've restored the text `There are over XXX lints ...` in the README as it was matched against by `cargo dev new_lint`.
changelog: Added `mismatched_target_os` lint to warn when an operating system is used in target family position in a #[cfg] attribute
Closes#3949
- Show just one error message with multiple suggestions in case of
using multiple times an OS in target family position
- Only suggest #[cfg(unix)] when the OS is in the Unix family
- Test all the operating systems
