Clippy Book Chapter Updates Reborn: Defining Lints
Revival of #9659, I've made a few changes (mainly ones from reviews from #9426, like removing mid-section storytelling) and some re-writes. The goal of the project would be to slowly re-write the Clippy book (only chapters that need it) to more up-to-date style.
## Notes
- Things like `git status` commands have changed, we need to make sure that they're correct.
- As this is a team-wide effort, I would please ask anyone and everyone to read it and give your opinion.
- To talk about the whole project, please use the tracking issue for the project #10597 (It also contains a timeline, discussions and more information)
---
changelog: Add a new "Defining lints" chapter to the book
r? `@flip1995`
Use ui_test's Windows path backslash heuristic
changelog: none
Instead of unconditionally replacing `\` with `/` we now use [`Match::PathBackslash`](https://docs.rs/ui_test/latest/ui_test/enum.Match.html#variant.PathBackslash) to only replace backslashes in paths that look like windows paths
`ui-toml` and `ui-cargo` tests still use the old way because they produce verbatim paths on windows in some tests (`\\?\C:\foo\...`) which was finnicky to get the replacement order correct with
Also removes the `ui_test` -> `compiletest` alias and `VarGuard`
allow calling `to_owned` on borrowed value for [`implicit_clone`]
fixes: #11281
a small and simple fix that give up checking for `referenced_value.to_owned()` usage.
changelog: allow calling `to_owned` with borrowed value for [`implicit_clone`]
[iter_overeager_cloned]: detect `.cloned().filter()` and `.cloned().find()`
changelog: [`iter_overeager_cloned`]: detect `.cloned().filter()` and `.cloned().find()`
Key idea:
```
// before
iter.cloned().filter(|x| unimplemented!() )
// after
iter.filter(|&x| unimplemented!() ).cloned()
// before
iter.cloned().filter( foo )
// after
// notice `iter` must be `Iterator<Item= &T>` (callee of `cloned()`)
// so the parameter in the closure of `filter` must be `&&T`
// so the deref is safe
iter.filter(|&x| foo(x) ).cloned()
```
Do not bless by default in ui tests
This restores the default behaviour to check the `.stderr`, it was changed in #11239 to bless by default in `cargo test` (unless in github actions), but check by default in `cargo uitest` which is fairly confusing
It also meant `cargo uitest -F internal` no longer worked
`--bless` prevents the use of `Args::test` but we can look at reintegrating with that after `@oli-obk's` vacation
r? `@flip1995`
changelog: none
Fix SPEEDTEST instructions and output
* `--nocapture` hasn't been needed anymore since forever (even before `ui_test`)
* the result was dividing by 1000 instead of the number of test runs, giving bogus (but still useful for the purpose) timing results.
changelog: fix SPEEDTEST instructions and output
Update ui test crate
This update also removes the `//`@run-rustfix`` flag, and just runs rustfix on all tests. This means I had to opt out of running rustfix on ~100 tests, but it also allowed me to remove the rustfix coverage check entirely, as it is now effectively builtin.
changelog: update ui-test crate to 0.13 (automatically runs rustfix on all tests)
redundant_locals: fix FPs on mutated shadows
Fixes#11290.
When a mutable binding is shadowed by
a mutable binding of the same name in a different scope, mutations in that scope have different meaning.
This PR fixes spurious `redundant_locals` emissions on such locals.
cc `@Centri3,` `@flip1995`
changelog: [`redundant_locals`]: fix false positives on mutated shadows
Rustup
r? `@ghost`
cc `@max-niederman` With the latest sync, I'm getting a lot of FP in the `redundant_locals` lint you recently added. Any ideas where this could come from?
changelog: none
When a mutable binding is shadowed by
a mutable binding of the same name in a different scope,
mutations in that scope have different meaning.
This commit fixes spurious `redundant_locals` emissions
on such locals.
[`filter_map_bool_then`]: Don't ICE on late bound regions
Fixes#11309
Also lints `&NonCopy` now, since any `&` is `Copy`. That was accidental, but it seems that this is a consequence (or improvement!) of this fix.
r? `@Jarcho`
changelog: [`filter_map_bool_then`]: Don't ICE on late bound regions
[`slow_vector_initialization`]: clarify why `Vec::new()` + resize is worse
#11198 extended this lint to also warn on `Vec::new()` + `resize(0, len)`, but did not update the lint documentation, so it left some confused (https://github.com/rust-lang/rust-clippy/issues/10938#issuecomment-1663880083).
This PR should make it a bit more clear. (cc `@djc` `@vi` what do you think about this?)
<details>
<summary>More details</summary>
Godbolt for `Vec::new()` + `.resize(x, 0)`: https://godbolt.org/z/e7q9xc9rG
The resize call first does a normal allocation (`__rust_alloc`):
```asm
alloc::raw_vec::finish_grow:
...
cmp qword ptr [rcx + 8], 0
je .LBB1_7 ; if capacity == 0 -> LBB1_7
.LBB1_7:
...
call qword ptr [rip + __rust_alloc@GOTPCREL]
```
*Then* a memset for zero initialization:
```asm
example::f:
...
xor esi, esi ; 0
call qword ptr [rip + memset@GOTPCREL]
```
------------
Godbolt for `vec![0; len]`: https://godbolt.org/z/M3vr53vWY
Important bit:
```asm
example::f:
...
call qword ptr [rip + __rust_alloc_zeroed@GOTPCREL]
```
</details>
changelog: [`slow_vector_initialization`]: clarify why `Vec::new()` + resize is worse than `vec![0; len]`
[`redundant_guards`]: don't lint on float literals
Fixes#11304
changelog: [`redundant_guards`]: don't lint on float literals
r? `@Centri3` i figured you are probably a good reviewer for this since you implemented the lint ^^
