Rework suggestion generation of `unit_arg` lint
Found this bug while running `cargo fix --clippy` on quite a big codebase:
This would replace something like:
```rust
Some(fn_that_actually_does_something(&a, b))
```
with
```rust
Some(())
```
which obviously suppresses side effects.
Since pretty much every expression could have side effects, I think making this suggestion `MaybeIncorrect` is the best thing to do here.
A correct suggestion would be:
```rust
fn_that_actually_does_something(&a, b);
Some(())
```
Somehow the suggestion is not correctly applied to the arguments, when more than one argument is a unit value. I have to look into this a little more, though.
changelog: Fixes suggestion of `unit_arg` lint, so that it suggests semantic equivalent code
Fixes#4741
len_zero: skip ranges if feature `range_is_empty` is not enabled
If the feature is not enabled, calling `is_empty()` on a range is ambiguous. Moreover, the two possible resolutions are unstable methods, one inherent to the range and the other being part of the `ExactSizeIterator` trait.
Since `len_zero` only checks for existing `is_empty()` inherent methods, we only take into account the `range_is_empty` feature.
Related: https://github.com/rust-lang/rust/issues/48111#issuecomment-445132965
changelog: len_zero: avoid linting ranges without #![feature(range_is_empty)]
Fixes: #3807
Extend useless conversion
This PR extends `useless_conversion` lint with `TryFrom` and `TryInto`
fixes: #5344
changelog: Extend `useless_conversion` with `TryFrom` and `TryInto`
Make empty_line_after_outer_attr an early lint
Fixes#5567
Unfortunately I couldn't find a way to reproduce the issue without syn/quote. Considering that most real-world macros use syn and/or quote, I think it's okay to pull them in anyway.
changelog: Fix false positive in [`empty_line_after_outer_attr`]
reversed_empty_ranges: add suggestion for &slice[N..N]
As discussed in the issue thread, the user accepted this solution. Let me know if this is what we want, or if changing the way we lint the N..N case is prefered.
changelog: reversed_empty_ranges: add suggestion for &slice[N..N]
Closes#5628
ptr_arg: honor `allow` attribute on arguments
The `intravisit::Visitor` impl for `LateContextAndPass` only takes into account the attributes of a function parameter inside the `check_param` method. `ptr_arg` starts its heuristics at `check_item` / `check_impl_item` / `check_trait_item`, so the `allow` is not taken into account automatically.
changelog: ptr_arg: honor `allow` attribute on arguments
Fixes#5644
new_without_default: do not suggest deriving
---
changelog: do not suggest deriving `Default` in `new_without_default`
This commit changes the behavior of the `new_without_default` lint to not suggest deriving `Default`. This suggestion is misleading if the `new` implementation does something different than what a derived `Default` implementation would do, because then the two methods would not be equivalent.
Instead, the `can_derive_default` check is removed, and we always suggest implementing `Default` in terms of `new()`.
Clarify the documentation of the `unnecessary_mut_passed` lint
fixes#5433 by replacing "giving" with "passing"
changelog: Clarifies documentation for `unnecessary_mut_passed`
Add to the list of words clippy::doc_markdown ignores
"TypeScript" is the only one of these I actually ran into organically; I can remove the others if they're too much.
changelog: Add to the list of words `clippy::doc_markdown` ignores
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`
Merge some lints together
This PR merges following lints:
- `block_in_if_condition_expr` and `block_in_if_condition_stmt` → `blocks_in_if_conditions`
- `option_map_unwrap_or`, `option_map_unwrap_or_else` and `result_map_unwrap_or_else` → `map_unwrap`
- `option_unwrap_used` and `result_unwrap_used` → `unwrap_used`
- `option_expect_used` and `result_expect_used` → `expect_used`
- `wrong_pub_self_convention` into `wrong_self_convention`
- `for_loop_over_option` and `for_loop_over_result` → `for_loops_over_fallibles`
Lints that have already been merged since the issue was created:
- [x] `new_without_default` and `new_without_default_derive` → `new_without_default`
Need more discussion:
- `string_add` and `string_add_assign`: do we agree to merge them or not? Is there something more to do? → **not merge finally**
- `identity_op` and `modulo_one` → `useless_arithmetic`: seems outdated, since `modulo_arithmetic` has been created.
fixes#1078
changelog: Merging some lints together:
- `block_in_if_condition_expr` and `block_in_if_condition_stmt` → `blocks_in_if_conditions`
- `option_map_unwrap_or`, `option_map_unwrap_or_else` and `result_map_unwrap_or_else` → `map_unwrap_or`
- `option_unwrap_used` and `result_unwrap_used` → `unwrap_used`
- `option_expect_used` and `result_expect_used` → `expect_used`
- `for_loop_over_option` and `for_loop_over_result` → `for_loops_over_fallibles`
Literal error reporting cleanup
While doing some performance work, I noticed some code duplication in `librustc_parser/lexer/mod.rs`, so I cleaned it up.
This PR is probably best reviewed commit by commit.
I'm not sure what the API stability practices for `librustc_lexer` are. Four public methods in `unescape.rs` can be removed, but two are used by clippy, so I left them in for now.
I could open a PR for Rust-Analyzer when this one lands.
But how do I open a PR for clippy? (Git submodules are frustrating to work with)
identity_op: allow `1 << 0`
I went for accepting `1 << 0` verbatim instead of something more general as it seems to be what everyone in the issue thread needed.
changelog: identity_op: allow `1 << 0` as it's a common pattern in bit manipulation code.
Fixes#3430
Downgrade useless_let_if_seq to nursery
I feel that this lint has the wrong balance of incorrect suggestions for a default-enabled lint.
The immediate code I faced was something like:
```rust
fn main() {
let mut good = do1();
if !do2() {
good = false;
}
if good {
println!("good");
}
}
fn do1() -> bool { println!("1"); false }
fn do2() -> bool { println!("2"); false }
```
On this code Clippy calls it unidiomatic and suggests the following diff, which has different behavior in a way that I don't necessarily want.
```diff
- let mut good = do1();
- if !do2() {
- good = false;
- }
+ let good = if !do2() {
+ false
+ } else {
+ do1()
+ };
```
On exploring issues filed about this lint, I have found that other users have also struggled with inappropriate suggestions (https://github.com/rust-lang/rust-clippy/issues/4124, https://github.com/rust-lang/rust-clippy/issues/3043, https://github.com/rust-lang/rust-clippy/issues/2918, https://github.com/rust-lang/rust-clippy/issues/2176) and suggestions that make the code worse (https://github.com/rust-lang/rust-clippy/issues/3769, https://github.com/rust-lang/rust-clippy/issues/2749). Overall I believe that this lint is still at nursery quality for now and should not be enabled.
---
changelog: Remove useless_let_if_seq from default set of enabled lints
Reversed empty ranges
This lint checks range expressions with inverted limits which result in empty ranges. This includes also the ranges used to index slices.
The lint reverse_range_loop was covering iteration of reversed ranges in a for loop, which is a subset of what this new lint covers, so it has been removed. I'm not sure if that's the best choice. It would be doable to check in the new lint that we are not in the arguments of a for loop; I went for removing it because the logic was too similar to keep them separated.
changelog: Added reversed_empty_ranges lint that checks for ranges where the limits have been inverted, resulting in empty ranges. Removed reverse_range_loop which was covering a subset of the new lint.
Closes#4192Closes#96
