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rust-clippy/clippy_lints/src/methods/mod.rs
bors 679fa9f2bf Auto merge of #9187 - sgued:iter-once, r=flip1995 
Add lint recommending using `std::iter::once` and `std::iter::empty`

```
changelog: [`iter_once`]: add new lint
changelog: [`iter_empty`]: add new lint
```

fixes #9186

- \[ ] Followed [lint naming conventions][lint_naming]
- \[x] Added passing UI tests (including committed `.stderr` file)
- \[x] `cargo test` passes locally
- \[x] Executed `cargo dev update_lints`
- \[x] Added lint documentation
- \[x] Run `cargo dev fmt`

[lint_naming]: https://rust-lang.github.io/rfcs/0344-conventions-galore.html#lints

The lint doesn't really follow the naming conventions. I don't have any better idea so I'm open to suggestions.
2022-08-14 15:45:17 +00:00

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mod bind_instead_of_map;
mod bytes_nth;
mod chars_cmp;
mod chars_cmp_with_unwrap;
mod chars_last_cmp;
mod chars_last_cmp_with_unwrap;
mod chars_next_cmp;
mod chars_next_cmp_with_unwrap;
mod clone_on_copy;
mod clone_on_ref_ptr;
mod cloned_instead_of_copied;
mod err_expect;
mod expect_fun_call;
mod expect_used;
mod extend_with_drain;
mod filetype_is_file;
mod filter_map;
mod filter_map_identity;
mod filter_map_next;
mod filter_next;
mod flat_map_identity;
mod flat_map_option;
mod from_iter_instead_of_collect;
mod get_last_with_len;
mod get_unwrap;
mod implicit_clone;
mod inefficient_to_string;
mod inspect_for_each;
mod into_iter_on_ref;
mod is_digit_ascii_radix;
mod iter_cloned_collect;
mod iter_count;
mod iter_next_slice;
mod iter_nth;
mod iter_nth_zero;
mod iter_on_single_or_empty_collections;
mod iter_overeager_cloned;
mod iter_skip_next;
mod iter_with_drain;
mod iterator_step_by_zero;
mod manual_saturating_arithmetic;
mod manual_str_repeat;
mod map_collect_result_unit;
mod map_flatten;
mod map_identity;
mod map_unwrap_or;
mod needless_option_as_deref;
mod needless_option_take;
mod no_effect_replace;
mod obfuscated_if_else;
mod ok_expect;
mod option_as_ref_deref;
mod option_map_or_none;
mod option_map_unwrap_or;
mod or_fun_call;
mod or_then_unwrap;
mod search_is_some;
mod single_char_add_str;
mod single_char_insert_string;
mod single_char_pattern;
mod single_char_push_string;
mod skip_while_next;
mod str_splitn;
mod string_extend_chars;
mod suspicious_map;
mod suspicious_splitn;
mod uninit_assumed_init;
mod unnecessary_filter_map;
mod unnecessary_fold;
mod unnecessary_iter_cloned;
mod unnecessary_join;
mod unnecessary_lazy_eval;
mod unnecessary_to_owned;
mod unwrap_or_else_default;
mod unwrap_used;
mod useless_asref;
mod utils;
mod wrong_self_convention;
mod zst_offset;
use bind_instead_of_map::BindInsteadOfMap;
use clippy_utils::consts::{constant, Constant};
use clippy_utils::diagnostics::{span_lint, span_lint_and_help};
use clippy_utils::ty::{contains_adt_constructor, contains_ty, implements_trait, is_copy, is_type_diagnostic_item};
use clippy_utils::{contains_return, get_trait_def_id, iter_input_pats, meets_msrv, msrvs, paths, return_ty};
use if_chain::if_chain;
use rustc_hir as hir;
use rustc_hir::def::Res;
use rustc_hir::{Expr, ExprKind, PrimTy, QPath, TraitItem, TraitItemKind};
use rustc_lint::{LateContext, LateLintPass, LintContext};
use rustc_middle::lint::in_external_macro;
use rustc_middle::ty::{self, TraitRef, Ty};
use rustc_semver::RustcVersion;
use rustc_session::{declare_tool_lint, impl_lint_pass};
use rustc_span::{sym, Span};
use rustc_typeck::hir_ty_to_ty;
declare_clippy_lint! {
/// ### What it does
/// Checks for usages of `cloned()` on an `Iterator` or `Option` where
/// `copied()` could be used instead.
///
/// ### Why is this bad?
/// `copied()` is better because it guarantees that the type being cloned
/// implements `Copy`.
///
/// ### Example
/// ```rust
/// [1, 2, 3].iter().cloned();
/// ```
/// Use instead:
/// ```rust
/// [1, 2, 3].iter().copied();
/// ```
#[clippy::version = "1.53.0"]
pub CLONED_INSTEAD_OF_COPIED,
pedantic,
"used `cloned` where `copied` could be used instead"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for usage of `_.cloned().<func>()` where call to `.cloned()` can be postponed.
///
/// ### Why is this bad?
/// It's often inefficient to clone all elements of an iterator, when eventually, only some
/// of them will be consumed.
///
/// ### Known Problems
/// This `lint` removes the side of effect of cloning items in the iterator.
/// A code that relies on that side-effect could fail.
///
/// ### Examples
/// ```rust
/// # let vec = vec!["string".to_string()];
/// vec.iter().cloned().take(10);
/// vec.iter().cloned().last();
/// ```
///
/// Use instead:
/// ```rust
/// # let vec = vec!["string".to_string()];
/// vec.iter().take(10).cloned();
/// vec.iter().last().cloned();
/// ```
#[clippy::version = "1.60.0"]
pub ITER_OVEREAGER_CLONED,
perf,
"using `cloned()` early with `Iterator::iter()` can lead to some performance inefficiencies"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for usages of `Iterator::flat_map()` where `filter_map()` could be
/// used instead.
///
/// ### Why is this bad?
/// When applicable, `filter_map()` is more clear since it shows that
/// `Option` is used to produce 0 or 1 items.
///
/// ### Example
/// ```rust
/// let nums: Vec<i32> = ["1", "2", "whee!"].iter().flat_map(|x| x.parse().ok()).collect();
/// ```
/// Use instead:
/// ```rust
/// let nums: Vec<i32> = ["1", "2", "whee!"].iter().filter_map(|x| x.parse().ok()).collect();
/// ```
#[clippy::version = "1.53.0"]
pub FLAT_MAP_OPTION,
pedantic,
"used `flat_map` where `filter_map` could be used instead"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for `.unwrap()` calls on `Option`s and on `Result`s.
///
/// ### Why is this bad?
/// It is better to handle the `None` or `Err` case,
/// or at least call `.expect(_)` with a more helpful message. Still, for a lot of
/// quick-and-dirty code, `unwrap` is a good choice, which is why this lint is
/// `Allow` by default.
///
/// `result.unwrap()` will let the thread panic on `Err` values.
/// Normally, you want to implement more sophisticated error handling,
/// and propagate errors upwards with `?` operator.
///
/// Even if you want to panic on errors, not all `Error`s implement good
/// messages on display. Therefore, it may be beneficial to look at the places
/// where they may get displayed. Activate this lint to do just that.
///
/// ### Examples
/// ```rust
/// # let option = Some(1);
/// # let result: Result<usize, ()> = Ok(1);
/// option.unwrap();
/// result.unwrap();
/// ```
///
/// Use instead:
/// ```rust
/// # let option = Some(1);
/// # let result: Result<usize, ()> = Ok(1);
/// option.expect("more helpful message");
/// result.expect("more helpful message");
/// ```
///
/// If [expect_used](#expect_used) is enabled, instead:
/// ```rust,ignore
/// # let option = Some(1);
/// # let result: Result<usize, ()> = Ok(1);
/// option?;
///
/// // or
///
/// result?;
/// ```
#[clippy::version = "1.45.0"]
pub UNWRAP_USED,
restriction,
"using `.unwrap()` on `Result` or `Option`, which should at least get a better message using `expect()`"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for `.expect()` calls on `Option`s and `Result`s.
///
/// ### Why is this bad?
/// Usually it is better to handle the `None` or `Err` case.
/// Still, for a lot of quick-and-dirty code, `expect` is a good choice, which is why
/// this lint is `Allow` by default.
///
/// `result.expect()` will let the thread panic on `Err`
/// values. Normally, you want to implement more sophisticated error handling,
/// and propagate errors upwards with `?` operator.
///
/// ### Examples
/// ```rust,ignore
/// # let option = Some(1);
/// # let result: Result<usize, ()> = Ok(1);
/// option.expect("one");
/// result.expect("one");
/// ```
///
/// Use instead:
/// ```rust,ignore
/// # let option = Some(1);
/// # let result: Result<usize, ()> = Ok(1);
/// option?;
///
/// // or
///
/// result?;
/// ```
#[clippy::version = "1.45.0"]
pub EXPECT_USED,
restriction,
"using `.expect()` on `Result` or `Option`, which might be better handled"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for methods that should live in a trait
/// implementation of a `std` trait (see [llogiq's blog
/// post](http://llogiq.github.io/2015/07/30/traits.html) for further
/// information) instead of an inherent implementation.
///
/// ### Why is this bad?
/// Implementing the traits improve ergonomics for users of
/// the code, often with very little cost. Also people seeing a `mul(...)`
/// method
/// may expect `*` to work equally, so you should have good reason to disappoint
/// them.
///
/// ### Example
/// ```rust
/// struct X;
/// impl X {
/// fn add(&self, other: &X) -> X {
/// // ..
/// # X
/// }
/// }
/// ```
#[clippy::version = "pre 1.29.0"]
pub SHOULD_IMPLEMENT_TRAIT,
style,
"defining a method that should be implementing a std trait"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for methods with certain name prefixes and which
/// doesn't match how self is taken. The actual rules are:
///
/// |Prefix |Postfix |`self` taken | `self` type |
/// |-------|------------|-------------------------------|--------------|
/// |`as_` | none |`&self` or `&mut self` | any |
/// |`from_`| none | none | any |
/// |`into_`| none |`self` | any |
/// |`is_` | none |`&mut self` or `&self` or none | any |
/// |`to_` | `_mut` |`&mut self` | any |
/// |`to_` | not `_mut` |`self` | `Copy` |
/// |`to_` | not `_mut` |`&self` | not `Copy` |
///
/// Note: Clippy doesn't trigger methods with `to_` prefix in:
/// - Traits definition.
/// Clippy can not tell if a type that implements a trait is `Copy` or not.
/// - Traits implementation, when `&self` is taken.
/// The method signature is controlled by the trait and often `&self` is required for all types that implement the trait
/// (see e.g. the `std::string::ToString` trait).
///
/// Clippy allows `Pin<&Self>` and `Pin<&mut Self>` if `&self` and `&mut self` is required.
///
/// Please find more info here:
/// https://rust-lang.github.io/api-guidelines/naming.html#ad-hoc-conversions-follow-as_-to_-into_-conventions-c-conv
///
/// ### Why is this bad?
/// Consistency breeds readability. If you follow the
/// conventions, your users won't be surprised that they, e.g., need to supply a
/// mutable reference to a `as_..` function.
///
/// ### Example
/// ```rust
/// # struct X;
/// impl X {
/// fn as_str(self) -> &'static str {
/// // ..
/// # ""
/// }
/// }
/// ```
#[clippy::version = "pre 1.29.0"]
pub WRONG_SELF_CONVENTION,
style,
"defining a method named with an established prefix (like \"into_\") that takes `self` with the wrong convention"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for usage of `ok().expect(..)`.
///
/// ### Why is this bad?
/// Because you usually call `expect()` on the `Result`
/// directly to get a better error message.
///
/// ### Known problems
/// The error type needs to implement `Debug`
///
/// ### Example
/// ```rust
/// # let x = Ok::<_, ()>(());
/// x.ok().expect("why did I do this again?");
/// ```
///
/// Use instead:
/// ```rust
/// # let x = Ok::<_, ()>(());
/// x.expect("why did I do this again?");
/// ```
#[clippy::version = "pre 1.29.0"]
pub OK_EXPECT,
style,
"using `ok().expect()`, which gives worse error messages than calling `expect` directly on the Result"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for `.err().expect()` calls on the `Result` type.
///
/// ### Why is this bad?
/// `.expect_err()` can be called directly to avoid the extra type conversion from `err()`.
///
/// ### Example
/// ```should_panic
/// let x: Result<u32, &str> = Ok(10);
/// x.err().expect("Testing err().expect()");
/// ```
/// Use instead:
/// ```should_panic
/// let x: Result<u32, &str> = Ok(10);
/// x.expect_err("Testing expect_err");
/// ```
#[clippy::version = "1.62.0"]
pub ERR_EXPECT,
style,
r#"using `.err().expect("")` when `.expect_err("")` can be used"#
}
declare_clippy_lint! {
/// ### What it does
/// Checks for usages of `_.unwrap_or_else(Default::default)` on `Option` and
/// `Result` values.
///
/// ### Why is this bad?
/// Readability, these can be written as `_.unwrap_or_default`, which is
/// simpler and more concise.
///
/// ### Examples
/// ```rust
/// # let x = Some(1);
/// x.unwrap_or_else(Default::default);
/// x.unwrap_or_else(u32::default);
/// ```
///
/// Use instead:
/// ```rust
/// # let x = Some(1);
/// x.unwrap_or_default();
/// ```
#[clippy::version = "1.56.0"]
pub UNWRAP_OR_ELSE_DEFAULT,
style,
"using `.unwrap_or_else(Default::default)`, which is more succinctly expressed as `.unwrap_or_default()`"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for usage of `option.map(_).unwrap_or(_)` or `option.map(_).unwrap_or_else(_)` or
/// `result.map(_).unwrap_or_else(_)`.
///
/// ### Why is this bad?
/// Readability, these can be written more concisely (resp.) as
/// `option.map_or(_, _)`, `option.map_or_else(_, _)` and `result.map_or_else(_, _)`.
///
/// ### Known problems
/// The order of the arguments is not in execution order
///
/// ### Examples
/// ```rust
/// # let option = Some(1);
/// # let result: Result<usize, ()> = Ok(1);
/// # fn some_function(foo: ()) -> usize { 1 }
/// option.map(|a| a + 1).unwrap_or(0);
/// result.map(|a| a + 1).unwrap_or_else(some_function);
/// ```
///
/// Use instead:
/// ```rust
/// # let option = Some(1);
/// # let result: Result<usize, ()> = Ok(1);
/// # fn some_function(foo: ()) -> usize { 1 }
/// option.map_or(0, |a| a + 1);
/// result.map_or_else(some_function, |a| a + 1);
/// ```
#[clippy::version = "1.45.0"]
pub MAP_UNWRAP_OR,
pedantic,
"using `.map(f).unwrap_or(a)` or `.map(f).unwrap_or_else(func)`, which are more succinctly expressed as `map_or(a, f)` or `map_or_else(a, f)`"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for usage of `_.map_or(None, _)`.
///
/// ### Why is this bad?
/// Readability, this can be written more concisely as
/// `_.and_then(_)`.
///
/// ### Known problems
/// The order of the arguments is not in execution order.
///
/// ### Example
/// ```rust
/// # let opt = Some(1);
/// opt.map_or(None, |a| Some(a + 1));
/// ```
///
/// Use instead:
/// ```rust
/// # let opt = Some(1);
/// opt.and_then(|a| Some(a + 1));
/// ```
#[clippy::version = "pre 1.29.0"]
pub OPTION_MAP_OR_NONE,
style,
"using `Option.map_or(None, f)`, which is more succinctly expressed as `and_then(f)`"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for usage of `_.map_or(None, Some)`.
///
/// ### Why is this bad?
/// Readability, this can be written more concisely as
/// `_.ok()`.
///
/// ### Example
/// ```rust
/// # let r: Result<u32, &str> = Ok(1);
/// assert_eq!(Some(1), r.map_or(None, Some));
/// ```
///
/// Use instead:
/// ```rust
/// # let r: Result<u32, &str> = Ok(1);
/// assert_eq!(Some(1), r.ok());
/// ```
#[clippy::version = "1.44.0"]
pub RESULT_MAP_OR_INTO_OPTION,
style,
"using `Result.map_or(None, Some)`, which is more succinctly expressed as `ok()`"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for usage of `_.and_then(|x| Some(y))`, `_.and_then(|x| Ok(y))` or
/// `_.or_else(|x| Err(y))`.
///
/// ### Why is this bad?
/// Readability, this can be written more concisely as
/// `_.map(|x| y)` or `_.map_err(|x| y)`.
///
/// ### Example
/// ```rust
/// # fn opt() -> Option<&'static str> { Some("42") }
/// # fn res() -> Result<&'static str, &'static str> { Ok("42") }
/// let _ = opt().and_then(|s| Some(s.len()));
/// let _ = res().and_then(|s| if s.len() == 42 { Ok(10) } else { Ok(20) });
/// let _ = res().or_else(|s| if s.len() == 42 { Err(10) } else { Err(20) });
/// ```
///
/// The correct use would be:
///
/// ```rust
/// # fn opt() -> Option<&'static str> { Some("42") }
/// # fn res() -> Result<&'static str, &'static str> { Ok("42") }
/// let _ = opt().map(|s| s.len());
/// let _ = res().map(|s| if s.len() == 42 { 10 } else { 20 });
/// let _ = res().map_err(|s| if s.len() == 42 { 10 } else { 20 });
/// ```
#[clippy::version = "1.45.0"]
pub BIND_INSTEAD_OF_MAP,
complexity,
"using `Option.and_then(|x| Some(y))`, which is more succinctly expressed as `map(|x| y)`"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for usage of `_.filter(_).next()`.
///
/// ### Why is this bad?
/// Readability, this can be written more concisely as
/// `_.find(_)`.
///
/// ### Example
/// ```rust
/// # let vec = vec![1];
/// vec.iter().filter(|x| **x == 0).next();
/// ```
///
/// Use instead:
/// ```rust
/// # let vec = vec![1];
/// vec.iter().find(|x| **x == 0);
/// ```
#[clippy::version = "pre 1.29.0"]
pub FILTER_NEXT,
complexity,
"using `filter(p).next()`, which is more succinctly expressed as `.find(p)`"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for usage of `_.skip_while(condition).next()`.
///
/// ### Why is this bad?
/// Readability, this can be written more concisely as
/// `_.find(!condition)`.
///
/// ### Example
/// ```rust
/// # let vec = vec![1];
/// vec.iter().skip_while(|x| **x == 0).next();
/// ```
///
/// Use instead:
/// ```rust
/// # let vec = vec![1];
/// vec.iter().find(|x| **x != 0);
/// ```
#[clippy::version = "1.42.0"]
pub SKIP_WHILE_NEXT,
complexity,
"using `skip_while(p).next()`, which is more succinctly expressed as `.find(!p)`"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for usage of `_.map(_).flatten(_)` on `Iterator` and `Option`
///
/// ### Why is this bad?
/// Readability, this can be written more concisely as
/// `_.flat_map(_)` for `Iterator` or `_.and_then(_)` for `Option`
///
/// ### Example
/// ```rust
/// let vec = vec![vec![1]];
/// let opt = Some(5);
///
/// vec.iter().map(|x| x.iter()).flatten();
/// opt.map(|x| Some(x * 2)).flatten();
/// ```
///
/// Use instead:
/// ```rust
/// # let vec = vec![vec![1]];
/// # let opt = Some(5);
/// vec.iter().flat_map(|x| x.iter());
/// opt.and_then(|x| Some(x * 2));
/// ```
#[clippy::version = "1.31.0"]
pub MAP_FLATTEN,
complexity,
"using combinations of `flatten` and `map` which can usually be written as a single method call"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for usage of `_.filter(_).map(_)` that can be written more simply
/// as `filter_map(_)`.
///
/// ### Why is this bad?
/// Redundant code in the `filter` and `map` operations is poor style and
/// less performant.
///
/// ### Example
/// ```rust
/// # #![allow(unused)]
/// (0_i32..10)
/// .filter(|n| n.checked_add(1).is_some())
/// .map(|n| n.checked_add(1).unwrap());
/// ```
///
/// Use instead:
/// ```rust
/// # #[allow(unused)]
/// (0_i32..10).filter_map(|n| n.checked_add(1));
/// ```
#[clippy::version = "1.51.0"]
pub MANUAL_FILTER_MAP,
complexity,
"using `_.filter(_).map(_)` in a way that can be written more simply as `filter_map(_)`"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for usage of `_.find(_).map(_)` that can be written more simply
/// as `find_map(_)`.
///
/// ### Why is this bad?
/// Redundant code in the `find` and `map` operations is poor style and
/// less performant.
///
/// ### Example
/// ```rust
/// (0_i32..10)
/// .find(|n| n.checked_add(1).is_some())
/// .map(|n| n.checked_add(1).unwrap());
/// ```
///
/// Use instead:
/// ```rust
/// (0_i32..10).find_map(|n| n.checked_add(1));
/// ```
#[clippy::version = "1.51.0"]
pub MANUAL_FIND_MAP,
complexity,
"using `_.find(_).map(_)` in a way that can be written more simply as `find_map(_)`"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for usage of `_.filter_map(_).next()`.
///
/// ### Why is this bad?
/// Readability, this can be written more concisely as
/// `_.find_map(_)`.
///
/// ### Example
/// ```rust
/// (0..3).filter_map(|x| if x == 2 { Some(x) } else { None }).next();
/// ```
/// Can be written as
///
/// ```rust
/// (0..3).find_map(|x| if x == 2 { Some(x) } else { None });
/// ```
#[clippy::version = "1.36.0"]
pub FILTER_MAP_NEXT,
pedantic,
"using combination of `filter_map` and `next` which can usually be written as a single method call"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for usage of `flat_map(|x| x)`.
///
/// ### Why is this bad?
/// Readability, this can be written more concisely by using `flatten`.
///
/// ### Example
/// ```rust
/// # let iter = vec![vec![0]].into_iter();
/// iter.flat_map(|x| x);
/// ```
/// Can be written as
/// ```rust
/// # let iter = vec![vec![0]].into_iter();
/// iter.flatten();
/// ```
#[clippy::version = "1.39.0"]
pub FLAT_MAP_IDENTITY,
complexity,
"call to `flat_map` where `flatten` is sufficient"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for an iterator or string search (such as `find()`,
/// `position()`, or `rposition()`) followed by a call to `is_some()` or `is_none()`.
///
/// ### Why is this bad?
/// Readability, this can be written more concisely as:
/// * `_.any(_)`, or `_.contains(_)` for `is_some()`,
/// * `!_.any(_)`, or `!_.contains(_)` for `is_none()`.
///
/// ### Example
/// ```rust
/// # #![allow(unused)]
/// let vec = vec![1];
/// vec.iter().find(|x| **x == 0).is_some();
///
/// "hello world".find("world").is_none();
/// ```
///
/// Use instead:
/// ```rust
/// let vec = vec![1];
/// vec.iter().any(|x| *x == 0);
///
/// # #[allow(unused)]
/// !"hello world".contains("world");
/// ```
#[clippy::version = "pre 1.29.0"]
pub SEARCH_IS_SOME,
complexity,
"using an iterator or string search followed by `is_some()` or `is_none()`, which is more succinctly expressed as a call to `any()` or `contains()` (with negation in case of `is_none()`)"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for usage of `.chars().next()` on a `str` to check
/// if it starts with a given char.
///
/// ### Why is this bad?
/// Readability, this can be written more concisely as
/// `_.starts_with(_)`.
///
/// ### Example
/// ```rust
/// let name = "foo";
/// if name.chars().next() == Some('_') {};
/// ```
///
/// Use instead:
/// ```rust
/// let name = "foo";
/// if name.starts_with('_') {};
/// ```
#[clippy::version = "pre 1.29.0"]
pub CHARS_NEXT_CMP,
style,
"using `.chars().next()` to check if a string starts with a char"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for calls to `.or(foo(..))`, `.unwrap_or(foo(..))`,
/// etc., and suggests to use `or_else`, `unwrap_or_else`, etc., or
/// `unwrap_or_default` instead.
///
/// ### Why is this bad?
/// The function will always be called and potentially
/// allocate an object acting as the default.
///
/// ### Known problems
/// If the function has side-effects, not calling it will
/// change the semantic of the program, but you shouldn't rely on that anyway.
///
/// ### Example
/// ```rust
/// # let foo = Some(String::new());
/// foo.unwrap_or(String::new());
/// ```
///
/// Use instead:
/// ```rust
/// # let foo = Some(String::new());
/// foo.unwrap_or_else(String::new);
///
/// // or
///
/// # let foo = Some(String::new());
/// foo.unwrap_or_default();
/// ```
#[clippy::version = "pre 1.29.0"]
pub OR_FUN_CALL,
perf,
"using any `*or` method with a function call, which suggests `*or_else`"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for `.or(…).unwrap()` calls to Options and Results.
///
/// ### Why is this bad?
/// You should use `.unwrap_or(…)` instead for clarity.
///
/// ### Example
/// ```rust
/// # let fallback = "fallback";
/// // Result
/// # type Error = &'static str;
/// # let result: Result<&str, Error> = Err("error");
/// let value = result.or::<Error>(Ok(fallback)).unwrap();
///
/// // Option
/// # let option: Option<&str> = None;
/// let value = option.or(Some(fallback)).unwrap();
/// ```
/// Use instead:
/// ```rust
/// # let fallback = "fallback";
/// // Result
/// # let result: Result<&str, &str> = Err("error");
/// let value = result.unwrap_or(fallback);
///
/// // Option
/// # let option: Option<&str> = None;
/// let value = option.unwrap_or(fallback);
/// ```
#[clippy::version = "1.61.0"]
pub OR_THEN_UNWRAP,
complexity,
"checks for `.or(…).unwrap()` calls to Options and Results."
}
declare_clippy_lint! {
/// ### What it does
/// Checks for calls to `.expect(&format!(...))`, `.expect(foo(..))`,
/// etc., and suggests to use `unwrap_or_else` instead
///
/// ### Why is this bad?
/// The function will always be called.
///
/// ### Known problems
/// If the function has side-effects, not calling it will
/// change the semantics of the program, but you shouldn't rely on that anyway.
///
/// ### Example
/// ```rust
/// # let foo = Some(String::new());
/// # let err_code = "418";
/// # let err_msg = "I'm a teapot";
/// foo.expect(&format!("Err {}: {}", err_code, err_msg));
///
/// // or
///
/// # let foo = Some(String::new());
/// foo.expect(format!("Err {}: {}", err_code, err_msg).as_str());
/// ```
///
/// Use instead:
/// ```rust
/// # let foo = Some(String::new());
/// # let err_code = "418";
/// # let err_msg = "I'm a teapot";
/// foo.unwrap_or_else(|| panic!("Err {}: {}", err_code, err_msg));
/// ```
#[clippy::version = "pre 1.29.0"]
pub EXPECT_FUN_CALL,
perf,
"using any `expect` method with a function call"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for usage of `.clone()` on a `Copy` type.
///
/// ### Why is this bad?
/// The only reason `Copy` types implement `Clone` is for
/// generics, not for using the `clone` method on a concrete type.
///
/// ### Example
/// ```rust
/// 42u64.clone();
/// ```
#[clippy::version = "pre 1.29.0"]
pub CLONE_ON_COPY,
complexity,
"using `clone` on a `Copy` type"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for usage of `.clone()` on a ref-counted pointer,
/// (`Rc`, `Arc`, `rc::Weak`, or `sync::Weak`), and suggests calling Clone via unified
/// function syntax instead (e.g., `Rc::clone(foo)`).
///
/// ### Why is this bad?
/// Calling '.clone()' on an Rc, Arc, or Weak
/// can obscure the fact that only the pointer is being cloned, not the underlying
/// data.
///
/// ### Example
/// ```rust
/// # use std::rc::Rc;
/// let x = Rc::new(1);
///
/// x.clone();
/// ```
///
/// Use instead:
/// ```rust
/// # use std::rc::Rc;
/// # let x = Rc::new(1);
/// Rc::clone(&x);
/// ```
#[clippy::version = "pre 1.29.0"]
pub CLONE_ON_REF_PTR,
restriction,
"using 'clone' on a ref-counted pointer"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for usage of `.clone()` on an `&&T`.
///
/// ### Why is this bad?
/// Cloning an `&&T` copies the inner `&T`, instead of
/// cloning the underlying `T`.
///
/// ### Example
/// ```rust
/// fn main() {
/// let x = vec![1];
/// let y = &&x;
/// let z = y.clone();
/// println!("{:p} {:p}", *y, z); // prints out the same pointer
/// }
/// ```
#[clippy::version = "pre 1.29.0"]
pub CLONE_DOUBLE_REF,
correctness,
"using `clone` on `&&T`"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for usage of `.to_string()` on an `&&T` where
/// `T` implements `ToString` directly (like `&&str` or `&&String`).
///
/// ### Why is this bad?
/// This bypasses the specialized implementation of
/// `ToString` and instead goes through the more expensive string formatting
/// facilities.
///
/// ### Example
/// ```rust
/// // Generic implementation for `T: Display` is used (slow)
/// ["foo", "bar"].iter().map(|s| s.to_string());
///
/// // OK, the specialized impl is used
/// ["foo", "bar"].iter().map(|&s| s.to_string());
/// ```
#[clippy::version = "1.40.0"]
pub INEFFICIENT_TO_STRING,
pedantic,
"using `to_string` on `&&T` where `T: ToString`"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for `new` not returning a type that contains `Self`.
///
/// ### Why is this bad?
/// As a convention, `new` methods are used to make a new
/// instance of a type.
///
/// ### Example
/// In an impl block:
/// ```rust
/// # struct Foo;
/// # struct NotAFoo;
/// impl Foo {
/// fn new() -> NotAFoo {
/// # NotAFoo
/// }
/// }
/// ```
///
/// ```rust
/// # struct Foo;
/// struct Bar(Foo);
/// impl Foo {
/// // Bad. The type name must contain `Self`
/// fn new() -> Bar {
/// # Bar(Foo)
/// }
/// }
/// ```
///
/// ```rust
/// # struct Foo;
/// # struct FooError;
/// impl Foo {
/// // Good. Return type contains `Self`
/// fn new() -> Result<Foo, FooError> {
/// # Ok(Foo)
/// }
/// }
/// ```
///
/// Or in a trait definition:
/// ```rust
/// pub trait Trait {
/// // Bad. The type name must contain `Self`
/// fn new();
/// }
/// ```
///
/// ```rust
/// pub trait Trait {
/// // Good. Return type contains `Self`
/// fn new() -> Self;
/// }
/// ```
#[clippy::version = "pre 1.29.0"]
pub NEW_RET_NO_SELF,
style,
"not returning type containing `Self` in a `new` method"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for string methods that receive a single-character
/// `str` as an argument, e.g., `_.split("x")`.
///
/// ### Why is this bad?
/// Performing these methods using a `char` is faster than
/// using a `str`.
///
/// ### Known problems
/// Does not catch multi-byte unicode characters.
///
/// ### Example
/// ```rust,ignore
/// _.split("x");
/// ```
///
/// Use instead:
/// ```rust,ignore
/// _.split('x');
/// ```
#[clippy::version = "pre 1.29.0"]
pub SINGLE_CHAR_PATTERN,
perf,
"using a single-character str where a char could be used, e.g., `_.split(\"x\")`"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for calling `.step_by(0)` on iterators which panics.
///
/// ### Why is this bad?
/// This very much looks like an oversight. Use `panic!()` instead if you
/// actually intend to panic.
///
/// ### Example
/// ```rust,should_panic
/// for x in (0..100).step_by(0) {
/// //..
/// }
/// ```
#[clippy::version = "pre 1.29.0"]
pub ITERATOR_STEP_BY_ZERO,
correctness,
"using `Iterator::step_by(0)`, which will panic at runtime"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for indirect collection of populated `Option`
///
/// ### Why is this bad?
/// `Option` is like a collection of 0-1 things, so `flatten`
/// automatically does this without suspicious-looking `unwrap` calls.
///
/// ### Example
/// ```rust
/// let _ = std::iter::empty::<Option<i32>>().filter(Option::is_some).map(Option::unwrap);
/// ```
/// Use instead:
/// ```rust
/// let _ = std::iter::empty::<Option<i32>>().flatten();
/// ```
#[clippy::version = "1.53.0"]
pub OPTION_FILTER_MAP,
complexity,
"filtering `Option` for `Some` then force-unwrapping, which can be one type-safe operation"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for the use of `iter.nth(0)`.
///
/// ### Why is this bad?
/// `iter.next()` is equivalent to
/// `iter.nth(0)`, as they both consume the next element,
/// but is more readable.
///
/// ### Example
/// ```rust
/// # use std::collections::HashSet;
/// # let mut s = HashSet::new();
/// # s.insert(1);
/// let x = s.iter().nth(0);
/// ```
///
/// Use instead:
/// ```rust
/// # use std::collections::HashSet;
/// # let mut s = HashSet::new();
/// # s.insert(1);
/// let x = s.iter().next();
/// ```
#[clippy::version = "1.42.0"]
pub ITER_NTH_ZERO,
style,
"replace `iter.nth(0)` with `iter.next()`"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for use of `.iter().nth()` (and the related
/// `.iter_mut().nth()`) on standard library types with *O*(1) element access.
///
/// ### Why is this bad?
/// `.get()` and `.get_mut()` are more efficient and more
/// readable.
///
/// ### Example
/// ```rust
/// let some_vec = vec![0, 1, 2, 3];
/// let bad_vec = some_vec.iter().nth(3);
/// let bad_slice = &some_vec[..].iter().nth(3);
/// ```
/// The correct use would be:
/// ```rust
/// let some_vec = vec![0, 1, 2, 3];
/// let bad_vec = some_vec.get(3);
/// let bad_slice = &some_vec[..].get(3);
/// ```
#[clippy::version = "pre 1.29.0"]
pub ITER_NTH,
perf,
"using `.iter().nth()` on a standard library type with O(1) element access"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for use of `.skip(x).next()` on iterators.
///
/// ### Why is this bad?
/// `.nth(x)` is cleaner
///
/// ### Example
/// ```rust
/// let some_vec = vec![0, 1, 2, 3];
/// let bad_vec = some_vec.iter().skip(3).next();
/// let bad_slice = &some_vec[..].iter().skip(3).next();
/// ```
/// The correct use would be:
/// ```rust
/// let some_vec = vec![0, 1, 2, 3];
/// let bad_vec = some_vec.iter().nth(3);
/// let bad_slice = &some_vec[..].iter().nth(3);
/// ```
#[clippy::version = "pre 1.29.0"]
pub ITER_SKIP_NEXT,
style,
"using `.skip(x).next()` on an iterator"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for use of `.drain(..)` on `Vec` and `VecDeque` for iteration.
///
/// ### Why is this bad?
/// `.into_iter()` is simpler with better performance.
///
/// ### Example
/// ```rust
/// # use std::collections::HashSet;
/// let mut foo = vec![0, 1, 2, 3];
/// let bar: HashSet<usize> = foo.drain(..).collect();
/// ```
/// Use instead:
/// ```rust
/// # use std::collections::HashSet;
/// let foo = vec![0, 1, 2, 3];
/// let bar: HashSet<usize> = foo.into_iter().collect();
/// ```
#[clippy::version = "1.61.0"]
pub ITER_WITH_DRAIN,
nursery,
"replace `.drain(..)` with `.into_iter()`"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for using `x.get(x.len() - 1)` instead of
/// `x.last()`.
///
/// ### Why is this bad?
/// Using `x.last()` is easier to read and has the same
/// result.
///
/// Note that using `x[x.len() - 1]` is semantically different from
/// `x.last()`. Indexing into the array will panic on out-of-bounds
/// accesses, while `x.get()` and `x.last()` will return `None`.
///
/// There is another lint (get_unwrap) that covers the case of using
/// `x.get(index).unwrap()` instead of `x[index]`.
///
/// ### Example
/// ```rust
/// let x = vec![2, 3, 5];
/// let last_element = x.get(x.len() - 1);
/// ```
///
/// Use instead:
/// ```rust
/// let x = vec![2, 3, 5];
/// let last_element = x.last();
/// ```
#[clippy::version = "1.37.0"]
pub GET_LAST_WITH_LEN,
complexity,
"Using `x.get(x.len() - 1)` when `x.last()` is correct and simpler"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for use of `.get().unwrap()` (or
/// `.get_mut().unwrap`) on a standard library type which implements `Index`
///
/// ### Why is this bad?
/// Using the Index trait (`[]`) is more clear and more
/// concise.
///
/// ### Known problems
/// Not a replacement for error handling: Using either
/// `.unwrap()` or the Index trait (`[]`) carries the risk of causing a `panic`
/// if the value being accessed is `None`. If the use of `.get().unwrap()` is a
/// temporary placeholder for dealing with the `Option` type, then this does
/// not mitigate the need for error handling. If there is a chance that `.get()`
/// will be `None` in your program, then it is advisable that the `None` case
/// is handled in a future refactor instead of using `.unwrap()` or the Index
/// trait.
///
/// ### Example
/// ```rust
/// let mut some_vec = vec![0, 1, 2, 3];
/// let last = some_vec.get(3).unwrap();
/// *some_vec.get_mut(0).unwrap() = 1;
/// ```
/// The correct use would be:
/// ```rust
/// let mut some_vec = vec![0, 1, 2, 3];
/// let last = some_vec[3];
/// some_vec[0] = 1;
/// ```
#[clippy::version = "pre 1.29.0"]
pub GET_UNWRAP,
restriction,
"using `.get().unwrap()` or `.get_mut().unwrap()` when using `[]` would work instead"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for occurrences where one vector gets extended instead of append
///
/// ### Why is this bad?
/// Using `append` instead of `extend` is more concise and faster
///
/// ### Example
/// ```rust
/// let mut a = vec![1, 2, 3];
/// let mut b = vec![4, 5, 6];
///
/// a.extend(b.drain(..));
/// ```
///
/// Use instead:
/// ```rust
/// let mut a = vec![1, 2, 3];
/// let mut b = vec![4, 5, 6];
///
/// a.append(&mut b);
/// ```
#[clippy::version = "1.55.0"]
pub EXTEND_WITH_DRAIN,
perf,
"using vec.append(&mut vec) to move the full range of a vector to another"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for the use of `.extend(s.chars())` where s is a
/// `&str` or `String`.
///
/// ### Why is this bad?
/// `.push_str(s)` is clearer
///
/// ### Example
/// ```rust
/// let abc = "abc";
/// let def = String::from("def");
/// let mut s = String::new();
/// s.extend(abc.chars());
/// s.extend(def.chars());
/// ```
/// The correct use would be:
/// ```rust
/// let abc = "abc";
/// let def = String::from("def");
/// let mut s = String::new();
/// s.push_str(abc);
/// s.push_str(&def);
/// ```
#[clippy::version = "pre 1.29.0"]
pub STRING_EXTEND_CHARS,
style,
"using `x.extend(s.chars())` where s is a `&str` or `String`"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for the use of `.cloned().collect()` on slice to
/// create a `Vec`.
///
/// ### Why is this bad?
/// `.to_vec()` is clearer
///
/// ### Example
/// ```rust
/// let s = [1, 2, 3, 4, 5];
/// let s2: Vec<isize> = s[..].iter().cloned().collect();
/// ```
/// The better use would be:
/// ```rust
/// let s = [1, 2, 3, 4, 5];
/// let s2: Vec<isize> = s.to_vec();
/// ```
#[clippy::version = "pre 1.29.0"]
pub ITER_CLONED_COLLECT,
style,
"using `.cloned().collect()` on slice to create a `Vec`"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for usage of `_.chars().last()` or
/// `_.chars().next_back()` on a `str` to check if it ends with a given char.
///
/// ### Why is this bad?
/// Readability, this can be written more concisely as
/// `_.ends_with(_)`.
///
/// ### Example
/// ```rust
/// # let name = "_";
/// name.chars().last() == Some('_') || name.chars().next_back() == Some('-');
/// ```
///
/// Use instead:
/// ```rust
/// # let name = "_";
/// name.ends_with('_') || name.ends_with('-');
/// ```
#[clippy::version = "pre 1.29.0"]
pub CHARS_LAST_CMP,
style,
"using `.chars().last()` or `.chars().next_back()` to check if a string ends with a char"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for usage of `.as_ref()` or `.as_mut()` where the
/// types before and after the call are the same.
///
/// ### Why is this bad?
/// The call is unnecessary.
///
/// ### Example
/// ```rust
/// # fn do_stuff(x: &[i32]) {}
/// let x: &[i32] = &[1, 2, 3, 4, 5];
/// do_stuff(x.as_ref());
/// ```
/// The correct use would be:
/// ```rust
/// # fn do_stuff(x: &[i32]) {}
/// let x: &[i32] = &[1, 2, 3, 4, 5];
/// do_stuff(x);
/// ```
#[clippy::version = "pre 1.29.0"]
pub USELESS_ASREF,
complexity,
"using `as_ref` where the types before and after the call are the same"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for using `fold` when a more succinct alternative exists.
/// Specifically, this checks for `fold`s which could be replaced by `any`, `all`,
/// `sum` or `product`.
///
/// ### Why is this bad?
/// Readability.
///
/// ### Example
/// ```rust
/// # #[allow(unused)]
/// (0..3).fold(false, |acc, x| acc || x > 2);
/// ```
///
/// Use instead:
/// ```rust
/// (0..3).any(|x| x > 2);
/// ```
#[clippy::version = "pre 1.29.0"]
pub UNNECESSARY_FOLD,
style,
"using `fold` when a more succinct alternative exists"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for `filter_map` calls that could be replaced by `filter` or `map`.
/// More specifically it checks if the closure provided is only performing one of the
/// filter or map operations and suggests the appropriate option.
///
/// ### Why is this bad?
/// Complexity. The intent is also clearer if only a single
/// operation is being performed.
///
/// ### Example
/// ```rust
/// let _ = (0..3).filter_map(|x| if x > 2 { Some(x) } else { None });
///
/// // As there is no transformation of the argument this could be written as:
/// let _ = (0..3).filter(|&x| x > 2);
/// ```
///
/// ```rust
/// let _ = (0..4).filter_map(|x| Some(x + 1));
///
/// // As there is no conditional check on the argument this could be written as:
/// let _ = (0..4).map(|x| x + 1);
/// ```
#[clippy::version = "1.31.0"]
pub UNNECESSARY_FILTER_MAP,
complexity,
"using `filter_map` when a more succinct alternative exists"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for `find_map` calls that could be replaced by `find` or `map`. More
/// specifically it checks if the closure provided is only performing one of the
/// find or map operations and suggests the appropriate option.
///
/// ### Why is this bad?
/// Complexity. The intent is also clearer if only a single
/// operation is being performed.
///
/// ### Example
/// ```rust
/// let _ = (0..3).find_map(|x| if x > 2 { Some(x) } else { None });
///
/// // As there is no transformation of the argument this could be written as:
/// let _ = (0..3).find(|&x| x > 2);
/// ```
///
/// ```rust
/// let _ = (0..4).find_map(|x| Some(x + 1));
///
/// // As there is no conditional check on the argument this could be written as:
/// let _ = (0..4).map(|x| x + 1).next();
/// ```
#[clippy::version = "1.61.0"]
pub UNNECESSARY_FIND_MAP,
complexity,
"using `find_map` when a more succinct alternative exists"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for `into_iter` calls on references which should be replaced by `iter`
/// or `iter_mut`.
///
/// ### Why is this bad?
/// Readability. Calling `into_iter` on a reference will not move out its
/// content into the resulting iterator, which is confusing. It is better just call `iter` or
/// `iter_mut` directly.
///
/// ### Example
/// ```rust
/// # let vec = vec![3, 4, 5];
/// (&vec).into_iter();
/// ```
///
/// Use instead:
/// ```rust
/// # let vec = vec![3, 4, 5];
/// (&vec).iter();
/// ```
#[clippy::version = "1.32.0"]
pub INTO_ITER_ON_REF,
style,
"using `.into_iter()` on a reference"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for calls to `map` followed by a `count`.
///
/// ### Why is this bad?
/// It looks suspicious. Maybe `map` was confused with `filter`.
/// If the `map` call is intentional, this should be rewritten
/// using `inspect`. Or, if you intend to drive the iterator to
/// completion, you can just use `for_each` instead.
///
/// ### Example
/// ```rust
/// let _ = (0..3).map(|x| x + 2).count();
/// ```
#[clippy::version = "1.39.0"]
pub SUSPICIOUS_MAP,
suspicious,
"suspicious usage of map"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for `MaybeUninit::uninit().assume_init()`.
///
/// ### Why is this bad?
/// For most types, this is undefined behavior.
///
/// ### Known problems
/// For now, we accept empty tuples and tuples / arrays
/// of `MaybeUninit`. There may be other types that allow uninitialized
/// data, but those are not yet rigorously defined.
///
/// ### Example
/// ```rust
/// // Beware the UB
/// use std::mem::MaybeUninit;
///
/// let _: usize = unsafe { MaybeUninit::uninit().assume_init() };
/// ```
///
/// Note that the following is OK:
///
/// ```rust
/// use std::mem::MaybeUninit;
///
/// let _: [MaybeUninit<bool>; 5] = unsafe {
/// MaybeUninit::uninit().assume_init()
/// };
/// ```
#[clippy::version = "1.39.0"]
pub UNINIT_ASSUMED_INIT,
correctness,
"`MaybeUninit::uninit().assume_init()`"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for `.checked_add/sub(x).unwrap_or(MAX/MIN)`.
///
/// ### Why is this bad?
/// These can be written simply with `saturating_add/sub` methods.
///
/// ### Example
/// ```rust
/// # let y: u32 = 0;
/// # let x: u32 = 100;
/// let add = x.checked_add(y).unwrap_or(u32::MAX);
/// let sub = x.checked_sub(y).unwrap_or(u32::MIN);
/// ```
///
/// can be written using dedicated methods for saturating addition/subtraction as:
///
/// ```rust
/// # let y: u32 = 0;
/// # let x: u32 = 100;
/// let add = x.saturating_add(y);
/// let sub = x.saturating_sub(y);
/// ```
#[clippy::version = "1.39.0"]
pub MANUAL_SATURATING_ARITHMETIC,
style,
"`.checked_add/sub(x).unwrap_or(MAX/MIN)`"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for `offset(_)`, `wrapping_`{`add`, `sub`}, etc. on raw pointers to
/// zero-sized types
///
/// ### Why is this bad?
/// This is a no-op, and likely unintended
///
/// ### Example
/// ```rust
/// unsafe { (&() as *const ()).offset(1) };
/// ```
#[clippy::version = "1.41.0"]
pub ZST_OFFSET,
correctness,
"Check for offset calculations on raw pointers to zero-sized types"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for `FileType::is_file()`.
///
/// ### Why is this bad?
/// When people testing a file type with `FileType::is_file`
/// they are testing whether a path is something they can get bytes from. But
/// `is_file` doesn't cover special file types in unix-like systems, and doesn't cover
/// symlink in windows. Using `!FileType::is_dir()` is a better way to that intention.
///
/// ### Example
/// ```rust
/// # || {
/// let metadata = std::fs::metadata("foo.txt")?;
/// let filetype = metadata.file_type();
///
/// if filetype.is_file() {
/// // read file
/// }
/// # Ok::<_, std::io::Error>(())
/// # };
/// ```
///
/// should be written as:
///
/// ```rust
/// # || {
/// let metadata = std::fs::metadata("foo.txt")?;
/// let filetype = metadata.file_type();
///
/// if !filetype.is_dir() {
/// // read file
/// }
/// # Ok::<_, std::io::Error>(())
/// # };
/// ```
#[clippy::version = "1.42.0"]
pub FILETYPE_IS_FILE,
restriction,
"`FileType::is_file` is not recommended to test for readable file type"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for usage of `_.as_ref().map(Deref::deref)` or it's aliases (such as String::as_str).
///
/// ### Why is this bad?
/// Readability, this can be written more concisely as
/// `_.as_deref()`.
///
/// ### Example
/// ```rust
/// # let opt = Some("".to_string());
/// opt.as_ref().map(String::as_str)
/// # ;
/// ```
/// Can be written as
/// ```rust
/// # let opt = Some("".to_string());
/// opt.as_deref()
/// # ;
/// ```
#[clippy::version = "1.42.0"]
pub OPTION_AS_REF_DEREF,
complexity,
"using `as_ref().map(Deref::deref)`, which is more succinctly expressed as `as_deref()`"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for usage of `iter().next()` on a Slice or an Array
///
/// ### Why is this bad?
/// These can be shortened into `.get()`
///
/// ### Example
/// ```rust
/// # let a = [1, 2, 3];
/// # let b = vec![1, 2, 3];
/// a[2..].iter().next();
/// b.iter().next();
/// ```
/// should be written as:
/// ```rust
/// # let a = [1, 2, 3];
/// # let b = vec![1, 2, 3];
/// a.get(2);
/// b.get(0);
/// ```
#[clippy::version = "1.46.0"]
pub ITER_NEXT_SLICE,
style,
"using `.iter().next()` on a sliced array, which can be shortened to just `.get()`"
}
declare_clippy_lint! {
/// ### What it does
/// Warns when using `push_str`/`insert_str` with a single-character string literal
/// where `push`/`insert` with a `char` would work fine.
///
/// ### Why is this bad?
/// It's less clear that we are pushing a single character.
///
/// ### Example
/// ```rust
/// # let mut string = String::new();
/// string.insert_str(0, "R");
/// string.push_str("R");
/// ```
///
/// Use instead:
/// ```rust
/// # let mut string = String::new();
/// string.insert(0, 'R');
/// string.push('R');
/// ```
#[clippy::version = "1.49.0"]
pub SINGLE_CHAR_ADD_STR,
style,
"`push_str()` or `insert_str()` used with a single-character string literal as parameter"
}
declare_clippy_lint! {
/// ### What it does
/// As the counterpart to `or_fun_call`, this lint looks for unnecessary
/// lazily evaluated closures on `Option` and `Result`.
///
/// This lint suggests changing the following functions, when eager evaluation results in
/// simpler code:
/// - `unwrap_or_else` to `unwrap_or`
/// - `and_then` to `and`
/// - `or_else` to `or`
/// - `get_or_insert_with` to `get_or_insert`
/// - `ok_or_else` to `ok_or`
///
/// ### Why is this bad?
/// Using eager evaluation is shorter and simpler in some cases.
///
/// ### Known problems
/// It is possible, but not recommended for `Deref` and `Index` to have
/// side effects. Eagerly evaluating them can change the semantics of the program.
///
/// ### Example
/// ```rust
/// // example code where clippy issues a warning
/// let opt: Option<u32> = None;
///
/// opt.unwrap_or_else(|| 42);
/// ```
/// Use instead:
/// ```rust
/// let opt: Option<u32> = None;
///
/// opt.unwrap_or(42);
/// ```
#[clippy::version = "1.48.0"]
pub UNNECESSARY_LAZY_EVALUATIONS,
style,
"using unnecessary lazy evaluation, which can be replaced with simpler eager evaluation"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for usage of `_.map(_).collect::<Result<(), _>()`.
///
/// ### Why is this bad?
/// Using `try_for_each` instead is more readable and idiomatic.
///
/// ### Example
/// ```rust
/// (0..3).map(|t| Err(t)).collect::<Result<(), _>>();
/// ```
/// Use instead:
/// ```rust
/// (0..3).try_for_each(|t| Err(t));
/// ```
#[clippy::version = "1.49.0"]
pub MAP_COLLECT_RESULT_UNIT,
style,
"using `.map(_).collect::<Result<(),_>()`, which can be replaced with `try_for_each`"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for `from_iter()` function calls on types that implement the `FromIterator`
/// trait.
///
/// ### Why is this bad?
/// It is recommended style to use collect. See
/// [FromIterator documentation](https://doc.rust-lang.org/std/iter/trait.FromIterator.html)
///
/// ### Example
/// ```rust
/// let five_fives = std::iter::repeat(5).take(5);
///
/// let v = Vec::from_iter(five_fives);
///
/// assert_eq!(v, vec![5, 5, 5, 5, 5]);
/// ```
/// Use instead:
/// ```rust
/// let five_fives = std::iter::repeat(5).take(5);
///
/// let v: Vec<i32> = five_fives.collect();
///
/// assert_eq!(v, vec![5, 5, 5, 5, 5]);
/// ```
#[clippy::version = "1.49.0"]
pub FROM_ITER_INSTEAD_OF_COLLECT,
pedantic,
"use `.collect()` instead of `::from_iter()`"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for usage of `inspect().for_each()`.
///
/// ### Why is this bad?
/// It is the same as performing the computation
/// inside `inspect` at the beginning of the closure in `for_each`.
///
/// ### Example
/// ```rust
/// [1,2,3,4,5].iter()
/// .inspect(|&x| println!("inspect the number: {}", x))
/// .for_each(|&x| {
/// assert!(x >= 0);
/// });
/// ```
/// Can be written as
/// ```rust
/// [1,2,3,4,5].iter()
/// .for_each(|&x| {
/// println!("inspect the number: {}", x);
/// assert!(x >= 0);
/// });
/// ```
#[clippy::version = "1.51.0"]
pub INSPECT_FOR_EACH,
complexity,
"using `.inspect().for_each()`, which can be replaced with `.for_each()`"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for usage of `filter_map(|x| x)`.
///
/// ### Why is this bad?
/// Readability, this can be written more concisely by using `flatten`.
///
/// ### Example
/// ```rust
/// # let iter = vec![Some(1)].into_iter();
/// iter.filter_map(|x| x);
/// ```
/// Use instead:
/// ```rust
/// # let iter = vec![Some(1)].into_iter();
/// iter.flatten();
/// ```
#[clippy::version = "1.52.0"]
pub FILTER_MAP_IDENTITY,
complexity,
"call to `filter_map` where `flatten` is sufficient"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for instances of `map(f)` where `f` is the identity function.
///
/// ### Why is this bad?
/// It can be written more concisely without the call to `map`.
///
/// ### Example
/// ```rust
/// let x = [1, 2, 3];
/// let y: Vec<_> = x.iter().map(|x| x).map(|x| 2*x).collect();
/// ```
/// Use instead:
/// ```rust
/// let x = [1, 2, 3];
/// let y: Vec<_> = x.iter().map(|x| 2*x).collect();
/// ```
#[clippy::version = "1.47.0"]
pub MAP_IDENTITY,
complexity,
"using iterator.map(|x| x)"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for the use of `.bytes().nth()`.
///
/// ### Why is this bad?
/// `.as_bytes().get()` is more efficient and more
/// readable.
///
/// ### Example
/// ```rust
/// # #[allow(unused)]
/// "Hello".bytes().nth(3);
/// ```
///
/// Use instead:
/// ```rust
/// # #[allow(unused)]
/// "Hello".as_bytes().get(3);
/// ```
#[clippy::version = "1.52.0"]
pub BYTES_NTH,
style,
"replace `.bytes().nth()` with `.as_bytes().get()`"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for the usage of `_.to_owned()`, `vec.to_vec()`, or similar when calling `_.clone()` would be clearer.
///
/// ### Why is this bad?
/// These methods do the same thing as `_.clone()` but may be confusing as
/// to why we are calling `to_vec` on something that is already a `Vec` or calling `to_owned` on something that is already owned.
///
/// ### Example
/// ```rust
/// let a = vec![1, 2, 3];
/// let b = a.to_vec();
/// let c = a.to_owned();
/// ```
/// Use instead:
/// ```rust
/// let a = vec![1, 2, 3];
/// let b = a.clone();
/// let c = a.clone();
/// ```
#[clippy::version = "1.52.0"]
pub IMPLICIT_CLONE,
pedantic,
"implicitly cloning a value by invoking a function on its dereferenced type"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for the use of `.iter().count()`.
///
/// ### Why is this bad?
/// `.len()` is more efficient and more
/// readable.
///
/// ### Example
/// ```rust
/// # #![allow(unused)]
/// let some_vec = vec![0, 1, 2, 3];
///
/// some_vec.iter().count();
/// &some_vec[..].iter().count();
/// ```
///
/// Use instead:
/// ```rust
/// let some_vec = vec![0, 1, 2, 3];
///
/// some_vec.len();
/// &some_vec[..].len();
/// ```
#[clippy::version = "1.52.0"]
pub ITER_COUNT,
complexity,
"replace `.iter().count()` with `.len()`"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for calls to [`splitn`]
/// (https://doc.rust-lang.org/std/primitive.str.html#method.splitn) and
/// related functions with either zero or one splits.
///
/// ### Why is this bad?
/// These calls don't actually split the value and are
/// likely to be intended as a different number.
///
/// ### Example
/// ```rust
/// # let s = "";
/// for x in s.splitn(1, ":") {
/// // ..
/// }
/// ```
///
/// Use instead:
/// ```rust
/// # let s = "";
/// for x in s.splitn(2, ":") {
/// // ..
/// }
/// ```
#[clippy::version = "1.54.0"]
pub SUSPICIOUS_SPLITN,
correctness,
"checks for `.splitn(0, ..)` and `.splitn(1, ..)`"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for manual implementations of `str::repeat`
///
/// ### Why is this bad?
/// These are both harder to read, as well as less performant.
///
/// ### Example
/// ```rust
/// let x: String = std::iter::repeat('x').take(10).collect();
/// ```
///
/// Use instead:
/// ```rust
/// let x: String = "x".repeat(10);
/// ```
#[clippy::version = "1.54.0"]
pub MANUAL_STR_REPEAT,
perf,
"manual implementation of `str::repeat`"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for usages of `str::splitn(2, _)`
///
/// ### Why is this bad?
/// `split_once` is both clearer in intent and slightly more efficient.
///
/// ### Example
/// ```rust,ignore
/// let s = "key=value=add";
/// let (key, value) = s.splitn(2, '=').next_tuple()?;
/// let value = s.splitn(2, '=').nth(1)?;
///
/// let mut parts = s.splitn(2, '=');
/// let key = parts.next()?;
/// let value = parts.next()?;
/// ```
///
/// Use instead:
/// ```rust,ignore
/// let s = "key=value=add";
/// let (key, value) = s.split_once('=')?;
/// let value = s.split_once('=')?.1;
///
/// let (key, value) = s.split_once('=')?;
/// ```
///
/// ### Limitations
/// The multiple statement variant currently only detects `iter.next()?`/`iter.next().unwrap()`
/// in two separate `let` statements that immediately follow the `splitn()`
#[clippy::version = "1.57.0"]
pub MANUAL_SPLIT_ONCE,
complexity,
"replace `.splitn(2, pat)` with `.split_once(pat)`"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for usages of `str::splitn` (or `str::rsplitn`) where using `str::split` would be the same.
/// ### Why is this bad?
/// The function `split` is simpler and there is no performance difference in these cases, considering
/// that both functions return a lazy iterator.
/// ### Example
/// ```rust
/// let str = "key=value=add";
/// let _ = str.splitn(3, '=').next().unwrap();
/// ```
///
/// Use instead:
/// ```rust
/// let str = "key=value=add";
/// let _ = str.split('=').next().unwrap();
/// ```
#[clippy::version = "1.59.0"]
pub NEEDLESS_SPLITN,
complexity,
"usages of `str::splitn` that can be replaced with `str::split`"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for unnecessary calls to [`ToOwned::to_owned`](https://doc.rust-lang.org/std/borrow/trait.ToOwned.html#tymethod.to_owned)
/// and other `to_owned`-like functions.
///
/// ### Why is this bad?
/// The unnecessary calls result in useless allocations.
///
/// ### Known problems
/// `unnecessary_to_owned` can falsely trigger if `IntoIterator::into_iter` is applied to an
/// owned copy of a resource and the resource is later used mutably. See
/// [#8148](https://github.com/rust-lang/rust-clippy/issues/8148).
///
/// ### Example
/// ```rust
/// let path = std::path::Path::new("x");
/// foo(&path.to_string_lossy().to_string());
/// fn foo(s: &str) {}
/// ```
/// Use instead:
/// ```rust
/// let path = std::path::Path::new("x");
/// foo(&path.to_string_lossy());
/// fn foo(s: &str) {}
/// ```
#[clippy::version = "1.59.0"]
pub UNNECESSARY_TO_OWNED,
perf,
"unnecessary calls to `to_owned`-like functions"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for use of `.collect::<Vec<String>>().join("")` on iterators.
///
/// ### Why is this bad?
/// `.collect::<String>()` is more concise and might be more performant
///
/// ### Example
/// ```rust
/// let vector = vec!["hello", "world"];
/// let output = vector.iter().map(|item| item.to_uppercase()).collect::<Vec<String>>().join("");
/// println!("{}", output);
/// ```
/// The correct use would be:
/// ```rust
/// let vector = vec!["hello", "world"];
/// let output = vector.iter().map(|item| item.to_uppercase()).collect::<String>();
/// println!("{}", output);
/// ```
/// ### Known problems
/// While `.collect::<String>()` is sometimes more performant, there are cases where
/// using `.collect::<String>()` over `.collect::<Vec<String>>().join("")`
/// will prevent loop unrolling and will result in a negative performance impact.
///
/// Additionally, differences have been observed between aarch64 and x86_64 assembly output,
/// with aarch64 tending to producing faster assembly in more cases when using `.collect::<String>()`
#[clippy::version = "1.61.0"]
pub UNNECESSARY_JOIN,
pedantic,
"using `.collect::<Vec<String>>().join(\"\")` on an iterator"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for no-op uses of `Option::{as_deref, as_deref_mut}`,
/// for example, `Option<&T>::as_deref()` returns the same type.
///
/// ### Why is this bad?
/// Redundant code and improving readability.
///
/// ### Example
/// ```rust
/// let a = Some(&1);
/// let b = a.as_deref(); // goes from Option<&i32> to Option<&i32>
/// ```
///
/// Use instead:
/// ```rust
/// let a = Some(&1);
/// let b = a;
/// ```
#[clippy::version = "1.57.0"]
pub NEEDLESS_OPTION_AS_DEREF,
complexity,
"no-op use of `deref` or `deref_mut` method to `Option`."
}
declare_clippy_lint! {
/// ### What it does
/// Finds usages of [`char::is_digit`](https://doc.rust-lang.org/stable/std/primitive.char.html#method.is_digit) that
/// can be replaced with [`is_ascii_digit`](https://doc.rust-lang.org/stable/std/primitive.char.html#method.is_ascii_digit) or
/// [`is_ascii_hexdigit`](https://doc.rust-lang.org/stable/std/primitive.char.html#method.is_ascii_hexdigit).
///
/// ### Why is this bad?
/// `is_digit(..)` is slower and requires specifying the radix.
///
/// ### Example
/// ```rust
/// let c: char = '6';
/// c.is_digit(10);
/// c.is_digit(16);
/// ```
/// Use instead:
/// ```rust
/// let c: char = '6';
/// c.is_ascii_digit();
/// c.is_ascii_hexdigit();
/// ```
#[clippy::version = "1.62.0"]
pub IS_DIGIT_ASCII_RADIX,
style,
"use of `char::is_digit(..)` with literal radix of 10 or 16"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for calling `take` function after `as_ref`.
///
/// ### Why is this bad?
/// Redundant code. `take` writes `None` to its argument.
/// In this case the modification is useless as it's a temporary that cannot be read from afterwards.
///
/// ### Example
/// ```rust
/// let x = Some(3);
/// x.as_ref().take();
/// ```
/// Use instead:
/// ```rust
/// let x = Some(3);
/// x.as_ref();
/// ```
#[clippy::version = "1.62.0"]
pub NEEDLESS_OPTION_TAKE,
complexity,
"using `.as_ref().take()` on a temporary value"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for `replace` statements which have no effect.
///
/// ### Why is this bad?
/// It's either a mistake or confusing.
///
/// ### Example
/// ```rust
/// "1234".replace("12", "12");
/// "1234".replacen("12", "12", 1);
/// ```
#[clippy::version = "1.63.0"]
pub NO_EFFECT_REPLACE,
suspicious,
"replace with no effect"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for usages of `.then_some(..).unwrap_or(..)`
///
/// ### Why is this bad?
/// This can be written more clearly with `if .. else ..`
///
/// ### Limitations
/// This lint currently only looks for usages of
/// `.then_some(..).unwrap_or(..)`, but will be expanded
/// to account for similar patterns.
///
/// ### Example
/// ```rust
/// let x = true;
/// x.then_some("a").unwrap_or("b");
/// ```
/// Use instead:
/// ```rust
/// let x = true;
/// if x { "a" } else { "b" };
/// ```
#[clippy::version = "1.64.0"]
pub OBFUSCATED_IF_ELSE,
style,
"use of `.then_some(..).unwrap_or(..)` can be written \
more clearly with `if .. else ..`"
}
declare_clippy_lint! {
/// ### What it does
///
/// Checks for calls to `iter`, `iter_mut` or `into_iter` on collections containing a single item
///
/// ### Why is this bad?
///
/// It is simpler to use the once function from the standard library:
///
/// ### Example
///
/// ```rust
/// let a = [123].iter();
/// let b = Some(123).into_iter();
/// ```
/// Use instead:
/// ```rust
/// use std::iter;
/// let a = iter::once(&123);
/// let b = iter::once(123);
/// ```
///
/// ### Known problems
///
/// The type of the resulting iterator might become incompatible with its usage
#[clippy::version = "1.64.0"]
pub ITER_ON_SINGLE_ITEMS,
nursery,
"Iterator for array of length 1"
}
declare_clippy_lint! {
/// ### What it does
///
/// Checks for calls to `iter`, `iter_mut` or `into_iter` on empty collections
///
/// ### Why is this bad?
///
/// It is simpler to use the empty function from the standard library:
///
/// ### Example
///
/// ```rust
/// use std::{slice, option};
/// let a: slice::Iter<i32> = [].iter();
/// let f: option::IntoIter<i32> = None.into_iter();
/// ```
/// Use instead:
/// ```rust
/// use std::iter;
/// let a: iter::Empty<i32> = iter::empty();
/// let b: iter::Empty<i32> = iter::empty();
/// ```
///
/// ### Known problems
///
/// The type of the resulting iterator might become incompatible with its usage
#[clippy::version = "1.64.0"]
pub ITER_ON_EMPTY_COLLECTIONS,
nursery,
"Iterator for empty array"
}
pub struct Methods {
avoid_breaking_exported_api: bool,
msrv: Option<RustcVersion>,
allow_expect_in_tests: bool,
allow_unwrap_in_tests: bool,
}
impl Methods {
#[must_use]
pub fn new(
avoid_breaking_exported_api: bool,
msrv: Option<RustcVersion>,
allow_expect_in_tests: bool,
allow_unwrap_in_tests: bool,
) -> Self {
Self {
avoid_breaking_exported_api,
msrv,
allow_expect_in_tests,
allow_unwrap_in_tests,
}
}
}
impl_lint_pass!(Methods => [
UNWRAP_USED,
EXPECT_USED,
SHOULD_IMPLEMENT_TRAIT,
WRONG_SELF_CONVENTION,
OK_EXPECT,
UNWRAP_OR_ELSE_DEFAULT,
MAP_UNWRAP_OR,
RESULT_MAP_OR_INTO_OPTION,
OPTION_MAP_OR_NONE,
BIND_INSTEAD_OF_MAP,
OR_FUN_CALL,
OR_THEN_UNWRAP,
EXPECT_FUN_CALL,
CHARS_NEXT_CMP,
CHARS_LAST_CMP,
CLONE_ON_COPY,
CLONE_ON_REF_PTR,
CLONE_DOUBLE_REF,
ITER_OVEREAGER_CLONED,
CLONED_INSTEAD_OF_COPIED,
FLAT_MAP_OPTION,
INEFFICIENT_TO_STRING,
NEW_RET_NO_SELF,
SINGLE_CHAR_PATTERN,
SINGLE_CHAR_ADD_STR,
SEARCH_IS_SOME,
FILTER_NEXT,
SKIP_WHILE_NEXT,
FILTER_MAP_IDENTITY,
MAP_IDENTITY,
MANUAL_FILTER_MAP,
MANUAL_FIND_MAP,
OPTION_FILTER_MAP,
FILTER_MAP_NEXT,
FLAT_MAP_IDENTITY,
MAP_FLATTEN,
ITERATOR_STEP_BY_ZERO,
ITER_NEXT_SLICE,
ITER_COUNT,
ITER_NTH,
ITER_NTH_ZERO,
BYTES_NTH,
ITER_SKIP_NEXT,
GET_UNWRAP,
GET_LAST_WITH_LEN,
STRING_EXTEND_CHARS,
ITER_CLONED_COLLECT,
ITER_WITH_DRAIN,
USELESS_ASREF,
UNNECESSARY_FOLD,
UNNECESSARY_FILTER_MAP,
UNNECESSARY_FIND_MAP,
INTO_ITER_ON_REF,
SUSPICIOUS_MAP,
UNINIT_ASSUMED_INIT,
MANUAL_SATURATING_ARITHMETIC,
ZST_OFFSET,
FILETYPE_IS_FILE,
OPTION_AS_REF_DEREF,
UNNECESSARY_LAZY_EVALUATIONS,
MAP_COLLECT_RESULT_UNIT,
FROM_ITER_INSTEAD_OF_COLLECT,
INSPECT_FOR_EACH,
IMPLICIT_CLONE,
SUSPICIOUS_SPLITN,
MANUAL_STR_REPEAT,
EXTEND_WITH_DRAIN,
MANUAL_SPLIT_ONCE,
NEEDLESS_SPLITN,
UNNECESSARY_TO_OWNED,
UNNECESSARY_JOIN,
ERR_EXPECT,
NEEDLESS_OPTION_AS_DEREF,
IS_DIGIT_ASCII_RADIX,
NEEDLESS_OPTION_TAKE,
NO_EFFECT_REPLACE,
OBFUSCATED_IF_ELSE,
ITER_ON_SINGLE_ITEMS,
ITER_ON_EMPTY_COLLECTIONS
]);
/// Extracts a method call name, args, and `Span` of the method name.
fn method_call<'tcx>(recv: &'tcx hir::Expr<'tcx>) -> Option<(&'tcx str, &'tcx [hir::Expr<'tcx>], Span)> {
if let ExprKind::MethodCall(path, args, _) = recv.kind {
if !args.iter().any(|e| e.span.from_expansion()) {
let name = path.ident.name.as_str();
return Some((name, args, path.ident.span));
}
}
None
}
impl<'tcx> LateLintPass<'tcx> for Methods {
fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>) {
if expr.span.from_expansion() {
return;
}
self.check_methods(cx, expr);
match expr.kind {
hir::ExprKind::Call(func, args) => {
from_iter_instead_of_collect::check(cx, expr, args, func);
},
hir::ExprKind::MethodCall(method_call, args, _) => {
let method_span = method_call.ident.span;
or_fun_call::check(cx, expr, method_span, method_call.ident.as_str(), args);
expect_fun_call::check(cx, expr, method_span, method_call.ident.as_str(), args);
clone_on_copy::check(cx, expr, method_call.ident.name, args);
clone_on_ref_ptr::check(cx, expr, method_call.ident.name, args);
inefficient_to_string::check(cx, expr, method_call.ident.name, args);
single_char_add_str::check(cx, expr, args);
into_iter_on_ref::check(cx, expr, method_span, method_call.ident.name, args);
single_char_pattern::check(cx, expr, method_call.ident.name, args);
unnecessary_to_owned::check(cx, expr, method_call.ident.name, args, self.msrv);
},
hir::ExprKind::Binary(op, lhs, rhs) if op.node == hir::BinOpKind::Eq || op.node == hir::BinOpKind::Ne => {
let mut info = BinaryExprInfo {
expr,
chain: lhs,
other: rhs,
eq: op.node == hir::BinOpKind::Eq,
};
lint_binary_expr_with_method_call(cx, &mut info);
},
_ => (),
}
}
#[allow(clippy::too_many_lines)]
fn check_impl_item(&mut self, cx: &LateContext<'tcx>, impl_item: &'tcx hir::ImplItem<'_>) {
if in_external_macro(cx.sess(), impl_item.span) {
return;
}
let name = impl_item.ident.name.as_str();
let parent = cx.tcx.hir().get_parent_item(impl_item.hir_id());
let item = cx.tcx.hir().expect_item(parent);
let self_ty = cx.tcx.type_of(item.def_id);
let implements_trait = matches!(item.kind, hir::ItemKind::Impl(hir::Impl { of_trait: Some(_), .. }));
if_chain! {
if let hir::ImplItemKind::Fn(ref sig, id) = impl_item.kind;
if let Some(first_arg) = iter_input_pats(sig.decl, cx.tcx.hir().body(id)).next();
let method_sig = cx.tcx.fn_sig(impl_item.def_id);
let method_sig = cx.tcx.erase_late_bound_regions(method_sig);
let first_arg_ty = method_sig.inputs().iter().next();
// check conventions w.r.t. conversion method names and predicates
if let Some(first_arg_ty) = first_arg_ty;
then {
// if this impl block implements a trait, lint in trait definition instead
if !implements_trait && cx.access_levels.is_exported(impl_item.def_id) {
// check missing trait implementations
for method_config in &TRAIT_METHODS {
if name == method_config.method_name &&
sig.decl.inputs.len() == method_config.param_count &&
method_config.output_type.matches(&sig.decl.output) &&
method_config.self_kind.matches(cx, self_ty, *first_arg_ty) &&
fn_header_equals(method_config.fn_header, sig.header) &&
method_config.lifetime_param_cond(impl_item)
{
span_lint_and_help(
cx,
SHOULD_IMPLEMENT_TRAIT,
impl_item.span,
&format!(
"method `{}` can be confused for the standard trait method `{}::{}`",
method_config.method_name,
method_config.trait_name,
method_config.method_name
),
None,
&format!(
"consider implementing the trait `{}` or choosing a less ambiguous method name",
method_config.trait_name
)
);
}
}
}
if sig.decl.implicit_self.has_implicit_self()
&& !(self.avoid_breaking_exported_api
&& cx.access_levels.is_exported(impl_item.def_id))
{
wrong_self_convention::check(
cx,
name,
self_ty,
*first_arg_ty,
first_arg.pat.span,
implements_trait,
false
);
}
}
}
// if this impl block implements a trait, lint in trait definition instead
if implements_trait {
return;
}
if let hir::ImplItemKind::Fn(_, _) = impl_item.kind {
let ret_ty = return_ty(cx, impl_item.hir_id());
// walk the return type and check for Self (this does not check associated types)
if let Some(self_adt) = self_ty.ty_adt_def() {
if contains_adt_constructor(ret_ty, self_adt) {
return;
}
} else if contains_ty(ret_ty, self_ty) {
return;
}
// if return type is impl trait, check the associated types
if let ty::Opaque(def_id, _) = *ret_ty.kind() {
// one of the associated types must be Self
for &(predicate, _span) in cx.tcx.explicit_item_bounds(def_id) {
if let ty::PredicateKind::Projection(projection_predicate) = predicate.kind().skip_binder() {
let assoc_ty = match projection_predicate.term {
ty::Term::Ty(ty) => ty,
ty::Term::Const(_c) => continue,
};
// walk the associated type and check for Self
if let Some(self_adt) = self_ty.ty_adt_def() {
if contains_adt_constructor(assoc_ty, self_adt) {
return;
}
} else if contains_ty(assoc_ty, self_ty) {
return;
}
}
}
}
if name == "new" && ret_ty != self_ty {
span_lint(
cx,
NEW_RET_NO_SELF,
impl_item.span,
"methods called `new` usually return `Self`",
);
}
}
}
fn check_trait_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx TraitItem<'_>) {
if in_external_macro(cx.tcx.sess, item.span) {
return;
}
if_chain! {
if let TraitItemKind::Fn(ref sig, _) = item.kind;
if sig.decl.implicit_self.has_implicit_self();
if let Some(first_arg_ty) = sig.decl.inputs.iter().next();
then {
let first_arg_span = first_arg_ty.span;
let first_arg_ty = hir_ty_to_ty(cx.tcx, first_arg_ty);
let self_ty = TraitRef::identity(cx.tcx, item.def_id.to_def_id()).self_ty().skip_binder();
wrong_self_convention::check(
cx,
item.ident.name.as_str(),
self_ty,
first_arg_ty,
first_arg_span,
false,
true
);
}
}
if_chain! {
if item.ident.name == sym::new;
if let TraitItemKind::Fn(_, _) = item.kind;
let ret_ty = return_ty(cx, item.hir_id());
let self_ty = TraitRef::identity(cx.tcx, item.def_id.to_def_id()).self_ty().skip_binder();
if !contains_ty(ret_ty, self_ty);
then {
span_lint(
cx,
NEW_RET_NO_SELF,
item.span,
"methods called `new` usually return `Self`",
);
}
}
}
extract_msrv_attr!(LateContext);
}
impl Methods {
#[allow(clippy::too_many_lines)]
fn check_methods<'tcx>(&self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
if let Some((name, [recv, args @ ..], span)) = method_call(expr) {
match (name, args) {
("add" | "offset" | "sub" | "wrapping_offset" | "wrapping_add" | "wrapping_sub", [_arg]) => {
zst_offset::check(cx, expr, recv);
},
("and_then", [arg]) => {
let biom_option_linted = bind_instead_of_map::OptionAndThenSome::check(cx, expr, recv, arg);
let biom_result_linted = bind_instead_of_map::ResultAndThenOk::check(cx, expr, recv, arg);
if !biom_option_linted && !biom_result_linted {
unnecessary_lazy_eval::check(cx, expr, recv, arg, "and");
}
},
("as_deref" | "as_deref_mut", []) => {
needless_option_as_deref::check(cx, expr, recv, name);
},
("as_mut", []) => useless_asref::check(cx, expr, "as_mut", recv),
("as_ref", []) => useless_asref::check(cx, expr, "as_ref", recv),
("assume_init", []) => uninit_assumed_init::check(cx, expr, recv),
("cloned", []) => cloned_instead_of_copied::check(cx, expr, recv, span, self.msrv),
("collect", []) => match method_call(recv) {
Some((name @ ("cloned" | "copied"), [recv2], _)) => {
iter_cloned_collect::check(cx, name, expr, recv2);
},
Some(("map", [m_recv, m_arg], _)) => {
map_collect_result_unit::check(cx, expr, m_recv, m_arg, recv);
},
Some(("take", [take_self_arg, take_arg], _)) => {
if meets_msrv(self.msrv, msrvs::STR_REPEAT) {
manual_str_repeat::check(cx, expr, recv, take_self_arg, take_arg);
}
},
_ => {},
},
("count", []) => match method_call(recv) {
Some(("cloned", [recv2], _)) => iter_overeager_cloned::check(cx, expr, recv, recv2, true, false),
Some((name2 @ ("into_iter" | "iter" | "iter_mut"), [recv2], _)) => {
iter_count::check(cx, expr, recv2, name2);
},
Some(("map", [_, arg], _)) => suspicious_map::check(cx, expr, recv, arg),
_ => {},
},
("drain", [arg]) => {
iter_with_drain::check(cx, expr, recv, span, arg);
},
("expect", [_]) => match method_call(recv) {
Some(("ok", [recv], _)) => ok_expect::check(cx, expr, recv),
Some(("err", [recv], err_span)) => err_expect::check(cx, expr, recv, self.msrv, span, err_span),
_ => expect_used::check(cx, expr, recv, self.allow_expect_in_tests),
},
("extend", [arg]) => {
string_extend_chars::check(cx, expr, recv, arg);
extend_with_drain::check(cx, expr, recv, arg);
},
("filter_map", [arg]) => {
unnecessary_filter_map::check(cx, expr, arg, name);
filter_map_identity::check(cx, expr, arg, span);
},
("find_map", [arg]) => {
unnecessary_filter_map::check(cx, expr, arg, name);
},
("flat_map", [arg]) => {
flat_map_identity::check(cx, expr, arg, span);
flat_map_option::check(cx, expr, arg, span);
},
("flatten", []) => match method_call(recv) {
Some(("map", [recv, map_arg], map_span)) => map_flatten::check(cx, expr, recv, map_arg, map_span),
Some(("cloned", [recv2], _)) => iter_overeager_cloned::check(cx, expr, recv, recv2, false, true),
_ => {},
},
("fold", [init, acc]) => unnecessary_fold::check(cx, expr, init, acc, span),
("for_each", [_]) => {
if let Some(("inspect", [_, _], span2)) = method_call(recv) {
inspect_for_each::check(cx, expr, span2);
}
},
("get", [arg]) => get_last_with_len::check(cx, expr, recv, arg),
("get_or_insert_with", [arg]) => unnecessary_lazy_eval::check(cx, expr, recv, arg, "get_or_insert"),
("is_file", []) => filetype_is_file::check(cx, expr, recv),
("is_digit", [radix]) => is_digit_ascii_radix::check(cx, expr, recv, radix, self.msrv),
("is_none", []) => check_is_some_is_none(cx, expr, recv, false),
("is_some", []) => check_is_some_is_none(cx, expr, recv, true),
("iter" | "iter_mut" | "into_iter", []) => {
iter_on_single_or_empty_collections::check(cx, expr, name, recv);
},
("join", [join_arg]) => {
if let Some(("collect", _, span)) = method_call(recv) {
unnecessary_join::check(cx, expr, recv, join_arg, span);
}
},
("last", []) | ("skip", [_]) => {
if let Some((name2, [recv2, args2 @ ..], _span2)) = method_call(recv) {
if let ("cloned", []) = (name2, args2) {
iter_overeager_cloned::check(cx, expr, recv, recv2, false, false);
}
}
},
(name @ ("map" | "map_err"), [m_arg]) => {
if let Some((name, [recv2, args @ ..], span2)) = method_call(recv) {
match (name, args) {
("as_mut", []) => option_as_ref_deref::check(cx, expr, recv2, m_arg, true, self.msrv),
("as_ref", []) => option_as_ref_deref::check(cx, expr, recv2, m_arg, false, self.msrv),
("filter", [f_arg]) => {
filter_map::check(cx, expr, recv2, f_arg, span2, recv, m_arg, span, false);
},
("find", [f_arg]) => {
filter_map::check(cx, expr, recv2, f_arg, span2, recv, m_arg, span, true);
},
_ => {},
}
}
map_identity::check(cx, expr, recv, m_arg, name, span);
},
("map_or", [def, map]) => option_map_or_none::check(cx, expr, recv, def, map),
("next", []) => {
if let Some((name2, [recv2, args2 @ ..], _)) = method_call(recv) {
match (name2, args2) {
("cloned", []) => iter_overeager_cloned::check(cx, expr, recv, recv2, false, false),
("filter", [arg]) => filter_next::check(cx, expr, recv2, arg),
("filter_map", [arg]) => filter_map_next::check(cx, expr, recv2, arg, self.msrv),
("iter", []) => iter_next_slice::check(cx, expr, recv2),
("skip", [arg]) => iter_skip_next::check(cx, expr, recv2, arg),
("skip_while", [_]) => skip_while_next::check(cx, expr),
_ => {},
}
}
},
("nth", [n_arg]) => match method_call(recv) {
Some(("bytes", [recv2], _)) => bytes_nth::check(cx, expr, recv2, n_arg),
Some(("cloned", [recv2], _)) => iter_overeager_cloned::check(cx, expr, recv, recv2, false, false),
Some(("iter", [recv2], _)) => iter_nth::check(cx, expr, recv2, recv, n_arg, false),
Some(("iter_mut", [recv2], _)) => iter_nth::check(cx, expr, recv2, recv, n_arg, true),
_ => iter_nth_zero::check(cx, expr, recv, n_arg),
},
("ok_or_else", [arg]) => unnecessary_lazy_eval::check(cx, expr, recv, arg, "ok_or"),
("or_else", [arg]) => {
if !bind_instead_of_map::ResultOrElseErrInfo::check(cx, expr, recv, arg) {
unnecessary_lazy_eval::check(cx, expr, recv, arg, "or");
}
},
("splitn" | "rsplitn", [count_arg, pat_arg]) => {
if let Some((Constant::Int(count), _)) = constant(cx, cx.typeck_results(), count_arg) {
suspicious_splitn::check(cx, name, expr, recv, count);
str_splitn::check(cx, name, expr, recv, pat_arg, count, self.msrv);
}
},
("splitn_mut" | "rsplitn_mut", [count_arg, _]) => {
if let Some((Constant::Int(count), _)) = constant(cx, cx.typeck_results(), count_arg) {
suspicious_splitn::check(cx, name, expr, recv, count);
}
},
("step_by", [arg]) => iterator_step_by_zero::check(cx, expr, arg),
("take", [_arg]) => {
if let Some((name2, [recv2, args2 @ ..], _span2)) = method_call(recv) {
if let ("cloned", []) = (name2, args2) {
iter_overeager_cloned::check(cx, expr, recv, recv2, false, false);
}
}
},
("take", []) => needless_option_take::check(cx, expr, recv),
("then", [arg]) => {
if !meets_msrv(self.msrv, msrvs::BOOL_THEN_SOME) {
return;
}
unnecessary_lazy_eval::check(cx, expr, recv, arg, "then_some");
},
("to_os_string" | "to_owned" | "to_path_buf" | "to_vec", []) => {
implicit_clone::check(cx, name, expr, recv);
},
("unwrap", []) => {
match method_call(recv) {
Some(("get", [recv, get_arg], _)) => {
get_unwrap::check(cx, expr, recv, get_arg, false);
},
Some(("get_mut", [recv, get_arg], _)) => {
get_unwrap::check(cx, expr, recv, get_arg, true);
},
Some(("or", [recv, or_arg], or_span)) => {
or_then_unwrap::check(cx, expr, recv, or_arg, or_span);
},
_ => {},
}
unwrap_used::check(cx, expr, recv, self.allow_unwrap_in_tests);
},
("unwrap_or", [u_arg]) => match method_call(recv) {
Some((arith @ ("checked_add" | "checked_sub" | "checked_mul"), [lhs, rhs], _)) => {
manual_saturating_arithmetic::check(cx, expr, lhs, rhs, u_arg, &arith["checked_".len()..]);
},
Some(("map", [m_recv, m_arg], span)) => {
option_map_unwrap_or::check(cx, expr, m_recv, m_arg, recv, u_arg, span);
},
Some(("then_some", [t_recv, t_arg], _)) => {
obfuscated_if_else::check(cx, expr, t_recv, t_arg, u_arg);
},
_ => {},
},
("unwrap_or_else", [u_arg]) => match method_call(recv) {
Some(("map", [recv, map_arg], _))
if map_unwrap_or::check(cx, expr, recv, map_arg, u_arg, self.msrv) => {},
_ => {
unwrap_or_else_default::check(cx, expr, recv, u_arg);
unnecessary_lazy_eval::check(cx, expr, recv, u_arg, "unwrap_or");
},
},
("replace" | "replacen", [arg1, arg2] | [arg1, arg2, _]) => {
no_effect_replace::check(cx, expr, arg1, arg2);
},
_ => {},
}
}
}
}
fn check_is_some_is_none(cx: &LateContext<'_>, expr: &Expr<'_>, recv: &Expr<'_>, is_some: bool) {
if let Some((name @ ("find" | "position" | "rposition"), [f_recv, arg], span)) = method_call(recv) {
search_is_some::check(cx, expr, name, is_some, f_recv, arg, recv, span);
}
}
/// Used for `lint_binary_expr_with_method_call`.
#[derive(Copy, Clone)]
struct BinaryExprInfo<'a> {
expr: &'a hir::Expr<'a>,
chain: &'a hir::Expr<'a>,
other: &'a hir::Expr<'a>,
eq: bool,
}
/// Checks for the `CHARS_NEXT_CMP` and `CHARS_LAST_CMP` lints.
fn lint_binary_expr_with_method_call(cx: &LateContext<'_>, info: &mut BinaryExprInfo<'_>) {
macro_rules! lint_with_both_lhs_and_rhs {
($func:expr, $cx:expr, $info:ident) => {
if !$func($cx, $info) {
::std::mem::swap(&mut $info.chain, &mut $info.other);
if $func($cx, $info) {
return;
}
}
};
}
lint_with_both_lhs_and_rhs!(chars_next_cmp::check, cx, info);
lint_with_both_lhs_and_rhs!(chars_last_cmp::check, cx, info);
lint_with_both_lhs_and_rhs!(chars_next_cmp_with_unwrap::check, cx, info);
lint_with_both_lhs_and_rhs!(chars_last_cmp_with_unwrap::check, cx, info);
}
const FN_HEADER: hir::FnHeader = hir::FnHeader {
unsafety: hir::Unsafety::Normal,
constness: hir::Constness::NotConst,
asyncness: hir::IsAsync::NotAsync,
abi: rustc_target::spec::abi::Abi::Rust,
};
struct ShouldImplTraitCase {
trait_name: &'static str,
method_name: &'static str,
param_count: usize,
fn_header: hir::FnHeader,
// implicit self kind expected (none, self, &self, ...)
self_kind: SelfKind,
// checks against the output type
output_type: OutType,
// certain methods with explicit lifetimes can't implement the equivalent trait method
lint_explicit_lifetime: bool,
}
impl ShouldImplTraitCase {
const fn new(
trait_name: &'static str,
method_name: &'static str,
param_count: usize,
fn_header: hir::FnHeader,
self_kind: SelfKind,
output_type: OutType,
lint_explicit_lifetime: bool,
) -> ShouldImplTraitCase {
ShouldImplTraitCase {
trait_name,
method_name,
param_count,
fn_header,
self_kind,
output_type,
lint_explicit_lifetime,
}
}
fn lifetime_param_cond(&self, impl_item: &hir::ImplItem<'_>) -> bool {
self.lint_explicit_lifetime
|| !impl_item.generics.params.iter().any(|p| {
matches!(
p.kind,
hir::GenericParamKind::Lifetime {
kind: hir::LifetimeParamKind::Explicit
}
)
})
}
}
#[rustfmt::skip]
const TRAIT_METHODS: [ShouldImplTraitCase; 30] = [
ShouldImplTraitCase::new("std::ops::Add", "add", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
ShouldImplTraitCase::new("std::convert::AsMut", "as_mut", 1, FN_HEADER, SelfKind::RefMut, OutType::Ref, true),
ShouldImplTraitCase::new("std::convert::AsRef", "as_ref", 1, FN_HEADER, SelfKind::Ref, OutType::Ref, true),
ShouldImplTraitCase::new("std::ops::BitAnd", "bitand", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
ShouldImplTraitCase::new("std::ops::BitOr", "bitor", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
ShouldImplTraitCase::new("std::ops::BitXor", "bitxor", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
ShouldImplTraitCase::new("std::borrow::Borrow", "borrow", 1, FN_HEADER, SelfKind::Ref, OutType::Ref, true),
ShouldImplTraitCase::new("std::borrow::BorrowMut", "borrow_mut", 1, FN_HEADER, SelfKind::RefMut, OutType::Ref, true),
ShouldImplTraitCase::new("std::clone::Clone", "clone", 1, FN_HEADER, SelfKind::Ref, OutType::Any, true),
ShouldImplTraitCase::new("std::cmp::Ord", "cmp", 2, FN_HEADER, SelfKind::Ref, OutType::Any, true),
// FIXME: default doesn't work
ShouldImplTraitCase::new("std::default::Default", "default", 0, FN_HEADER, SelfKind::No, OutType::Any, true),
ShouldImplTraitCase::new("std::ops::Deref", "deref", 1, FN_HEADER, SelfKind::Ref, OutType::Ref, true),
ShouldImplTraitCase::new("std::ops::DerefMut", "deref_mut", 1, FN_HEADER, SelfKind::RefMut, OutType::Ref, true),
ShouldImplTraitCase::new("std::ops::Div", "div", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
ShouldImplTraitCase::new("std::ops::Drop", "drop", 1, FN_HEADER, SelfKind::RefMut, OutType::Unit, true),
ShouldImplTraitCase::new("std::cmp::PartialEq", "eq", 2, FN_HEADER, SelfKind::Ref, OutType::Bool, true),
ShouldImplTraitCase::new("std::iter::FromIterator", "from_iter", 1, FN_HEADER, SelfKind::No, OutType::Any, true),
ShouldImplTraitCase::new("std::str::FromStr", "from_str", 1, FN_HEADER, SelfKind::No, OutType::Any, true),
ShouldImplTraitCase::new("std::hash::Hash", "hash", 2, FN_HEADER, SelfKind::Ref, OutType::Unit, true),
ShouldImplTraitCase::new("std::ops::Index", "index", 2, FN_HEADER, SelfKind::Ref, OutType::Ref, true),
ShouldImplTraitCase::new("std::ops::IndexMut", "index_mut", 2, FN_HEADER, SelfKind::RefMut, OutType::Ref, true),
ShouldImplTraitCase::new("std::iter::IntoIterator", "into_iter", 1, FN_HEADER, SelfKind::Value, OutType::Any, true),
ShouldImplTraitCase::new("std::ops::Mul", "mul", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
ShouldImplTraitCase::new("std::ops::Neg", "neg", 1, FN_HEADER, SelfKind::Value, OutType::Any, true),
ShouldImplTraitCase::new("std::iter::Iterator", "next", 1, FN_HEADER, SelfKind::RefMut, OutType::Any, false),
ShouldImplTraitCase::new("std::ops::Not", "not", 1, FN_HEADER, SelfKind::Value, OutType::Any, true),
ShouldImplTraitCase::new("std::ops::Rem", "rem", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
ShouldImplTraitCase::new("std::ops::Shl", "shl", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
ShouldImplTraitCase::new("std::ops::Shr", "shr", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
ShouldImplTraitCase::new("std::ops::Sub", "sub", 2, FN_HEADER, SelfKind::Value, OutType::Any, true),
];
#[derive(Clone, Copy, PartialEq, Eq, Debug)]
enum SelfKind {
Value,
Ref,
RefMut,
No,
}
impl SelfKind {
fn matches<'a>(self, cx: &LateContext<'a>, parent_ty: Ty<'a>, ty: Ty<'a>) -> bool {
fn matches_value<'a>(cx: &LateContext<'a>, parent_ty: Ty<'a>, ty: Ty<'a>) -> bool {
if ty == parent_ty {
true
} else if ty.is_box() {
ty.boxed_ty() == parent_ty
} else if is_type_diagnostic_item(cx, ty, sym::Rc) || is_type_diagnostic_item(cx, ty, sym::Arc) {
if let ty::Adt(_, substs) = ty.kind() {
substs.types().next().map_or(false, |t| t == parent_ty)
} else {
false
}
} else {
false
}
}
fn matches_ref<'a>(cx: &LateContext<'a>, mutability: hir::Mutability, parent_ty: Ty<'a>, ty: Ty<'a>) -> bool {
if let ty::Ref(_, t, m) = *ty.kind() {
return m == mutability && t == parent_ty;
}
let trait_path = match mutability {
hir::Mutability::Not => &paths::ASREF_TRAIT,
hir::Mutability::Mut => &paths::ASMUT_TRAIT,
};
let trait_def_id = match get_trait_def_id(cx, trait_path) {
Some(did) => did,
None => return false,
};
implements_trait(cx, ty, trait_def_id, &[parent_ty.into()])
}
fn matches_none<'a>(cx: &LateContext<'a>, parent_ty: Ty<'a>, ty: Ty<'a>) -> bool {
!matches_value(cx, parent_ty, ty)
&& !matches_ref(cx, hir::Mutability::Not, parent_ty, ty)
&& !matches_ref(cx, hir::Mutability::Mut, parent_ty, ty)
}
match self {
Self::Value => matches_value(cx, parent_ty, ty),
Self::Ref => matches_ref(cx, hir::Mutability::Not, parent_ty, ty) || ty == parent_ty && is_copy(cx, ty),
Self::RefMut => matches_ref(cx, hir::Mutability::Mut, parent_ty, ty),
Self::No => matches_none(cx, parent_ty, ty),
}
}
#[must_use]
fn description(self) -> &'static str {
match self {
Self::Value => "`self` by value",
Self::Ref => "`self` by reference",
Self::RefMut => "`self` by mutable reference",
Self::No => "no `self`",
}
}
}
#[derive(Clone, Copy)]
enum OutType {
Unit,
Bool,
Any,
Ref,
}
impl OutType {
fn matches(self, ty: &hir::FnRetTy<'_>) -> bool {
let is_unit = |ty: &hir::Ty<'_>| matches!(ty.kind, hir::TyKind::Tup(&[]));
match (self, ty) {
(Self::Unit, &hir::FnRetTy::DefaultReturn(_)) => true,
(Self::Unit, &hir::FnRetTy::Return(ty)) if is_unit(ty) => true,
(Self::Bool, &hir::FnRetTy::Return(ty)) if is_bool(ty) => true,
(Self::Any, &hir::FnRetTy::Return(ty)) if !is_unit(ty) => true,
(Self::Ref, &hir::FnRetTy::Return(ty)) => matches!(ty.kind, hir::TyKind::Rptr(_, _)),
_ => false,
}
}
}
fn is_bool(ty: &hir::Ty<'_>) -> bool {
if let hir::TyKind::Path(QPath::Resolved(_, path)) = ty.kind {
matches!(path.res, Res::PrimTy(PrimTy::Bool))
} else {
false
}
}
fn fn_header_equals(expected: hir::FnHeader, actual: hir::FnHeader) -> bool {
expected.constness == actual.constness
&& expected.unsafety == actual.unsafety
&& expected.asyncness == actual.asyncness
}
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