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rust/clippy_lints/src/methods/mod.rs

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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_next_cmp;
mod chars_next_cmp_with_unwrap;
mod clone_on_copy;
mod clone_on_ref_ptr;
mod expect_fun_call;
mod expect_used;
mod filetype_is_file;
mod filter_flat_map;
mod filter_map;
mod filter_map_flat_map;
mod filter_map_identity;
mod filter_map_map;
mod filter_map_next;
mod filter_next;
mod flat_map_identity;
mod from_iter_instead_of_collect;
mod get_unwrap;
mod implicit_clone;
mod inefficient_to_string;
mod inspect_for_each;
mod into_iter_on_ref;
mod iter_cloned_collect;
mod iter_count;
mod iter_next_slice;
mod iter_nth;
mod iter_nth_zero;
mod iter_skip_next;
mod iterator_step_by_zero;
mod manual_saturating_arithmetic;
mod map_collect_result_unit;
mod map_flatten;
mod map_unwrap_or;
mod ok_expect;
mod option_as_ref_deref;
mod option_map_or_none;
mod option_map_unwrap_or;
mod or_fun_call;
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 string_extend_chars;
mod suspicious_map;
mod uninit_assumed_init;
mod unnecessary_filter_map;
mod unnecessary_fold;
mod unnecessary_lazy_eval;
mod unwrap_used;
mod useless_asref;
mod utils;
mod wrong_self_convention;
mod zst_offset;
use bind_instead_of_map::BindInsteadOfMap;
use clippy_utils::diagnostics::{span_lint, span_lint_and_help};
use clippy_utils::source::snippet_with_applicability;
use clippy_utils::ty::{contains_ty, implements_trait, is_copy, is_type_diagnostic_item};
use clippy_utils::{
contains_return, get_trait_def_id, in_macro, iter_input_pats, match_qpath, method_calls, paths, return_ty,
SpanlessEq,
};
use if_chain::if_chain;
use rustc_ast::ast;
use rustc_errors::Applicability;
use rustc_hir as hir;
use rustc_hir::{TraitItem, TraitItemKind};
use rustc_lint::{LateContext, LateLintPass, LintContext};
use rustc_middle::lint::in_external_macro;
use rustc_middle::ty::{self, TraitRef, Ty, TyS};
use rustc_semver::RustcVersion;
use rustc_session::{declare_tool_lint, impl_lint_pass};
use rustc_span::symbol::{sym, SymbolStr};
use rustc_typeck::hir_ty_to_ty;
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.
///
/// **Known problems:** None.
///
/// **Examples:**
/// ```rust
/// # let opt = Some(1);
///
/// // Bad
/// opt.unwrap();
///
/// // Good
/// opt.expect("more helpful message");
/// ```
///
/// // or
///
/// ```rust
/// # let res: Result<usize, ()> = Ok(1);
///
/// // Bad
/// res.unwrap();
///
/// // Good
/// res.expect("more helpful message");
/// ```
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.
///
/// **Known problems:** None.
///
/// **Examples:**
/// ```rust,ignore
/// # let opt = Some(1);
///
/// // Bad
/// opt.expect("one");
///
/// // Good
/// let opt = Some(1);
/// opt?;
/// ```
///
/// // or
///
/// ```rust
/// # let res: Result<usize, ()> = Ok(1);
///
/// // Bad
/// res.expect("one");
///
/// // Good
/// res?;
/// # Ok::<(), ()>(())
/// ```
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.
///
/// **Known problems:** None.
///
/// **Example:**
/// ```rust
/// struct X;
/// impl X {
/// fn add(&self, other: &X) -> X {
/// // ..
/// # X
/// }
/// }
/// ```
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 |
/// |-------|------------|----------------------|
/// |`as_` | none |`&self` or `&mut self`|
/// |`from_`| none | none |
/// |`into_`| none |`self` |
/// |`is_` | none |`&self` or none |
/// |`to_` | `_mut` |`&mut &self` |
/// |`to_` | not `_mut` |`&self` |
///
/// **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.
///
/// **Known problems:** None.
///
/// **Example:**
/// ```rust
/// # struct X;
/// impl X {
/// fn as_str(self) -> &'static str {
/// // ..
/// # ""
/// }
/// }
/// ```
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:** This is the same as
/// [`wrong_self_convention`](#wrong_self_convention), but for public items.
///
/// **Why is this bad?** See [`wrong_self_convention`](#wrong_self_convention).
///
/// **Known problems:** Actually *renaming* the function may break clients if
/// the function is part of the public interface. In that case, be mindful of
/// the stability guarantees you've given your users.
///
/// **Example:**
/// ```rust
/// # struct X;
/// impl<'a> X {
/// pub fn as_str(self) -> &'a str {
/// "foo"
/// }
/// }
/// ```
pub WRONG_PUB_SELF_CONVENTION,
restriction,
"defining a public 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::<_, ()>(());
///
/// // Bad
/// x.ok().expect("why did I do this again?");
///
/// // Good
/// x.expect("why did I do this again?");
/// ```
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 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 x = Some(1);
///
/// // Bad
/// x.map(|a| a + 1).unwrap_or(0);
///
/// // Good
/// x.map_or(0, |a| a + 1);
/// ```
///
/// // or
///
/// ```rust
/// # let x: Result<usize, ()> = Ok(1);
/// # fn some_function(foo: ()) -> usize { 1 }
///
/// // Bad
/// x.map(|a| a + 1).unwrap_or_else(some_function);
///
/// // Good
/// x.map_or_else(some_function, |a| a + 1);
/// ```
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);
///
/// // Bad
/// opt.map_or(None, |a| Some(a + 1));
///
/// // Good
/// opt.and_then(|a| Some(a + 1));
/// ```
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()`.
///
/// **Known problems:** None.
///
/// **Example:**
///
/// Bad:
/// ```rust
/// # let r: Result<u32, &str> = Ok(1);
/// assert_eq!(Some(1), r.map_or(None, Some));
/// ```
///
/// Good:
/// ```rust
/// # let r: Result<u32, &str> = Ok(1);
/// assert_eq!(Some(1), r.ok());
/// ```
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)`.
///
/// **Known problems:** None
///
/// **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 });
/// ```
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(_)`.
///
/// **Known problems:** None.
///
/// **Example:**
/// ```rust
/// # let vec = vec![1];
/// vec.iter().filter(|x| **x == 0).next();
/// ```
/// Could be written as
/// ```rust
/// # let vec = vec![1];
/// vec.iter().find(|x| **x == 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)`.
///
/// **Known problems:** None.
///
/// **Example:**
/// ```rust
/// # let vec = vec![1];
/// vec.iter().skip_while(|x| **x == 0).next();
/// ```
/// Could be written as
/// ```rust
/// # let vec = vec![1];
/// vec.iter().find(|x| **x != 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(_)`
///
/// **Known problems:**
///
/// **Example:**
/// ```rust
/// let vec = vec![vec![1]];
///
/// // Bad
/// vec.iter().map(|x| x.iter()).flatten();
///
/// // Good
/// vec.iter().flat_map(|x| x.iter());
/// ```
pub MAP_FLATTEN,
pedantic,
"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(_)`,
/// `_.filter(_).flat_map(_)`, `_.filter_map(_).flat_map(_)` and similar.
///
/// **Why is this bad?** Readability, this can be written more concisely as
/// `_.filter_map(_)`.
///
/// **Known problems:** Often requires a condition + Option/Iterator creation
/// inside the closure.
///
/// **Example:**
/// ```rust
/// let vec = vec![1];
///
/// // Bad
/// vec.iter().filter(|x| **x == 0).map(|x| *x * 2);
///
/// // Good
/// vec.iter().filter_map(|x| if *x == 0 {
/// Some(*x * 2)
/// } else {
/// None
/// });
/// ```
pub FILTER_MAP,
pedantic,
"using combinations of `filter`, `map`, `filter_map` and `flat_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.
///
/// **Known problems:** None.
///
/// **Example:**
/// Bad:
/// ```rust
/// (0_i32..10)
/// .filter(|n| n.checked_add(1).is_some())
/// .map(|n| n.checked_add(1).unwrap());
/// ```
///
/// Good:
/// ```rust
/// (0_i32..10).filter_map(|n| n.checked_add(1));
/// ```
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.
///
/// **Known problems:** None.
///
/// **Example:**
/// Bad:
/// ```rust
/// (0_i32..10)
/// .find(|n| n.checked_add(1).is_some())
/// .map(|n| n.checked_add(1).unwrap());
/// ```
///
/// Good:
/// ```rust
/// (0_i32..10).find_map(|n| n.checked_add(1));
/// ```
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(_)`.
///
/// **Known problems:** None
///
/// **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 });
/// ```
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`.
///
/// **Known problems:** None
///
/// **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();
/// ```
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()`.
///
/// **Why is this bad?** Readability, this can be written more concisely as
/// `_.any(_)` or `_.contains(_)`.
///
/// **Known problems:** None.
///
/// **Example:**
/// ```rust
/// # let vec = vec![1];
/// vec.iter().find(|x| **x == 0).is_some();
/// ```
/// Could be written as
/// ```rust
/// # let vec = vec![1];
/// vec.iter().any(|x| *x == 0);
/// ```
pub SEARCH_IS_SOME,
complexity,
"using an iterator or string search followed by `is_some()`, which is more succinctly expressed as a call to `any()` or `contains()`"
}
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(_)`.
///
/// **Known problems:** None.
///
/// **Example:**
/// ```rust
/// let name = "foo";
/// if name.chars().next() == Some('_') {};
/// ```
/// Could be written as
/// ```rust
/// let name = "foo";
/// if name.starts_with('_') {};
/// ```
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());
/// ```
/// this can instead be written:
/// ```rust
/// # let foo = Some(String::new());
/// foo.unwrap_or_else(String::new);
/// ```
/// or
/// ```rust
/// # let foo = Some(String::new());
/// foo.unwrap_or_default();
/// ```
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 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
/// ```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).as_str());
/// ```
/// this can instead be written:
/// ```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));
/// ```
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.
///
/// **Known problems:** None.
///
/// **Example:**
/// ```rust
/// 42u64.clone();
/// ```
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);
///
/// // Bad
/// x.clone();
///
/// // Good
/// Rc::clone(&x);
/// ```
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`.
///
/// **Known problems:** None.
///
/// **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
/// }
/// ```
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.
///
/// **Known problems:** None.
///
/// **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());
/// ```
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.
///
/// **Known problems:** None.
///
/// **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;
/// }
/// ```
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
/// // Bad
/// _.split("x");
///
/// // Good
/// _.split('x');
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.
///
/// **Known problems:** None.
///
/// **Example:**
/// ```rust,should_panic
/// for x in (0..100).step_by(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 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.
///
/// **Known problems:** None.
///
/// **Example:**
///
/// ```rust
/// # use std::collections::HashSet;
/// // Bad
/// # let mut s = HashSet::new();
/// # s.insert(1);
/// let x = s.iter().nth(0);
///
/// // Good
/// # let mut s = HashSet::new();
/// # s.insert(1);
/// let x = s.iter().next();
/// ```
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.
///
/// **Known problems:** None.
///
/// **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);
/// ```
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
///
/// **Known problems:** None.
///
/// **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);
/// ```
pub ITER_SKIP_NEXT,
style,
"using `.skip(x).next()` on an iterator"
}
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;
/// ```
pub GET_UNWRAP,
restriction,
"using `.get().unwrap()` or `.get_mut().unwrap()` when using `[]` would work instead"
}
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
///
/// **Known problems:** None.
///
/// **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);
/// ```
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
///
/// **Known problems:** None.
///
/// **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();
/// ```
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(_)`.
///
/// **Known problems:** None.
///
/// **Example:**
/// ```rust
/// # let name = "_";
///
/// // Bad
/// name.chars().last() == Some('_') || name.chars().next_back() == Some('-');
///
/// // Good
/// name.ends_with('_') || name.ends_with('-');
/// ```
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.
///
/// **Known problems:** None.
///
/// **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);
/// ```
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.
///
/// **Known problems:** None.
///
/// **Example:**
/// ```rust
/// let _ = (0..3).fold(false, |acc, x| acc || x > 2);
/// ```
/// This could be written as:
/// ```rust
/// let _ = (0..3).any(|x| x > 2);
/// ```
pub UNNECESSARY_FOLD,
style,
"using `fold` when a more succinct alternative exists"
}
declare_clippy_lint! {
/// **What it does:** Checks for `filter_map` calls which 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.
///
/// **Known problems:** None
///
/// **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);
/// ```
pub UNNECESSARY_FILTER_MAP,
complexity,
"using `filter_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.
///
/// **Known problems:** None
///
/// **Example:**
///
/// ```rust
/// // Bad
/// let _ = (&vec![3, 4, 5]).into_iter();
///
/// // Good
/// let _ = (&vec![3, 4, 5]).iter();
/// ```
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. Or, if you intend to
/// drive the iterator to completion, you can just use `for_each` instead.
///
/// **Known problems:** None
///
/// **Example:**
///
/// ```rust
/// let _ = (0..3).map(|x| x + 2).count();
/// ```
pub SUSPICIOUS_MAP,
complexity,
"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()
/// };
/// ```
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);
/// ```
pub MANUAL_SATURATING_ARITHMETIC,
style,
"`.chcked_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
///
/// **Known problems:** None
///
/// **Example:**
/// ```rust
/// unsafe { (&() as *const ()).offset(1) };
/// ```
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>(())
/// # };
/// ```
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()`.
///
/// **Known problems:** None.
///
/// **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()
/// # ;
/// ```
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()`
///
/// **Known problems:** None.
///
/// **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);
/// ```
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.
///
/// **Known problems:** None
///
/// **Example:**
/// ```rust
/// let mut string = String::new();
/// string.insert_str(0, "R");
/// string.push_str("R");
/// ```
/// Could be written as
/// ```rust
/// let mut string = String::new();
/// string.insert(0, 'R');
/// string.push('R');
/// ```
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);
/// ```
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.
///
/// **Known problems:** None
///
/// **Example:**
///
/// ```rust
/// (0..3).map(|t| Err(t)).collect::<Result<(), _>>();
/// ```
/// Use instead:
/// ```rust
/// (0..3).try_for_each(|t| Err(t));
/// ```
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)
///
/// **Known problems:** None.
///
/// **Example:**
///
/// ```rust
/// use std::iter::FromIterator;
///
/// 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]);
/// ```
pub FROM_ITER_INSTEAD_OF_COLLECT,
style,
"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`.
///
/// **Known problems:** None.
///
/// **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);
/// });
/// ```
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`.
///
/// **Known problems:** None.
///
/// **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();
/// ```
pub FILTER_MAP_IDENTITY,
complexity,
"call to `filter_map` where `flatten` is sufficient"
}
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.
///
/// **Known problems:** None.
///
/// **Example:**
///
/// ```rust
/// // Bad
/// let _ = "Hello".bytes().nth(3);
///
/// // Good
/// let _ = "Hello".as_bytes().get(3);
/// ```
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.
///
/// **Known problems:** None.
///
/// **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();
/// ```
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.
///
/// **Known problems:** None.
///
/// **Example:**
///
/// ```rust
/// // Bad
/// let some_vec = vec![0, 1, 2, 3];
/// let _ = some_vec.iter().count();
/// let _ = &some_vec[..].iter().count();
///
/// // Good
/// let some_vec = vec![0, 1, 2, 3];
/// let _ = some_vec.len();
/// let _ = &some_vec[..].len();
/// ```
pub ITER_COUNT,
complexity,
"replace `.iter().count()` with `.len()`"
}
pub struct Methods {
msrv: Option<RustcVersion>,
}
impl Methods {
#[must_use]
pub fn new(msrv: Option<RustcVersion>) -> Self {
Self { msrv }
}
}
impl_lint_pass!(Methods => [
UNWRAP_USED,
EXPECT_USED,
SHOULD_IMPLEMENT_TRAIT,
WRONG_SELF_CONVENTION,
WRONG_PUB_SELF_CONVENTION,
OK_EXPECT,
MAP_UNWRAP_OR,
RESULT_MAP_OR_INTO_OPTION,
OPTION_MAP_OR_NONE,
BIND_INSTEAD_OF_MAP,
OR_FUN_CALL,
EXPECT_FUN_CALL,
CHARS_NEXT_CMP,
CHARS_LAST_CMP,
CLONE_ON_COPY,
CLONE_ON_REF_PTR,
CLONE_DOUBLE_REF,
INEFFICIENT_TO_STRING,
NEW_RET_NO_SELF,
SINGLE_CHAR_PATTERN,
SINGLE_CHAR_ADD_STR,
SEARCH_IS_SOME,
FILTER_NEXT,
SKIP_WHILE_NEXT,
FILTER_MAP,
FILTER_MAP_IDENTITY,
MANUAL_FILTER_MAP,
MANUAL_FIND_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,
STRING_EXTEND_CHARS,
ITER_CLONED_COLLECT,
USELESS_ASREF,
UNNECESSARY_FOLD,
UNNECESSARY_FILTER_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
]);
impl<'tcx> LateLintPass<'tcx> for Methods {
#[allow(clippy::too_many_lines)]
fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>) {
if in_macro(expr.span) {
return;
}
let (method_names, arg_lists, method_spans) = method_calls(expr, 2);
let method_names: Vec<SymbolStr> = method_names.iter().map(|s| s.as_str()).collect();
let method_names: Vec<&str> = method_names.iter().map(|s| &**s).collect();
match method_names.as_slice() {
["unwrap", "get"] => get_unwrap::check(cx, expr, arg_lists[1], false),
["unwrap", "get_mut"] => get_unwrap::check(cx, expr, arg_lists[1], true),
["unwrap", ..] => unwrap_used::check(cx, expr, arg_lists[0]),
["expect", "ok"] => ok_expect::check(cx, expr, arg_lists[1]),
["expect", ..] => expect_used::check(cx, expr, arg_lists[0]),
["unwrap_or", "map"] => option_map_unwrap_or::check(cx, expr, arg_lists[1], arg_lists[0], method_spans[1]),
["unwrap_or_else", "map"] => {
if !map_unwrap_or::check(cx, expr, arg_lists[1], arg_lists[0], self.msrv.as_ref()) {
unnecessary_lazy_eval::check(cx, expr, arg_lists[0], "unwrap_or");
}
},
["map_or", ..] => option_map_or_none::check(cx, expr, arg_lists[0]),
["and_then", ..] => {
let biom_option_linted = bind_instead_of_map::OptionAndThenSome::check(cx, expr, arg_lists[0]);
let biom_result_linted = bind_instead_of_map::ResultAndThenOk::check(cx, expr, arg_lists[0]);
if !biom_option_linted && !biom_result_linted {
unnecessary_lazy_eval::check(cx, expr, arg_lists[0], "and");
}
},
["or_else", ..] => {
if !bind_instead_of_map::ResultOrElseErrInfo::check(cx, expr, arg_lists[0]) {
unnecessary_lazy_eval::check(cx, expr, arg_lists[0], "or");
}
},
["next", "filter"] => filter_next::check(cx, expr, arg_lists[1]),
["next", "skip_while"] => skip_while_next::check(cx, expr, arg_lists[1]),
["next", "iter"] => iter_next_slice::check(cx, expr, arg_lists[1]),
["map", "filter"] => filter_map::check(cx, expr, false),
["map", "filter_map"] => filter_map_map::check(cx, expr),
["next", "filter_map"] => filter_map_next::check(cx, expr, arg_lists[1], self.msrv.as_ref()),
["map", "find"] => filter_map::check(cx, expr, true),
["flat_map", "filter"] => filter_flat_map::check(cx, expr),
["flat_map", "filter_map"] => filter_map_flat_map::check(cx, expr),
["flat_map", ..] => flat_map_identity::check(cx, expr, arg_lists[0], method_spans[0]),
["flatten", "map"] => map_flatten::check(cx, expr, arg_lists[1]),
["is_some", "find"] => search_is_some::check(cx, expr, "find", arg_lists[1], arg_lists[0], method_spans[1]),
["is_some", "position"] => {
search_is_some::check(cx, expr, "position", arg_lists[1], arg_lists[0], method_spans[1])
},
["is_some", "rposition"] => {
search_is_some::check(cx, expr, "rposition", arg_lists[1], arg_lists[0], method_spans[1])
},
["extend", ..] => string_extend_chars::check(cx, expr, arg_lists[0]),
["count", "into_iter"] => iter_count::check(cx, expr, &arg_lists[1], "into_iter"),
["count", "iter"] => iter_count::check(cx, expr, &arg_lists[1], "iter"),
["count", "iter_mut"] => iter_count::check(cx, expr, &arg_lists[1], "iter_mut"),
["nth", "iter"] => iter_nth::check(cx, expr, &arg_lists, false),
["nth", "iter_mut"] => iter_nth::check(cx, expr, &arg_lists, true),
["nth", "bytes"] => bytes_nth::check(cx, expr, &arg_lists[1]),
["nth", ..] => iter_nth_zero::check(cx, expr, arg_lists[0]),
["step_by", ..] => iterator_step_by_zero::check(cx, expr, arg_lists[0]),
["next", "skip"] => iter_skip_next::check(cx, expr, arg_lists[1]),
["collect", "cloned"] => iter_cloned_collect::check(cx, expr, arg_lists[1]),
["as_ref"] => useless_asref::check(cx, expr, "as_ref", arg_lists[0]),
["as_mut"] => useless_asref::check(cx, expr, "as_mut", arg_lists[0]),
["fold", ..] => unnecessary_fold::check(cx, expr, arg_lists[0], method_spans[0]),
["filter_map", ..] => {
unnecessary_filter_map::check(cx, expr, arg_lists[0]);
filter_map_identity::check(cx, expr, arg_lists[0], method_spans[0]);
},
["count", "map"] => suspicious_map::check(cx, expr, arg_lists[1], arg_lists[0]),
["assume_init"] => uninit_assumed_init::check(cx, &arg_lists[0][0], expr),
["unwrap_or", arith @ ("checked_add" | "checked_sub" | "checked_mul")] => {
manual_saturating_arithmetic::check(cx, expr, &arg_lists, &arith["checked_".len()..])
},
["add" | "offset" | "sub" | "wrapping_offset" | "wrapping_add" | "wrapping_sub"] => {
zst_offset::check(cx, expr, arg_lists[0])
},
["is_file", ..] => filetype_is_file::check(cx, expr, arg_lists[0]),
["map", "as_ref"] => {
option_as_ref_deref::check(cx, expr, arg_lists[1], arg_lists[0], false, self.msrv.as_ref())
},
["map", "as_mut"] => {
option_as_ref_deref::check(cx, expr, arg_lists[1], arg_lists[0], true, self.msrv.as_ref())
},
["unwrap_or_else", ..] => unnecessary_lazy_eval::check(cx, expr, arg_lists[0], "unwrap_or"),
["get_or_insert_with", ..] => unnecessary_lazy_eval::check(cx, expr, arg_lists[0], "get_or_insert"),
["ok_or_else", ..] => unnecessary_lazy_eval::check(cx, expr, arg_lists[0], "ok_or"),
["collect", "map"] => map_collect_result_unit::check(cx, expr, arg_lists[1], arg_lists[0]),
["for_each", "inspect"] => inspect_for_each::check(cx, expr, method_spans[1]),
["to_owned", ..] => implicit_clone::check(cx, expr, sym::ToOwned),
["to_os_string", ..] => implicit_clone::check(cx, expr, sym::OsStr),
["to_path_buf", ..] => implicit_clone::check(cx, expr, sym::Path),
["to_vec", ..] => implicit_clone::check(cx, expr, sym::slice),
_ => {},
}
match expr.kind {
hir::ExprKind::Call(ref func, ref args) => {
from_iter_instead_of_collect::check(cx, expr, args, &func.kind);
},
hir::ExprKind::MethodCall(ref method_call, ref method_span, ref args, _) => {
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);
},
hir::ExprKind::Binary(op, ref lhs, ref 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);
// if this impl block implements a trait, lint in trait definition instead
if let hir::ItemKind::Impl(hir::Impl { of_trait: Some(_), .. }) = item.kind {
return;
}
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 cx.access_levels.is_exported(impl_item.hir_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(cx, &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
)
);
}
}
}
wrong_self_convention::check(
cx,
&name,
item.vis.node.is_pub(),
self_ty,
first_arg_ty,
first_arg.pat.span
);
}
}
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 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() {
// walk the associated type and check for Self
if contains_ty(projection_predicate.ty, self_ty) {
return;
}
}
}
}
if name == "new" && !TyS::same_type(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 let Some(first_arg_ty) = sig.decl.inputs.iter().next();
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();
then {
wrong_self_convention::check(
cx,
&item.ident.name.as_str(),
false,
self_ty,
first_arg_ty,
first_arg_span
);
}
}
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();
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);
}
/// 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!(lint_chars_last_cmp_with_unwrap, cx, info);
}
/// Checks for the `CHARS_LAST_CMP` lint with `unwrap()`.
fn lint_chars_last_cmp_with_unwrap<'tcx>(cx: &LateContext<'tcx>, info: &BinaryExprInfo<'_>) -> bool {
if chars_cmp_with_unwrap::check(cx, info, &["chars", "last", "unwrap"], CHARS_LAST_CMP, "ends_with") {
true
} else {
chars_cmp_with_unwrap::check(cx, info, &["chars", "next_back", "unwrap"], CHARS_LAST_CMP, "ends_with")
}
}
fn get_hint_if_single_char_arg(
cx: &LateContext<'_>,
arg: &hir::Expr<'_>,
applicability: &mut Applicability,
) -> Option<String> {
if_chain! {
if let hir::ExprKind::Lit(lit) = &arg.kind;
if let ast::LitKind::Str(r, style) = lit.node;
let string = r.as_str();
if string.chars().count() == 1;
then {
let snip = snippet_with_applicability(cx, arg.span, &string, applicability);
let ch = if let ast::StrStyle::Raw(nhash) = style {
let nhash = nhash as usize;
// for raw string: r##"a"##
&snip[(nhash + 2)..(snip.len() - 1 - nhash)]
} else {
// for regular string: "a"
&snip[1..(snip.len() - 1)]
};
let hint = format!("'{}'", if ch == "'" { "\\'" } else { ch });
Some(hint)
} else {
None
}
}
}
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),
];
#[rustfmt::skip]
const PATTERN_METHODS: [(&str, usize); 17] = [
("contains", 1),
("starts_with", 1),
("ends_with", 1),
("find", 1),
("rfind", 1),
("split", 1),
("rsplit", 1),
("split_terminator", 1),
("rsplit_terminator", 1),
("splitn", 2),
("rsplitn", 2),
("matches", 1),
("rmatches", 1),
("match_indices", 1),
("rmatch_indices", 1),
("trim_start_matches", 1),
("trim_end_matches", 1),
];
#[derive(Clone, Copy, PartialEq, 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<'_>, ty: Ty<'_>) -> 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()])
}
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 => ty != parent_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, cx: &LateContext<'_>, ty: &hir::FnRetTy<'_>) -> bool {
let is_unit = |ty: &hir::Ty<'_>| SpanlessEq::new(cx).eq_ty_kind(&ty.kind, &hir::TyKind::Tup(&[]));
match (self, ty) {
(Self::Unit, &hir::FnRetTy::DefaultReturn(_)) => true,
(Self::Unit, &hir::FnRetTy::Return(ref ty)) if is_unit(ty) => true,
(Self::Bool, &hir::FnRetTy::Return(ref ty)) if is_bool(ty) => true,
(Self::Any, &hir::FnRetTy::Return(ref ty)) if !is_unit(ty) => true,
(Self::Ref, &hir::FnRetTy::Return(ref ty)) => matches!(ty.kind, hir::TyKind::Rptr(_, _)),
_ => false,
}
}
}
fn is_bool(ty: &hir::Ty<'_>) -> bool {
if let hir::TyKind::Path(ref p) = ty.kind {
match_qpath(p, &["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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