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android / toolchain / rustc / 15a6560abe9880705f51d219c1fa94f880dbaf35 / . / src / tools / clippy / clippy_lints / src / methods / mod.rs
blob: eef5105409018ddb7a2e6c7ab93dee7dac790ef5 [file] [log] [blame]
mod inefficient_to_string;
mod manual_saturating_arithmetic;
mod option_map_unwrap_or;
mod unnecessary_filter_map;
use std::borrow::Cow;
use std::fmt;
use std::iter;
use if_chain::if_chain;
use matches::matches;
use rustc::hir::map::Map;
use rustc::lint::in_external_macro;
use rustc::ty::{self, Predicate, Ty};
use rustc_ast::ast;
use rustc_errors::Applicability;
use rustc_hir as hir;
use rustc_hir::intravisit::{self, Visitor};
use rustc_lint::{LateContext, LateLintPass, Lint, LintContext};
use rustc_session::{declare_lint_pass, declare_tool_lint};
use rustc_span::source_map::Span;
use rustc_span::symbol::{sym, Symbol, SymbolStr};
use crate::consts::{constant, Constant};
use crate::utils::usage::mutated_variables;
use crate::utils::{
get_arg_name, get_parent_expr, get_trait_def_id, has_iter_method, implements_trait, in_macro, is_copy,
is_ctor_or_promotable_const_function, is_expn_of, is_type_diagnostic_item, iter_input_pats, last_path_segment,
match_def_path, match_qpath, match_trait_method, match_type, match_var, method_calls, method_chain_args, paths,
remove_blocks, return_ty, same_tys, single_segment_path, snippet, snippet_with_applicability,
snippet_with_macro_callsite, span_lint, span_lint_and_help, span_lint_and_note, span_lint_and_sugg,
span_lint_and_then, sugg, walk_ptrs_ty, walk_ptrs_ty_depth, SpanlessEq,
};
declare_clippy_lint! {
/// **What it does:** Checks for `.unwrap()` calls on `Option`s.
///
/// **Why is this bad?** Usually it is better to handle the `None` case, or to
/// 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.
///
/// **Known problems:** None.
///
/// **Example:**
///
/// Using unwrap on an `Option`:
///
/// ```rust
/// let opt = Some(1);
/// opt.unwrap();
/// ```
///
/// Better:
///
/// ```rust
/// let opt = Some(1);
/// opt.expect("more helpful message");
/// ```
pub OPTION_UNWRAP_USED,
restriction,
"using `Option.unwrap()`, which should at least get a better message using `expect()`"
}
declare_clippy_lint! {
/// **What it does:** Checks for `.unwrap()` calls on `Result`s.
///
/// **Why is this bad?** `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.
///
/// **Example:**
/// Using unwrap on an `Result`:
///
/// ```rust
/// let res: Result<usize, ()> = Ok(1);
/// res.unwrap();
/// ```
///
/// Better:
///
/// ```rust
/// let res: Result<usize, ()> = Ok(1);
/// res.expect("more helpful message");
/// ```
pub RESULT_UNWRAP_USED,
restriction,
"using `Result.unwrap()`, which might be better handled"
}
declare_clippy_lint! {
/// **What it does:** Checks for `.expect()` calls on `Option`s.
///
/// **Why is this bad?** Usually it is better to handle the `None` case. Still,
/// for a lot of quick-and-dirty code, `expect` is a good choice, which is why
/// this lint is `Allow` by default.
///
/// **Known problems:** None.
///
/// **Example:**
///
/// Using expect on an `Option`:
///
/// ```rust
/// let opt = Some(1);
/// opt.expect("one");
/// ```
///
/// Better:
///
/// ```rust,ignore
/// let opt = Some(1);
/// opt?;
/// ```
pub OPTION_EXPECT_USED,
restriction,
"using `Option.expect()`, which might be better handled"
}
declare_clippy_lint! {
/// **What it does:** Checks for `.expect()` calls on `Result`s.
///
/// **Why is this bad?** `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.
///
/// **Example:**
/// Using expect on an `Result`:
///
/// ```rust
/// let res: Result<usize, ()> = Ok(1);
/// res.expect("one");
/// ```
///
/// Better:
///
/// ```rust
/// let res: Result<usize, ()> = Ok(1);
/// res?;
/// # Ok::<(), ()>(())
/// ```
pub RESULT_EXPECT_USED,
restriction,
"using `Result.expect()`, 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 |`self` taken |
/// |-------|----------------------|
/// |`as_` |`&self` or `&mut self`|
/// |`from_`| none |
/// |`into_`|`self` |
/// |`is_` |`&self` or none |
/// |`to_` |`&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::<_, ()>(());
/// x.ok().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 `_.map(_).unwrap_or(_)`.
///
/// **Why is this bad?** Readability, this can be written more concisely as
/// `_.map_or(_, _)`.
///
/// **Known problems:** The order of the arguments is not in execution order
///
/// **Example:**
/// ```rust
/// # let x = Some(1);
/// x.map(|a| a + 1).unwrap_or(0);
/// ```
pub OPTION_MAP_UNWRAP_OR,
pedantic,
"using `Option.map(f).unwrap_or(a)`, which is more succinctly expressed as `map_or(a, f)`"
}
declare_clippy_lint! {
/// **What it does:** Checks for usage of `_.map(_).unwrap_or_else(_)`.
///
/// **Why is this bad?** Readability, this can be written more concisely as
/// `_.map_or_else(_, _)`.
///
/// **Known problems:** The order of the arguments is not in execution order.
///
/// **Example:**
/// ```rust
/// # let x = Some(1);
/// # fn some_function() -> usize { 1 }
/// x.map(|a| a + 1).unwrap_or_else(some_function);
/// ```
pub OPTION_MAP_UNWRAP_OR_ELSE,
pedantic,
"using `Option.map(f).unwrap_or_else(g)`, which is more succinctly expressed as `map_or_else(g, f)`"
}
declare_clippy_lint! {
/// **What it does:** Checks for usage of `result.map(_).unwrap_or_else(_)`.
///
/// **Why is this bad?** Readability, this can be written more concisely as
/// `result.map_or_else(_, _)`.
///
/// **Known problems:** None.
///
/// **Example:**
/// ```rust
/// # let x: Result<usize, ()> = Ok(1);
/// # fn some_function(foo: ()) -> usize { 1 }
/// x.map(|a| a + 1).unwrap_or_else(some_function);
/// ```
pub RESULT_MAP_UNWRAP_OR_ELSE,
pedantic,
"using `Result.map(f).unwrap_or_else(g)`, which is more succinctly expressed as `.map_or_else(g, 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))
/// # ;
/// ```
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 `_.and_then(|x| Some(y))`.
///
/// **Why is this bad?** Readability, this can be written more concisely as
/// `_.map(|x| y)`.
///
/// **Known problems:** None
///
/// **Example:**
///
/// ```rust
/// let x = Some("foo");
/// let _ = x.and_then(|s| Some(s.len()));
/// ```
///
/// The correct use would be:
///
/// ```rust
/// let x = Some("foo");
/// let _ = x.map(|s| s.len());
/// ```
pub OPTION_AND_THEN_SOME,
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(_)`,
///
/// **Why is this bad?** Readability, this can be written more concisely as a
/// single method call.
///
/// **Known problems:**
///
/// **Example:**
/// ```rust
/// let vec = vec![vec![1]];
/// vec.iter().map(|x| x.iter()).flatten();
/// ```
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 a
/// single method call.
///
/// **Known problems:** Often requires a condition + Option/Iterator creation
/// inside the closure.
///
/// **Example:**
/// ```rust
/// let vec = vec![1];
/// vec.iter().filter(|x| **x == 0).map(|x| *x * 2);
/// ```
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(_).next()`.
///
/// **Why is this bad?** Readability, this can be written more concisely as a
/// single method call.
///
/// **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 usage of `_.find(_).map(_)`.
///
/// **Why is this bad?** Readability, this can be written more concisely as a
/// single method call.
///
/// **Known problems:** Often requires a condition + Option/Iterator creation
/// inside the closure.
///
/// **Example:**
/// ```rust
/// (0..3).find(|x| *x == 2).map(|x| x * 2);
/// ```
/// Can be written as
/// ```rust
/// (0..3).find_map(|x| if x == 2 { Some(x * 2) } else { None });
/// ```
pub FIND_MAP,
pedantic,
"using a combination of `find` and `map` can usually be written as a single method call"
}
declare_clippy_lint! {
/// **What it does:** Checks for an iterator 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(_)`.
///
/// **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 search followed by `is_some()`, which is more succinctly expressed as a call to `any()`"
}
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);
/// x.clone();
/// ```
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,
perf,
"using `to_string` on `&&T` where `T: ToString`"
}
declare_clippy_lint! {
/// **What it does:** Checks for `new` not returning `Self`.
///
/// **Why is this bad?** As a convention, `new` methods are used to make a new
/// instance of a type.
///
/// **Known problems:** None.
///
/// **Example:**
/// ```rust
/// # struct Foo;
/// # struct NotAFoo;
/// impl Foo {
/// fn new() -> NotAFoo {
/// # NotAFoo
/// }
/// }
/// ```
pub NEW_RET_NO_SELF,
style,
"not returning `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:**
/// `_.split("x")` could be `_.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 getting the inner pointer of a temporary
/// `CString`.
///
/// **Why is this bad?** The inner pointer of a `CString` is only valid as long
/// as the `CString` is alive.
///
/// **Known problems:** None.
///
/// **Example:**
/// ```rust
/// # use std::ffi::CString;
/// # fn call_some_ffi_func(_: *const i8) {}
/// #
/// let c_str = CString::new("foo").unwrap().as_ptr();
/// unsafe {
/// call_some_ffi_func(c_str);
/// }
/// ```
/// Here `c_str` point to a freed address. The correct use would be:
/// ```rust
/// # use std::ffi::CString;
/// # fn call_some_ffi_func(_: *const i8) {}
/// #
/// let c_str = CString::new("foo").unwrap();
/// unsafe {
/// call_some_ffi_func(c_str.as_ptr());
/// }
/// ```
pub TEMPORARY_CSTRING_AS_PTR,
correctness,
"getting the inner pointer of a temporary `CString`"
}
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 = "_";
/// name.chars().last() == Some('_') || name.chars().next_back() == Some('-')
/// # ;
/// ```
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:** False positive in pattern guards. Will be resolved once
/// non-lexical lifetimes are stable.
///
/// **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:
/// ```rust
/// 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:
/// ```rust
/// 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
/// let _ = (&vec![3, 4, 5]).into_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_value());
/// let sub = x.checked_sub(y).unwrap_or(u32::min_value());
/// ```
///
/// 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 a
/// single method call.
///
/// **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_lint_pass!(Methods => [
OPTION_UNWRAP_USED,
RESULT_UNWRAP_USED,
OPTION_EXPECT_USED,
RESULT_EXPECT_USED,
SHOULD_IMPLEMENT_TRAIT,
WRONG_SELF_CONVENTION,
WRONG_PUB_SELF_CONVENTION,
OK_EXPECT,
OPTION_MAP_UNWRAP_OR,
OPTION_MAP_UNWRAP_OR_ELSE,
RESULT_MAP_UNWRAP_OR_ELSE,
OPTION_MAP_OR_NONE,
OPTION_AND_THEN_SOME,
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,
SEARCH_IS_SOME,
TEMPORARY_CSTRING_AS_PTR,
FILTER_NEXT,
SKIP_WHILE_NEXT,
FILTER_MAP,
FILTER_MAP_NEXT,
FLAT_MAP_IDENTITY,
FIND_MAP,
MAP_FLATTEN,
ITERATOR_STEP_BY_ZERO,
ITER_NTH,
ITER_NTH_ZERO,
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,
]);
impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Methods {
#[allow(clippy::cognitive_complexity, clippy::too_many_lines)]
fn check_expr(&mut self, cx: &LateContext<'a, '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"] => lint_get_unwrap(cx, expr, arg_lists[1], false),
["unwrap", "get_mut"] => lint_get_unwrap(cx, expr, arg_lists[1], true),
["unwrap", ..] => lint_unwrap(cx, expr, arg_lists[0]),
["expect", "ok"] => lint_ok_expect(cx, expr, arg_lists[1]),
["expect", ..] => lint_expect(cx, expr, arg_lists[0]),
["unwrap_or", "map"] => option_map_unwrap_or::lint(cx, expr, arg_lists[1], arg_lists[0], method_spans[1]),
["unwrap_or_else", "map"] => lint_map_unwrap_or_else(cx, expr, arg_lists[1], arg_lists[0]),
["map_or", ..] => lint_map_or_none(cx, expr, arg_lists[0]),
["and_then", ..] => lint_option_and_then_some(cx, expr, arg_lists[0]),
["next", "filter"] => lint_filter_next(cx, expr, arg_lists[1]),
["next", "skip_while"] => lint_skip_while_next(cx, expr, arg_lists[1]),
["map", "filter"] => lint_filter_map(cx, expr, arg_lists[1], arg_lists[0]),
["map", "filter_map"] => lint_filter_map_map(cx, expr, arg_lists[1], arg_lists[0]),
["next", "filter_map"] => lint_filter_map_next(cx, expr, arg_lists[1]),
["map", "find"] => lint_find_map(cx, expr, arg_lists[1], arg_lists[0]),
["flat_map", "filter"] => lint_filter_flat_map(cx, expr, arg_lists[1], arg_lists[0]),
["flat_map", "filter_map"] => lint_filter_map_flat_map(cx, expr, arg_lists[1], arg_lists[0]),
["flat_map", ..] => lint_flat_map_identity(cx, expr, arg_lists[0], method_spans[0]),
["flatten", "map"] => lint_map_flatten(cx, expr, arg_lists[1]),
["is_some", "find"] => lint_search_is_some(cx, expr, "find", arg_lists[1], arg_lists[0], method_spans[1]),
["is_some", "position"] => {
lint_search_is_some(cx, expr, "position", arg_lists[1], arg_lists[0], method_spans[1])
},
["is_some", "rposition"] => {
lint_search_is_some(cx, expr, "rposition", arg_lists[1], arg_lists[0], method_spans[1])
},
["extend", ..] => lint_extend(cx, expr, arg_lists[0]),
["as_ptr", "unwrap"] | ["as_ptr", "expect"] => {
lint_cstring_as_ptr(cx, expr, &arg_lists[1][0], &arg_lists[0][0])
},
["nth", "iter"] => lint_iter_nth(cx, expr, &arg_lists, false),
["nth", "iter_mut"] => lint_iter_nth(cx, expr, &arg_lists, true),
["nth", ..] => lint_iter_nth_zero(cx, expr, arg_lists[0]),
["step_by", ..] => lint_step_by(cx, expr, arg_lists[0]),
["next", "skip"] => lint_iter_skip_next(cx, expr),
["collect", "cloned"] => lint_iter_cloned_collect(cx, expr, arg_lists[1]),
["as_ref"] => lint_asref(cx, expr, "as_ref", arg_lists[0]),
["as_mut"] => lint_asref(cx, expr, "as_mut", arg_lists[0]),
["fold", ..] => lint_unnecessary_fold(cx, expr, arg_lists[0], method_spans[0]),
["filter_map", ..] => unnecessary_filter_map::lint(cx, expr, arg_lists[0]),
["count", "map"] => lint_suspicious_map(cx, expr),
["assume_init"] => lint_maybe_uninit(cx, &arg_lists[0][0], expr),
["unwrap_or", arith @ "checked_add"]
| ["unwrap_or", arith @ "checked_sub"]
| ["unwrap_or", arith @ "checked_mul"] => {
manual_saturating_arithmetic::lint(cx, expr, &arg_lists, &arith["checked_".len()..])
},
["add"] | ["offset"] | ["sub"] | ["wrapping_offset"] | ["wrapping_add"] | ["wrapping_sub"] => {
check_pointer_offset(cx, expr, arg_lists[0])
},
["is_file", ..] => lint_filetype_is_file(cx, expr, arg_lists[0]),
["map", "as_ref"] => lint_option_as_ref_deref(cx, expr, arg_lists[1], arg_lists[0], false),
["map", "as_mut"] => lint_option_as_ref_deref(cx, expr, arg_lists[1], arg_lists[0], true),
_ => {},
}
match expr.kind {
hir::ExprKind::MethodCall(ref method_call, ref method_span, ref args) => {
lint_or_fun_call(cx, expr, *method_span, &method_call.ident.as_str(), args);
lint_expect_fun_call(cx, expr, *method_span, &method_call.ident.as_str(), args);
let self_ty = cx.tables.expr_ty_adjusted(&args[0]);
if args.len() == 1 && method_call.ident.name == sym!(clone) {
lint_clone_on_copy(cx, expr, &args[0], self_ty);
lint_clone_on_ref_ptr(cx, expr, &args[0]);
}
if args.len() == 1 && method_call.ident.name == sym!(to_string) {
inefficient_to_string::lint(cx, expr, &args[0], self_ty);
}
match self_ty.kind {
ty::Ref(_, ty, _) if ty.kind == ty::Str => {
for &(method, pos) in &PATTERN_METHODS {
if method_call.ident.name.as_str() == method && args.len() > pos {
lint_single_char_pattern(cx, expr, &args[pos]);
}
}
},
ty::Ref(..) if method_call.ident.name == sym!(into_iter) => {
lint_into_iter(cx, expr, self_ty, *method_span);
},
_ => (),
}
},
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);
}
_ => (),
}
}
fn check_impl_item(&mut self, cx: &LateContext<'a, '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 def_id = cx.tcx.hir().local_def_id(item.hir_id);
let ty = cx.tcx.type_of(def_id);
if_chain! {
if let hir::ImplItemKind::Method(ref sig, id) = impl_item.kind;
if let Some(first_arg) = iter_input_pats(&sig.decl, cx.tcx.hir().body(id)).next();
if let hir::ItemKind::Impl{ of_trait: None, .. } = item.kind;
let method_def_id = cx.tcx.hir().local_def_id(impl_item.hir_id);
let method_sig = cx.tcx.fn_sig(method_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_name, n_args, self_kind, out_type, trait_name) in &TRAIT_METHODS {
if name == method_name &&
sig.decl.inputs.len() == n_args &&
out_type.matches(cx, &sig.decl.output) &&
self_kind.matches(cx, ty, first_arg_ty) {
span_lint(cx, SHOULD_IMPLEMENT_TRAIT, impl_item.span, &format!(
"defining a method called `{}` on this type; consider implementing \
the `{}` trait or choosing a less ambiguous name", name, trait_name));
}
}
}
if let Some((ref conv, self_kinds)) = &CONVENTIONS
.iter()
.find(|(ref conv, _)| conv.check(&name))
{
if !self_kinds.iter().any(|k| k.matches(cx, ty, first_arg_ty)) {
let lint = if item.vis.node.is_pub() {
WRONG_PUB_SELF_CONVENTION
} else {
WRONG_SELF_CONVENTION
};
span_lint(
cx,
lint,
first_arg.pat.span,
&format!(
"methods called `{}` usually take {}; consider choosing a less \
ambiguous name",
conv,
&self_kinds
.iter()
.map(|k| k.description())
.collect::<Vec<_>>()
.join(" or ")
),
);
}
}
}
}
if let hir::ImplItemKind::Method(_, _) = 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 ret_ty.walk().any(|inner_type| same_tys(cx, ty, inner_type)) {
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 in cx.tcx.predicates_of(def_id).predicates {
match predicate {
(Predicate::Projection(poly_projection_predicate), _) => {
let binder = poly_projection_predicate.ty();
let associated_type = binder.skip_binder();
// walk the associated type and check for Self
for inner_type in associated_type.walk() {
if same_tys(cx, ty, inner_type) {
return;
}
}
},
(_, _) => {},
}
}
}
if name == "new" && !same_tys(cx, ret_ty, ty) {
span_lint(
cx,
NEW_RET_NO_SELF,
impl_item.span,
"methods called `new` usually return `Self`",
);
}
}
}
}
/// Checks for the `OR_FUN_CALL` lint.
#[allow(clippy::too_many_lines)]
fn lint_or_fun_call<'a, 'tcx>(
cx: &LateContext<'a, 'tcx>,
expr: &hir::Expr<'_>,
method_span: Span,
name: &str,
args: &'tcx [hir::Expr<'_>],
) {
// Searches an expression for method calls or function calls that aren't ctors
struct FunCallFinder<'a, 'tcx> {
cx: &'a LateContext<'a, 'tcx>,
found: bool,
}
impl<'a, 'tcx> intravisit::Visitor<'tcx> for FunCallFinder<'a, 'tcx> {
type Map = Map<'tcx>;
fn visit_expr(&mut self, expr: &'tcx hir::Expr<'_>) {
let call_found = match &expr.kind {
// ignore enum and struct constructors
hir::ExprKind::Call(..) => !is_ctor_or_promotable_const_function(self.cx, expr),
hir::ExprKind::MethodCall(..) => true,
_ => false,
};
if call_found {
self.found |= true;
}
if !self.found {
intravisit::walk_expr(self, expr);
}
}
fn nested_visit_map(&mut self) -> intravisit::NestedVisitorMap<'_, Self::Map> {
intravisit::NestedVisitorMap::None
}
}
/// Checks for `unwrap_or(T::new())` or `unwrap_or(T::default())`.
fn check_unwrap_or_default(
cx: &LateContext<'_, '_>,
name: &str,
fun: &hir::Expr<'_>,
self_expr: &hir::Expr<'_>,
arg: &hir::Expr<'_>,
or_has_args: bool,
span: Span,
) -> bool {
if_chain! {
if !or_has_args;
if name == "unwrap_or";
if let hir::ExprKind::Path(ref qpath) = fun.kind;
let path = &*last_path_segment(qpath).ident.as_str();
if ["default", "new"].contains(&path);
let arg_ty = cx.tables.expr_ty(arg);
if let Some(default_trait_id) = get_trait_def_id(cx, &paths::DEFAULT_TRAIT);
if implements_trait(cx, arg_ty, default_trait_id, &[]);
then {
let mut applicability = Applicability::MachineApplicable;
span_lint_and_sugg(
cx,
OR_FUN_CALL,
span,
&format!("use of `{}` followed by a call to `{}`", name, path),
"try this",
format!(
"{}.unwrap_or_default()",
snippet_with_applicability(cx, self_expr.span, "_", &mut applicability)
),
applicability,
);
true
} else {
false
}
}
}
/// Checks for `*or(foo())`.
#[allow(clippy::too_many_arguments)]
fn check_general_case<'a, 'tcx>(
cx: &LateContext<'a, 'tcx>,
name: &str,
method_span: Span,
fun_span: Span,
self_expr: &hir::Expr<'_>,
arg: &'tcx hir::Expr<'_>,
or_has_args: bool,
span: Span,
) {
// (path, fn_has_argument, methods, suffix)
let know_types: &[(&[_], _, &[_], _)] = &[
(&paths::BTREEMAP_ENTRY, false, &["or_insert"], "with"),
(&paths::HASHMAP_ENTRY, false, &["or_insert"], "with"),
(&paths::OPTION, false, &["map_or", "ok_or", "or", "unwrap_or"], "else"),
(&paths::RESULT, true, &["or", "unwrap_or"], "else"),
];
if_chain! {
if know_types.iter().any(|k| k.2.contains(&name));
let mut finder = FunCallFinder { cx: &cx, found: false };
if { finder.visit_expr(&arg); finder.found };
if !contains_return(&arg);
let self_ty = cx.tables.expr_ty(self_expr);
if let Some(&(_, fn_has_arguments, poss, suffix)) =
know_types.iter().find(|&&i| match_type(cx, self_ty, i.0));
if poss.contains(&name);
then {
let sugg: Cow<'_, _> = match (fn_has_arguments, !or_has_args) {
(true, _) => format!("|_| {}", snippet_with_macro_callsite(cx, arg.span, "..")).into(),
(false, false) => format!("|| {}", snippet_with_macro_callsite(cx, arg.span, "..")).into(),
(false, true) => snippet_with_macro_callsite(cx, fun_span, ".."),
};
let span_replace_word = method_span.with_hi(span.hi());
span_lint_and_sugg(
cx,
OR_FUN_CALL,
span_replace_word,
&format!("use of `{}` followed by a function call", name),
"try this",
format!("{}_{}({})", name, suffix, sugg),
Applicability::HasPlaceholders,
);
}
}
}
if args.len() == 2 {
match args[1].kind {
hir::ExprKind::Call(ref fun, ref or_args) => {
let or_has_args = !or_args.is_empty();
if !check_unwrap_or_default(cx, name, fun, &args[0], &args[1], or_has_args, expr.span) {
check_general_case(
cx,
name,
method_span,
fun.span,
&args[0],
&args[1],
or_has_args,
expr.span,
);
}
},
hir::ExprKind::MethodCall(_, span, ref or_args) => check_general_case(
cx,
name,
method_span,
span,
&args[0],
&args[1],
!or_args.is_empty(),
expr.span,
),
_ => {},
}
}
}
/// Checks for the `EXPECT_FUN_CALL` lint.
#[allow(clippy::too_many_lines)]
fn lint_expect_fun_call(
cx: &LateContext<'_, '_>,
expr: &hir::Expr<'_>,
method_span: Span,
name: &str,
args: &[hir::Expr<'_>],
) {
// Strip `&`, `as_ref()` and `as_str()` off `arg` until we're left with either a `String` or
// `&str`
fn get_arg_root<'a>(cx: &LateContext<'_, '_>, arg: &'a hir::Expr<'a>) -> &'a hir::Expr<'a> {
let mut arg_root = arg;
loop {
arg_root = match &arg_root.kind {
hir::ExprKind::AddrOf(hir::BorrowKind::Ref, _, expr) => expr,
hir::ExprKind::MethodCall(method_name, _, call_args) => {
if call_args.len() == 1
&& (method_name.ident.name == sym!(as_str) || method_name.ident.name == sym!(as_ref))
&& {
let arg_type = cx.tables.expr_ty(&call_args[0]);
let base_type = walk_ptrs_ty(arg_type);
base_type.kind == ty::Str || match_type(cx, base_type, &paths::STRING)
}
{
&call_args[0]
} else {
break;
}
},
_ => break,
};
}
arg_root
}
// Only `&'static str` or `String` can be used directly in the `panic!`. Other types should be
// converted to string.
fn requires_to_string(cx: &LateContext<'_, '_>, arg: &hir::Expr<'_>) -> bool {
let arg_ty = cx.tables.expr_ty(arg);
if match_type(cx, arg_ty, &paths::STRING) {
return false;
}
if let ty::Ref(_, ty, ..) = arg_ty.kind {
if ty.kind == ty::Str && can_be_static_str(cx, arg) {
return false;
}
};
true
}
// Check if an expression could have type `&'static str`, knowing that it
// has type `&str` for some lifetime.
fn can_be_static_str(cx: &LateContext<'_, '_>, arg: &hir::Expr<'_>) -> bool {
match arg.kind {
hir::ExprKind::Lit(_) => true,
hir::ExprKind::Call(fun, _) => {
if let hir::ExprKind::Path(ref p) = fun.kind {
match cx.tables.qpath_res(p, fun.hir_id) {
hir::def::Res::Def(hir::def::DefKind::Fn, def_id)
| hir::def::Res::Def(hir::def::DefKind::Method, def_id) => matches!(
cx.tcx.fn_sig(def_id).output().skip_binder().kind,
ty::Ref(ty::ReStatic, ..)
),
_ => false,
}
} else {
false
}
},
hir::ExprKind::MethodCall(..) => cx.tables.type_dependent_def_id(arg.hir_id).map_or(false, |method_id| {
matches!(
cx.tcx.fn_sig(method_id).output().skip_binder().kind,
ty::Ref(ty::ReStatic, ..)
)
}),
hir::ExprKind::Path(ref p) => match cx.tables.qpath_res(p, arg.hir_id) {
hir::def::Res::Def(hir::def::DefKind::Const, _) | hir::def::Res::Def(hir::def::DefKind::Static, _) => {
true
},
_ => false,
},
_ => false,
}
}
fn generate_format_arg_snippet(
cx: &LateContext<'_, '_>,
a: &hir::Expr<'_>,
applicability: &mut Applicability,
) -> Vec<String> {
if_chain! {
if let hir::ExprKind::AddrOf(hir::BorrowKind::Ref, _, ref format_arg) = a.kind;
if let hir::ExprKind::Match(ref format_arg_expr, _, _) = format_arg.kind;
if let hir::ExprKind::Tup(ref format_arg_expr_tup) = format_arg_expr.kind;
then {
format_arg_expr_tup
.iter()
.map(|a| snippet_with_applicability(cx, a.span, "..", applicability).into_owned())
.collect()
} else {
unreachable!()
}
}
}
fn is_call(node: &hir::ExprKind<'_>) -> bool {
match node {
hir::ExprKind::AddrOf(hir::BorrowKind::Ref, _, expr) => {
is_call(&expr.kind)
},
hir::ExprKind::Call(..)
| hir::ExprKind::MethodCall(..)
// These variants are debatable or require further examination
| hir::ExprKind::Match(..)
| hir::ExprKind::Block{ .. } => true,
_ => false,
}
}
if args.len() != 2 || name != "expect" || !is_call(&args[1].kind) {
return;
}
let receiver_type = cx.tables.expr_ty_adjusted(&args[0]);
let closure_args = if match_type(cx, receiver_type, &paths::OPTION) {
"||"
} else if match_type(cx, receiver_type, &paths::RESULT) {
"|_|"
} else {
return;
};
let arg_root = get_arg_root(cx, &args[1]);
let span_replace_word = method_span.with_hi(expr.span.hi());
let mut applicability = Applicability::MachineApplicable;
//Special handling for `format!` as arg_root
if_chain! {
if let hir::ExprKind::Block(block, None) = &arg_root.kind;
if block.stmts.len() == 1;
if let hir::StmtKind::Local(local) = &block.stmts[0].kind;
if let Some(arg_root) = &local.init;
if let hir::ExprKind::Call(ref inner_fun, ref inner_args) = arg_root.kind;
if is_expn_of(inner_fun.span, "format").is_some() && inner_args.len() == 1;
if let hir::ExprKind::Call(_, format_args) = &inner_args[0].kind;
then {
let fmt_spec = &format_args[0];
let fmt_args = &format_args[1];
let mut args = vec![snippet(cx, fmt_spec.span, "..").into_owned()];
args.extend(generate_format_arg_snippet(cx, fmt_args, &mut applicability));
let sugg = args.join(", ");
span_lint_and_sugg(
cx,
EXPECT_FUN_CALL,
span_replace_word,
&format!("use of `{}` followed by a function call", name),
"try this",
format!("unwrap_or_else({} panic!({}))", closure_args, sugg),
applicability,
);
return;
}
}
let mut arg_root_snippet: Cow<'_, _> = snippet_with_applicability(cx, arg_root.span, "..", &mut applicability);
if requires_to_string(cx, arg_root) {
arg_root_snippet.to_mut().push_str(".to_string()");
}
span_lint_and_sugg(
cx,
EXPECT_FUN_CALL,
span_replace_word,
&format!("use of `{}` followed by a function call", name),
"try this",
format!("unwrap_or_else({} {{ panic!({}) }})", closure_args, arg_root_snippet),
applicability,
);
}
/// Checks for the `CLONE_ON_COPY` lint.
fn lint_clone_on_copy(cx: &LateContext<'_, '_>, expr: &hir::Expr<'_>, arg: &hir::Expr<'_>, arg_ty: Ty<'_>) {
let ty = cx.tables.expr_ty(expr);
if let ty::Ref(_, inner, _) = arg_ty.kind {
if let ty::Ref(_, innermost, _) = inner.kind {
span_lint_and_then(
cx,
CLONE_DOUBLE_REF,
expr.span,
"using `clone` on a double-reference; \
this will copy the reference instead of cloning the inner type",
|db| {
if let Some(snip) = sugg::Sugg::hir_opt(cx, arg) {
let mut ty = innermost;
let mut n = 0;
while let ty::Ref(_, inner, _) = ty.kind {
ty = inner;
n += 1;
}
let refs: String = iter::repeat('&').take(n + 1).collect();
let derefs: String = iter::repeat('*').take(n).collect();
let explicit = format!("{}{}::clone({})", refs, ty, snip);
db.span_suggestion(
expr.span,
"try dereferencing it",
format!("{}({}{}).clone()", refs, derefs, snip.deref()),
Applicability::MaybeIncorrect,
);
db.span_suggestion(
expr.span,
"or try being explicit about what type to clone",
explicit,
Applicability::MaybeIncorrect,
);
}
},
);
return; // don't report clone_on_copy
}
}
if is_copy(cx, ty) {
let snip;
if let Some(snippet) = sugg::Sugg::hir_opt(cx, arg) {
let parent = cx.tcx.hir().get_parent_node(expr.hir_id);
match &cx.tcx.hir().get(parent) {
hir::Node::Expr(parent) => match parent.kind {
// &*x is a nop, &x.clone() is not
hir::ExprKind::AddrOf(..) |
// (*x).func() is useless, x.clone().func() can work in case func borrows mutably
hir::ExprKind::MethodCall(..) => return,
_ => {},
},
hir::Node::Stmt(stmt) => {
if let hir::StmtKind::Local(ref loc) = stmt.kind {
if let hir::PatKind::Ref(..) = loc.pat.kind {
// let ref y = *x borrows x, let ref y = x.clone() does not
return;
}
}
},
_ => {},
}
// x.clone() might have dereferenced x, possibly through Deref impls
if cx.tables.expr_ty(arg) == ty {
snip = Some(("try removing the `clone` call", format!("{}", snippet)));
} else {
let deref_count = cx
.tables
.expr_adjustments(arg)
.iter()
.filter(|adj| {
if let ty::adjustment::Adjust::Deref(_) = adj.kind {
true
} else {
false
}
})
.count();
let derefs: String = iter::repeat('*').take(deref_count).collect();
snip = Some(("try dereferencing it", format!("{}{}", derefs, snippet)));
}
} else {
snip = None;
}
span_lint_and_then(cx, CLONE_ON_COPY, expr.span, "using `clone` on a `Copy` type", |db| {
if let Some((text, snip)) = snip {
db.span_suggestion(expr.span, text, snip, Applicability::Unspecified);
}
});
}
}
fn lint_clone_on_ref_ptr(cx: &LateContext<'_, '_>, expr: &hir::Expr<'_>, arg: &hir::Expr<'_>) {
let obj_ty = walk_ptrs_ty(cx.tables.expr_ty(arg));
if let ty::Adt(_, subst) = obj_ty.kind {
let caller_type = if match_type(cx, obj_ty, &paths::RC) {
"Rc"
} else if match_type(cx, obj_ty, &paths::ARC) {
"Arc"
} else if match_type(cx, obj_ty, &paths::WEAK_RC) || match_type(cx, obj_ty, &paths::WEAK_ARC) {
"Weak"
} else {
return;
};
span_lint_and_sugg(
cx,
CLONE_ON_REF_PTR,
expr.span,
"using `.clone()` on a ref-counted pointer",
"try this",
format!(
"{}::<{}>::clone(&{})",
caller_type,
subst.type_at(0),
snippet(cx, arg.span, "_")
),
Applicability::Unspecified, // Sometimes unnecessary ::<_> after Rc/Arc/Weak
);
}
}
fn lint_string_extend(cx: &LateContext<'_, '_>, expr: &hir::Expr<'_>, args: &[hir::Expr<'_>]) {
let arg = &args[1];
if let Some(arglists) = method_chain_args(arg, &["chars"]) {
let target = &arglists[0][0];
let self_ty = walk_ptrs_ty(cx.tables.expr_ty(target));
let ref_str = if self_ty.kind == ty::Str {
""
} else if match_type(cx, self_ty, &paths::STRING) {
"&"
} else {
return;
};
let mut applicability = Applicability::MachineApplicable;
span_lint_and_sugg(
cx,
STRING_EXTEND_CHARS,
expr.span,
"calling `.extend(_.chars())`",
"try this",
format!(
"{}.push_str({}{})",
snippet_with_applicability(cx, args[0].span, "_", &mut applicability),
ref_str,
snippet_with_applicability(cx, target.span, "_", &mut applicability)
),
applicability,
);
}
}
fn lint_extend(cx: &LateContext<'_, '_>, expr: &hir::Expr<'_>, args: &[hir::Expr<'_>]) {
let obj_ty = walk_ptrs_ty(cx.tables.expr_ty(&args[0]));
if match_type(cx, obj_ty, &paths::STRING) {
lint_string_extend(cx, expr, args);
}
}
fn lint_cstring_as_ptr(cx: &LateContext<'_, '_>, expr: &hir::Expr<'_>, source: &hir::Expr<'_>, unwrap: &hir::Expr<'_>) {
if_chain! {
let source_type = cx.tables.expr_ty(source);
if let ty::Adt(def, substs) = source_type.kind;
if match_def_path(cx, def.did, &paths::RESULT);
if match_type(cx, substs.type_at(0), &paths::CSTRING);
then {
span_lint_and_then(
cx,
TEMPORARY_CSTRING_AS_PTR,
expr.span,
"you are getting the inner pointer of a temporary `CString`",
|db| {
db.note("that pointer will be invalid outside this expression");
db.span_help(unwrap.span, "assign the `CString` to a variable to extend its lifetime");
});
}
}
}
fn lint_iter_cloned_collect<'a, 'tcx>(
cx: &LateContext<'a, 'tcx>,
expr: &hir::Expr<'_>,
iter_args: &'tcx [hir::Expr<'_>],
) {
if_chain! {
if is_type_diagnostic_item(cx, cx.tables.expr_ty(expr), Symbol::intern("vec_type"));
if let Some(slice) = derefs_to_slice(cx, &iter_args[0], cx.tables.expr_ty(&iter_args[0]));
if let Some(to_replace) = expr.span.trim_start(slice.span.source_callsite());
then {
span_lint_and_sugg(
cx,
ITER_CLONED_COLLECT,
to_replace,
"called `iter().cloned().collect()` on a slice to create a `Vec`. Calling `to_vec()` is both faster and \
more readable",
"try",
".to_vec()".to_string(),
Applicability::MachineApplicable,
);
}
}
}
fn lint_unnecessary_fold(cx: &LateContext<'_, '_>, expr: &hir::Expr<'_>, fold_args: &[hir::Expr<'_>], fold_span: Span) {
fn check_fold_with_op(
cx: &LateContext<'_, '_>,
expr: &hir::Expr<'_>,
fold_args: &[hir::Expr<'_>],
fold_span: Span,
op: hir::BinOpKind,
replacement_method_name: &str,
replacement_has_args: bool,
) {
if_chain! {
// Extract the body of the closure passed to fold
if let hir::ExprKind::Closure(_, _, body_id, _, _) = fold_args[2].kind;
let closure_body = cx.tcx.hir().body(body_id);
let closure_expr = remove_blocks(&closure_body.value);
// Check if the closure body is of the form `acc <op> some_expr(x)`
if let hir::ExprKind::Binary(ref bin_op, ref left_expr, ref right_expr) = closure_expr.kind;
if bin_op.node == op;
// Extract the names of the two arguments to the closure
if let Some(first_arg_ident) = get_arg_name(&closure_body.params[0].pat);
if let Some(second_arg_ident) = get_arg_name(&closure_body.params[1].pat);
if match_var(&*left_expr, first_arg_ident);
if replacement_has_args || match_var(&*right_expr, second_arg_ident);
then {
let mut applicability = Applicability::MachineApplicable;
let sugg = if replacement_has_args {
format!(
"{replacement}(|{s}| {r})",
replacement = replacement_method_name,
s = second_arg_ident,
r = snippet_with_applicability(cx, right_expr.span, "EXPR", &mut applicability),
)
} else {
format!(
"{replacement}()",
replacement = replacement_method_name,
)
};
span_lint_and_sugg(
cx,
UNNECESSARY_FOLD,
fold_span.with_hi(expr.span.hi()),
// TODO #2371 don't suggest e.g., .any(|x| f(x)) if we can suggest .any(f)
"this `.fold` can be written more succinctly using another method",
"try",
sugg,
applicability,
);
}
}
}
// Check that this is a call to Iterator::fold rather than just some function called fold
if !match_trait_method(cx, expr, &paths::ITERATOR) {
return;
}
assert!(
fold_args.len() == 3,
"Expected fold_args to have three entries - the receiver, the initial value and the closure"
);
// Check if the first argument to .fold is a suitable literal
if let hir::ExprKind::Lit(ref lit) = fold_args[1].kind {
match lit.node {
ast::LitKind::Bool(false) => {
check_fold_with_op(cx, expr, fold_args, fold_span, hir::BinOpKind::Or, "any", true)
},
ast::LitKind::Bool(true) => {
check_fold_with_op(cx, expr, fold_args, fold_span, hir::BinOpKind::And, "all", true)
},
ast::LitKind::Int(0, _) => {
check_fold_with_op(cx, expr, fold_args, fold_span, hir::BinOpKind::Add, "sum", false)
},
ast::LitKind::Int(1, _) => {
check_fold_with_op(cx, expr, fold_args, fold_span, hir::BinOpKind::Mul, "product", false)
},
_ => (),
}
}
}
fn lint_step_by<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &hir::Expr<'_>, args: &'tcx [hir::Expr<'_>]) {
if match_trait_method(cx, expr, &paths::ITERATOR) {
if let Some((Constant::Int(0), _)) = constant(cx, cx.tables, &args[1]) {
span_lint(
cx,
ITERATOR_STEP_BY_ZERO,
expr.span,
"Iterator::step_by(0) will panic at runtime",
);
}
}
}
fn lint_iter_nth<'a, 'tcx>(
cx: &LateContext<'a, 'tcx>,
expr: &hir::Expr<'_>,
nth_and_iter_args: &[&'tcx [hir::Expr<'tcx>]],
is_mut: bool,
) {
let iter_args = nth_and_iter_args[1];
let mut_str = if is_mut { "_mut" } else { "" };
let caller_type = if derefs_to_slice(cx, &iter_args[0], cx.tables.expr_ty(&iter_args[0])).is_some() {
"slice"
} else if is_type_diagnostic_item(cx, cx.tables.expr_ty(&iter_args[0]), Symbol::intern("vec_type")) {
"Vec"
} else if match_type(cx, cx.tables.expr_ty(&iter_args[0]), &paths::VEC_DEQUE) {
"VecDeque"
} else {
let nth_args = nth_and_iter_args[0];
lint_iter_nth_zero(cx, expr, &nth_args);
return; // caller is not a type that we want to lint
};
span_lint_and_help(
cx,
ITER_NTH,
expr.span,
&format!("called `.iter{0}().nth()` on a {1}", mut_str, caller_type),
&format!("calling `.get{}()` is both faster and more readable", mut_str),
);
}
fn lint_iter_nth_zero<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &hir::Expr<'_>, nth_args: &'tcx [hir::Expr<'_>]) {
if_chain! {
if match_trait_method(cx, expr, &paths::ITERATOR);
if let Some((Constant::Int(0), _)) = constant(cx, cx.tables, &nth_args[1]);
then {
let mut applicability = Applicability::MachineApplicable;
span_lint_and_sugg(
cx,
ITER_NTH_ZERO,
expr.span,
"called `.nth(0)` on a `std::iter::Iterator`",
"try calling",
format!("{}.next()", snippet_with_applicability(cx, nth_args[0].span, "..", &mut applicability)),
applicability,
);
}
}
}
fn lint_get_unwrap<'a, 'tcx>(
cx: &LateContext<'a, 'tcx>,
expr: &hir::Expr<'_>,
get_args: &'tcx [hir::Expr<'_>],
is_mut: bool,
) {
// Note: we don't want to lint `get_mut().unwrap` for `HashMap` or `BTreeMap`,
// because they do not implement `IndexMut`
let mut applicability = Applicability::MachineApplicable;
let expr_ty = cx.tables.expr_ty(&get_args[0]);
let get_args_str = if get_args.len() > 1 {
snippet_with_applicability(cx, get_args[1].span, "_", &mut applicability)
} else {
return; // not linting on a .get().unwrap() chain or variant
};
let mut needs_ref;
let caller_type = if derefs_to_slice(cx, &get_args[0], expr_ty).is_some() {
needs_ref = get_args_str.parse::<usize>().is_ok();
"slice"
} else if is_type_diagnostic_item(cx, expr_ty, Symbol::intern("vec_type")) {
needs_ref = get_args_str.parse::<usize>().is_ok();
"Vec"
} else if match_type(cx, expr_ty, &paths::VEC_DEQUE) {
needs_ref = get_args_str.parse::<usize>().is_ok();
"VecDeque"
} else if !is_mut && match_type(cx, expr_ty, &paths::HASHMAP) {
needs_ref = true;
"HashMap"
} else if !is_mut && match_type(cx, expr_ty, &paths::BTREEMAP) {
needs_ref = true;
"BTreeMap"
} else {
return; // caller is not a type that we want to lint
};
let mut span = expr.span;
// Handle the case where the result is immediately dereferenced
// by not requiring ref and pulling the dereference into the
// suggestion.
if_chain! {
if needs_ref;
if let Some(parent) = get_parent_expr(cx, expr);
if let hir::ExprKind::Unary(hir::UnOp::UnDeref, _) = parent.kind;
then {
needs_ref = false;
span = parent.span;
}
}
let mut_str = if is_mut { "_mut" } else { "" };
let borrow_str = if !needs_ref {
""
} else if is_mut {
"&mut "
} else {
"&"
};
span_lint_and_sugg(
cx,
GET_UNWRAP,
span,
&format!(
"called `.get{0}().unwrap()` on a {1}. Using `[]` is more clear and more concise",
mut_str, caller_type
),
"try this",
format!(
"{}{}[{}]",
borrow_str,
snippet_with_applicability(cx, get_args[0].span, "_", &mut applicability),
get_args_str
),
applicability,
);
}
fn lint_iter_skip_next(cx: &LateContext<'_, '_>, expr: &hir::Expr<'_>) {
// lint if caller of skip is an Iterator
if match_trait_method(cx, expr, &paths::ITERATOR) {
span_lint_and_help(
cx,
ITER_SKIP_NEXT,
expr.span,
"called `skip(x).next()` on an iterator",
"this is more succinctly expressed by calling `nth(x)`",
);
}
}
fn derefs_to_slice<'a, 'tcx>(
cx: &LateContext<'a, 'tcx>,
expr: &'tcx hir::Expr<'tcx>,
ty: Ty<'tcx>,
) -> Option<&'tcx hir::Expr<'tcx>> {
fn may_slice<'a>(cx: &LateContext<'_, 'a>, ty: Ty<'a>) -> bool {
match ty.kind {
ty::Slice(_) => true,
ty::Adt(def, _) if def.is_box() => may_slice(cx, ty.boxed_ty()),
ty::Adt(..) => is_type_diagnostic_item(cx, ty, Symbol::intern("vec_type")),
ty::Array(_, size) => {
if let Some(size) = size.try_eval_usize(cx.tcx, cx.param_env) {
size < 32
} else {
false
}
},
ty::Ref(_, inner, _) => may_slice(cx, inner),
_ => false,
}
}
if let hir::ExprKind::MethodCall(ref path, _, ref args) = expr.kind {
if path.ident.name == sym!(iter) && may_slice(cx, cx.tables.expr_ty(&args[0])) {
Some(&args[0])
} else {
None
}
} else {
match ty.kind {
ty::Slice(_) => Some(expr),
ty::Adt(def, _) if def.is_box() && may_slice(cx, ty.boxed_ty()) => Some(expr),
ty::Ref(_, inner, _) => {
if may_slice(cx, inner) {
Some(expr)
} else {
None
}
},
_ => None,
}
}
}
/// lint use of `unwrap()` for `Option`s and `Result`s
fn lint_unwrap(cx: &LateContext<'_, '_>, expr: &hir::Expr<'_>, unwrap_args: &[hir::Expr<'_>]) {
let obj_ty = walk_ptrs_ty(cx.tables.expr_ty(&unwrap_args[0]));
let mess = if match_type(cx, obj_ty, &paths::OPTION) {
Some((OPTION_UNWRAP_USED, "an Option", "None"))
} else if match_type(cx, obj_ty, &paths::RESULT) {
Some((RESULT_UNWRAP_USED, "a Result", "Err"))
} else {
None
};
if let Some((lint, kind, none_value)) = mess {
span_lint_and_help(
cx,
lint,
expr.span,
&format!("used `unwrap()` on `{}` value", kind,),
&format!(
"if you don't want to handle the `{}` case gracefully, consider \
using `expect()` to provide a better panic message",
none_value,
),
);
}
}
/// lint use of `expect()` for `Option`s and `Result`s
fn lint_expect(cx: &LateContext<'_, '_>, expr: &hir::Expr<'_>, expect_args: &[hir::Expr<'_>]) {
let obj_ty = walk_ptrs_ty(cx.tables.expr_ty(&expect_args[0]));
let mess = if match_type(cx, obj_ty, &paths::OPTION) {
Some((OPTION_EXPECT_USED, "an Option", "None"))
} else if match_type(cx, obj_ty, &paths::RESULT) {
Some((RESULT_EXPECT_USED, "a Result", "Err"))
} else {
None
};
if let Some((lint, kind, none_value)) = mess {
span_lint_and_help(
cx,
lint,
expr.span,
&format!("used `expect()` on `{}` value", kind,),
&format!("if this value is an `{}`, it will panic", none_value,),
);
}
}
/// lint use of `ok().expect()` for `Result`s
fn lint_ok_expect(cx: &LateContext<'_, '_>, expr: &hir::Expr<'_>, ok_args: &[hir::Expr<'_>]) {
if_chain! {
// lint if the caller of `ok()` is a `Result`
if match_type(cx, cx.tables.expr_ty(&ok_args[0]), &paths::RESULT);
let result_type = cx.tables.expr_ty(&ok_args[0]);
if let Some(error_type) = get_error_type(cx, result_type);
if has_debug_impl(error_type, cx);
then {
span_lint_and_help(
cx,
OK_EXPECT,
expr.span,
"called `ok().expect()` on a `Result` value",
"you can call `expect()` directly on the `Result`",
);
}
}
}
/// lint use of `map().flatten()` for `Iterators`
fn lint_map_flatten<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr<'_>, map_args: &'tcx [hir::Expr<'_>]) {
// lint if caller of `.map().flatten()` is an Iterator
if match_trait_method(cx, expr, &paths::ITERATOR) {
let msg = "called `map(..).flatten()` on an `Iterator`. \
This is more succinctly expressed by calling `.flat_map(..)`";
let self_snippet = snippet(cx, map_args[0].span, "..");
let func_snippet = snippet(cx, map_args[1].span, "..");
let hint = format!("{0}.flat_map({1})", self_snippet, func_snippet);
span_lint_and_sugg(
cx,
MAP_FLATTEN,
expr.span,
msg,
"try using `flat_map` instead",
hint,
Applicability::MachineApplicable,
);
}
}
/// lint use of `map().unwrap_or_else()` for `Option`s and `Result`s
fn lint_map_unwrap_or_else<'a, 'tcx>(
cx: &LateContext<'a, 'tcx>,
expr: &'tcx hir::Expr<'_>,
map_args: &'tcx [hir::Expr<'_>],
unwrap_args: &'tcx [hir::Expr<'_>],
) {
// lint if the caller of `map()` is an `Option`
let is_option = match_type(cx, cx.tables.expr_ty(&map_args[0]), &paths::OPTION);
let is_result = match_type(cx, cx.tables.expr_ty(&map_args[0]), &paths::RESULT);
if is_option || is_result {
// Don't make a suggestion that may fail to compile due to mutably borrowing
// the same variable twice.
let map_mutated_vars = mutated_variables(&map_args[0], cx);
let unwrap_mutated_vars = mutated_variables(&unwrap_args[1], cx);
if let (Some(map_mutated_vars), Some(unwrap_mutated_vars)) = (map_mutated_vars, unwrap_mutated_vars) {
if map_mutated_vars.intersection(&unwrap_mutated_vars).next().is_some() {
return;
}
} else {
return;
}
// lint message
let msg = if is_option {
"called `map(f).unwrap_or_else(g)` on an `Option` value. This can be done more directly by calling \
`map_or_else(g, f)` instead"
} else {
"called `map(f).unwrap_or_else(g)` on a `Result` value. This can be done more directly by calling \
`.map_or_else(g, f)` instead"
};
// get snippets for args to map() and unwrap_or_else()
let map_snippet = snippet(cx, map_args[1].span, "..");
let unwrap_snippet = snippet(cx, unwrap_args[1].span, "..");
// lint, with note if neither arg is > 1 line and both map() and
// unwrap_or_else() have the same span
let multiline = map_snippet.lines().count() > 1 || unwrap_snippet.lines().count() > 1;
let same_span = map_args[1].span.ctxt() == unwrap_args[1].span.ctxt();
if same_span && !multiline {
span_lint_and_note(
cx,
if is_option {
OPTION_MAP_UNWRAP_OR_ELSE
} else {
RESULT_MAP_UNWRAP_OR_ELSE
},
expr.span,
msg,
expr.span,
&format!(
"replace `map({0}).unwrap_or_else({1})` with `map_or_else({1}, {0})`",
map_snippet, unwrap_snippet,
),
);
} else if same_span && multiline {
span_lint(
cx,
if is_option {
OPTION_MAP_UNWRAP_OR_ELSE
} else {
RESULT_MAP_UNWRAP_OR_ELSE
},
expr.span,
msg,
);
};
}
}
/// lint use of `_.map_or(None, _)` for `Option`s
fn lint_map_or_none<'a, 'tcx>(
cx: &LateContext<'a, 'tcx>,
expr: &'tcx hir::Expr<'_>,
map_or_args: &'tcx [hir::Expr<'_>],
) {
if match_type(cx, cx.tables.expr_ty(&map_or_args[0]), &paths::OPTION) {
// check if the first non-self argument to map_or() is None
let map_or_arg_is_none = if let hir::ExprKind::Path(ref qpath) = map_or_args[1].kind {
match_qpath(qpath, &paths::OPTION_NONE)
} else {
false
};
if map_or_arg_is_none {
// lint message
let msg = "called `map_or(None, f)` on an `Option` value. This can be done more directly by calling \
`and_then(f)` instead";
let map_or_self_snippet = snippet(cx, map_or_args[0].span, "..");
let map_or_func_snippet = snippet(cx, map_or_args[2].span, "..");
let hint = format!("{0}.and_then({1})", map_or_self_snippet, map_or_func_snippet);
span_lint_and_sugg(
cx,
OPTION_MAP_OR_NONE,
expr.span,
msg,
"try using `and_then` instead",
hint,
Applicability::MachineApplicable,
);
}
}
}
/// Lint use of `_.and_then(|x| Some(y))` for `Option`s
fn lint_option_and_then_some(cx: &LateContext<'_, '_>, expr: &hir::Expr<'_>, args: &[hir::Expr<'_>]) {
const LINT_MSG: &str = "using `Option.and_then(|x| Some(y))`, which is more succinctly expressed as `map(|x| y)`";
const NO_OP_MSG: &str = "using `Option.and_then(Some)`, which is a no-op";
let ty = cx.tables.expr_ty(&args[0]);
if !match_type(cx, ty, &paths::OPTION) {
return;
}
match args[1].kind {
hir::ExprKind::Closure(_, _, body_id, closure_args_span, _) => {
let closure_body = cx.tcx.hir().body(body_id);
let closure_expr = remove_blocks(&closure_body.value);
if_chain! {
if let hir::ExprKind::Call(ref some_expr, ref some_args) = closure_expr.kind;
if let hir::ExprKind::Path(ref qpath) = some_expr.kind;
if match_qpath(qpath, &paths::OPTION_SOME);
if some_args.len() == 1;
then {
let inner_expr = &some_args[0];
if contains_return(inner_expr) {
return;
}
let some_inner_snip = if inner_expr.span.from_expansion() {
snippet_with_macro_callsite(cx, inner_expr.span, "_")
} else {
snippet(cx, inner_expr.span, "_")
};
let closure_args_snip = snippet(cx, closure_args_span, "..");
let option_snip = snippet(cx, args[0].span, "..");
let note = format!("{}.map({} {})", option_snip, closure_args_snip, some_inner_snip);
span_lint_and_sugg(
cx,
OPTION_AND_THEN_SOME,
expr.span,
LINT_MSG,
"try this",
note,
Applicability::MachineApplicable,
);
}
}
},
// `_.and_then(Some)` case, which is no-op.
hir::ExprKind::Path(ref qpath) => {
if match_qpath(qpath, &paths::OPTION_SOME) {
let option_snip = snippet(cx, args[0].span, "..");
let note = format!("{}", option_snip);
span_lint_and_sugg(
cx,
OPTION_AND_THEN_SOME,
expr.span,
NO_OP_MSG,
"use the expression directly",
note,
Applicability::MachineApplicable,
);
}
},
_ => {},
}
}
/// lint use of `filter().next()` for `Iterators`
fn lint_filter_next<'a, 'tcx>(
cx: &LateContext<'a, 'tcx>,
expr: &'tcx hir::Expr<'_>,
filter_args: &'tcx [hir::Expr<'_>],
) {
// lint if caller of `.filter().next()` is an Iterator
if match_trait_method(cx, expr, &paths::ITERATOR) {
let msg = "called `filter(p).next()` on an `Iterator`. This is more succinctly expressed by calling \
`.find(p)` instead.";
let filter_snippet = snippet(cx, filter_args[1].span, "..");
if filter_snippet.lines().count() <= 1 {
// add note if not multi-line
span_lint_and_note(
cx,
FILTER_NEXT,
expr.span,
msg,
expr.span,
&format!("replace `filter({0}).next()` with `find({0})`", filter_snippet),
);
} else {
span_lint(cx, FILTER_NEXT, expr.span, msg);
}
}
}
/// lint use of `skip_while().next()` for `Iterators`
fn lint_skip_while_next<'a, 'tcx>(
cx: &LateContext<'a, 'tcx>,
expr: &'tcx hir::Expr<'_>,
_skip_while_args: &'tcx [hir::Expr<'_>],
) {
// lint if caller of `.skip_while().next()` is an Iterator
if match_trait_method(cx, expr, &paths::ITERATOR) {
span_lint_and_help(
cx,
SKIP_WHILE_NEXT,
expr.span,
"called `skip_while(p).next()` on an `Iterator`",
"this is more succinctly expressed by calling `.find(!p)` instead",
);
}
}
/// lint use of `filter().map()` for `Iterators`
fn lint_filter_map<'a, 'tcx>(
cx: &LateContext<'a, 'tcx>,
expr: &'tcx hir::Expr<'_>,
_filter_args: &'tcx [hir::Expr<'_>],
_map_args: &'tcx [hir::Expr<'_>],
) {
// lint if caller of `.filter().map()` is an Iterator
if match_trait_method(cx, expr, &paths::ITERATOR) {
let msg = "called `filter(p).map(q)` on an `Iterator`";
let hint = "this is more succinctly expressed by calling `.filter_map(..)` instead";
span_lint_and_help(cx, FILTER_MAP, expr.span, msg, hint);
}
}
/// lint use of `filter_map().next()` for `Iterators`
fn lint_filter_map_next<'a, 'tcx>(
cx: &LateContext<'a, 'tcx>,
expr: &'tcx hir::Expr<'_>,
filter_args: &'tcx [hir::Expr<'_>],
) {
if match_trait_method(cx, expr, &paths::ITERATOR) {
let msg = "called `filter_map(p).next()` on an `Iterator`. This is more succinctly expressed by calling \
`.find_map(p)` instead.";
let filter_snippet = snippet(cx, filter_args[1].span, "..");
if filter_snippet.lines().count() <= 1 {
span_lint_and_note(
cx,
FILTER_MAP_NEXT,
expr.span,
msg,
expr.span,
&format!("replace `filter_map({0}).next()` with `find_map({0})`", filter_snippet),
);
} else {
span_lint(cx, FILTER_MAP_NEXT, expr.span, msg);
}
}
}
/// lint use of `find().map()` for `Iterators`
fn lint_find_map<'a, 'tcx>(
cx: &LateContext<'a, 'tcx>,
expr: &'tcx hir::Expr<'_>,
_find_args: &'tcx [hir::Expr<'_>],
map_args: &'tcx [hir::Expr<'_>],
) {
// lint if caller of `.filter().map()` is an Iterator
if match_trait_method(cx, &map_args[0], &paths::ITERATOR) {
let msg = "called `find(p).map(q)` on an `Iterator`";
let hint = "this is more succinctly expressed by calling `.find_map(..)` instead";
span_lint_and_help(cx, FIND_MAP, expr.span, msg, hint);
}
}
/// lint use of `filter_map().map()` for `Iterators`
fn lint_filter_map_map<'a, 'tcx>(
cx: &LateContext<'a, 'tcx>,
expr: &'tcx hir::Expr<'_>,
_filter_args: &'tcx [hir::Expr<'_>],
_map_args: &'tcx [hir::Expr<'_>],
) {
// lint if caller of `.filter().map()` is an Iterator
if match_trait_method(cx, expr, &paths::ITERATOR) {
let msg = "called `filter_map(p).map(q)` on an `Iterator`";
let hint = "this is more succinctly expressed by only calling `.filter_map(..)` instead";
span_lint_and_help(cx, FILTER_MAP, expr.span, msg, hint);
}
}
/// lint use of `filter().flat_map()` for `Iterators`
fn lint_filter_flat_map<'a, 'tcx>(
cx: &LateContext<'a, 'tcx>,
expr: &'tcx hir::Expr<'_>,
_filter_args: &'tcx [hir::Expr<'_>],
_map_args: &'tcx [hir::Expr<'_>],
) {
// lint if caller of `.filter().flat_map()` is an Iterator
if match_trait_method(cx, expr, &paths::ITERATOR) {
let msg = "called `filter(p).flat_map(q)` on an `Iterator`";
let hint = "this is more succinctly expressed by calling `.flat_map(..)` \
and filtering by returning `iter::empty()`";
span_lint_and_help(cx, FILTER_MAP, expr.span, msg, hint);
}
}
/// lint use of `filter_map().flat_map()` for `Iterators`
fn lint_filter_map_flat_map<'a, 'tcx>(
cx: &LateContext<'a, 'tcx>,
expr: &'tcx hir::Expr<'_>,
_filter_args: &'tcx [hir::Expr<'_>],
_map_args: &'tcx [hir::Expr<'_>],
) {
// lint if caller of `.filter_map().flat_map()` is an Iterator
if match_trait_method(cx, expr, &paths::ITERATOR) {
let msg = "called `filter_map(p).flat_map(q)` on an `Iterator`";
let hint = "this is more succinctly expressed by calling `.flat_map(..)` \
and filtering by returning `iter::empty()`";
span_lint_and_help(cx, FILTER_MAP, expr.span, msg, hint);
}
}
/// lint use of `flat_map` for `Iterators` where `flatten` would be sufficient
fn lint_flat_map_identity<'a, 'tcx>(
cx: &LateContext<'a, 'tcx>,
expr: &'tcx hir::Expr<'_>,
flat_map_args: &'tcx [hir::Expr<'_>],
flat_map_span: Span,
) {
if match_trait_method(cx, expr, &paths::ITERATOR) {
let arg_node = &flat_map_args[1].kind;
let apply_lint = |message: &str| {
span_lint_and_sugg(
cx,
FLAT_MAP_IDENTITY,
flat_map_span.with_hi(expr.span.hi()),
message,
"try",
"flatten()".to_string(),
Applicability::MachineApplicable,
);
};
if_chain! {
if let hir::ExprKind::Closure(_, _, body_id, _, _) = arg_node;
let body = cx.tcx.hir().body(*body_id);
if let hir::PatKind::Binding(_, _, binding_ident, _) = body.params[0].pat.kind;
if let hir::ExprKind::Path(hir::QPath::Resolved(_, ref path)) = body.value.kind;
if path.segments.len() == 1;
if path.segments[0].ident.as_str() == binding_ident.as_str();
then {
apply_lint("called `flat_map(|x| x)` on an `Iterator`");
}
}
if_chain! {
if let hir::ExprKind::Path(ref qpath) = arg_node;
if match_qpath(qpath, &paths::STD_CONVERT_IDENTITY);
then {
apply_lint("called `flat_map(std::convert::identity)` on an `Iterator`");
}
}
}
}
/// lint searching an Iterator followed by `is_some()`
fn lint_search_is_some<'a, 'tcx>(
cx: &LateContext<'a, 'tcx>,
expr: &'tcx hir::Expr<'_>,
search_method: &str,
search_args: &'tcx [hir::Expr<'_>],
is_some_args: &'tcx [hir::Expr<'_>],
method_span: Span,
) {
// lint if caller of search is an Iterator
if match_trait_method(cx, &is_some_args[0], &paths::ITERATOR) {
let msg = format!(
"called `is_some()` after searching an `Iterator` with {}. This is more succinctly \
expressed by calling `any()`.",
search_method
);
let search_snippet = snippet(cx, search_args[1].span, "..");
if search_snippet.lines().count() <= 1 {
// suggest `any(|x| ..)` instead of `any(|&x| ..)` for `find(|&x| ..).is_some()`
// suggest `any(|..| *..)` instead of `any(|..| **..)` for `find(|..| **..).is_some()`
let any_search_snippet = if_chain! {
if search_method == "find";
if let hir::ExprKind::Closure(_, _, body_id, ..) = search_args[1].kind;
let closure_body = cx.tcx.hir().body(body_id);
if let Some(closure_arg) = closure_body.params.get(0);
then {
if let hir::PatKind::Ref(..) = closure_arg.pat.kind {
Some(search_snippet.replacen('&', "", 1))
} else if let Some(name) = get_arg_name(&closure_arg.pat) {
Some(search_snippet.replace(&format!("*{}", name), &name.as_str()))
} else {
None
}
} else {
None
}
};
// add note if not multi-line
span_lint_and_sugg(
cx,
SEARCH_IS_SOME,
method_span.with_hi(expr.span.hi()),
&msg,
"try this",
format!(
"any({})",
any_search_snippet.as_ref().map_or(&*search_snippet, String::as_str)
),
Applicability::MachineApplicable,
);
} else {
span_lint(cx, SEARCH_IS_SOME, expr.span, &msg);
}
}
}
/// 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:ident, $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!(lint_chars_next_cmp, cx, info);
lint_with_both_lhs_and_rhs!(lint_chars_last_cmp, cx, info);
lint_with_both_lhs_and_rhs!(lint_chars_next_cmp_with_unwrap, cx, info);
lint_with_both_lhs_and_rhs!(lint_chars_last_cmp_with_unwrap, cx, info);
}
/// Wrapper fn for `CHARS_NEXT_CMP` and `CHARS_LAST_CMP` lints.
fn lint_chars_cmp(
cx: &LateContext<'_, '_>,
info: &BinaryExprInfo<'_>,
chain_methods: &[&str],
lint: &'static Lint,
suggest: &str,
) -> bool {
if_chain! {
if let Some(args) = method_chain_args(info.chain, chain_methods);
if let hir::ExprKind::Call(ref fun, ref arg_char) = info.other.kind;
if arg_char.len() == 1;
if let hir::ExprKind::Path(ref qpath) = fun.kind;
if let Some(segment) = single_segment_path(qpath);
if segment.ident.name == sym!(Some);
then {
let mut applicability = Applicability::MachineApplicable;
let self_ty = walk_ptrs_ty(cx.tables.expr_ty_adjusted(&args[0][0]));
if self_ty.kind != ty::Str {
return false;
}
span_lint_and_sugg(
cx,
lint,
info.expr.span,
&format!("you should use the `{}` method", suggest),
"like this",
format!("{}{}.{}({})",
if info.eq { "" } else { "!" },
snippet_with_applicability(cx, args[0][0].span, "_", &mut applicability),
suggest,
snippet_with_applicability(cx, arg_char[0].span, "_", &mut applicability)),
applicability,
);
return true;
}
}
false
}
/// Checks for the `CHARS_NEXT_CMP` lint.
fn lint_chars_next_cmp<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, info: &BinaryExprInfo<'_>) -> bool {
lint_chars_cmp(cx, info, &["chars", "next"], CHARS_NEXT_CMP, "starts_with")
}
/// Checks for the `CHARS_LAST_CMP` lint.
fn lint_chars_last_cmp<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, info: &BinaryExprInfo<'_>) -> bool {
if lint_chars_cmp(cx, info, &["chars", "last"], CHARS_LAST_CMP, "ends_with") {
true
} else {
lint_chars_cmp(cx, info, &["chars", "next_back"], CHARS_LAST_CMP, "ends_with")
}
}
/// Wrapper fn for `CHARS_NEXT_CMP` and `CHARS_LAST_CMP` lints with `unwrap()`.
fn lint_chars_cmp_with_unwrap<'a, 'tcx>(
cx: &LateContext<'a, 'tcx>,
info: &BinaryExprInfo<'_>,
chain_methods: &[&str],
lint: &'static Lint,
suggest: &str,
) -> bool {
if_chain! {
if let Some(args) = method_chain_args(info.chain, chain_methods);
if let hir::ExprKind::Lit(ref lit) = info.other.kind;
if let ast::LitKind::Char(c) = lit.node;
then {
let mut applicability = Applicability::MachineApplicable;
span_lint_and_sugg(
cx,
lint,
info.expr.span,
&format!("you should use the `{}` method", suggest),
"like this",
format!("{}{}.{}('{}')",
if info.eq { "" } else { "!" },
snippet_with_applicability(cx, args[0][0].span, "_", &mut applicability),
suggest,
c),
applicability,
);
true
} else {
false
}
}
}
/// Checks for the `CHARS_NEXT_CMP` lint with `unwrap()`.
fn lint_chars_next_cmp_with_unwrap<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, info: &BinaryExprInfo<'_>) -> bool {
lint_chars_cmp_with_unwrap(cx, info, &["chars", "next", "unwrap"], CHARS_NEXT_CMP, "starts_with")
}
/// Checks for the `CHARS_LAST_CMP` lint with `unwrap()`.
fn lint_chars_last_cmp_with_unwrap<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, info: &BinaryExprInfo<'_>) -> bool {
if lint_chars_cmp_with_unwrap(cx, info, &["chars", "last", "unwrap"], CHARS_LAST_CMP, "ends_with") {
true
} else {
lint_chars_cmp_with_unwrap(cx, info, &["chars", "next_back", "unwrap"], CHARS_LAST_CMP, "ends_with")
}
}
/// lint for length-1 `str`s for methods in `PATTERN_METHODS`
fn lint_single_char_pattern<'a, 'tcx>(
cx: &LateContext<'a, 'tcx>,
_expr: &'tcx hir::Expr<'_>,
arg: &'tcx hir::Expr<'_>,
) {
if_chain! {
if let hir::ExprKind::Lit(lit) = &arg.kind;
if let ast::LitKind::Str(r, style) = lit.node;
if r.as_str().len() == 1;
then {
let mut applicability = Applicability::MachineApplicable;
let snip = snippet_with_applicability(cx, arg.span, "..", &mut 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 });
span_lint_and_sugg(
cx,
SINGLE_CHAR_PATTERN,
arg.span,
"single-character string constant used as pattern",
"try using a `char` instead",
hint,
applicability,
);
}
}
}
/// Checks for the `USELESS_ASREF` lint.
fn lint_asref(cx: &LateContext<'_, '_>, expr: &hir::Expr<'_>, call_name: &str, as_ref_args: &[hir::Expr<'_>]) {
// when we get here, we've already checked that the call name is "as_ref" or "as_mut"
// check if the call is to the actual `AsRef` or `AsMut` trait
if match_trait_method(cx, expr, &paths::ASREF_TRAIT) || match_trait_method(cx, expr, &paths::ASMUT_TRAIT) {
// check if the type after `as_ref` or `as_mut` is the same as before
let recvr = &as_ref_args[0];
let rcv_ty = cx.tables.expr_ty(recvr);
let res_ty = cx.tables.expr_ty(expr);
let (base_res_ty, res_depth) = walk_ptrs_ty_depth(res_ty);
let (base_rcv_ty, rcv_depth) = walk_ptrs_ty_depth(rcv_ty);
if base_rcv_ty == base_res_ty && rcv_depth >= res_depth {
// allow the `as_ref` or `as_mut` if it is followed by another method call
if_chain! {
if let Some(parent) = get_parent_expr(cx, expr);
if let hir::ExprKind::MethodCall(_, ref span, _) = parent.kind;
if span != &expr.span;
then {
return;
}
}
let mut applicability = Applicability::MachineApplicable;
span_lint_and_sugg(
cx,
USELESS_ASREF,
expr.span,
&format!("this call to `{}` does nothing", call_name),
"try this",
snippet_with_applicability(cx, recvr.span, "_", &mut applicability).to_string(),
applicability,
);
}
}
}
fn ty_has_iter_method(cx: &LateContext<'_, '_>, self_ref_ty: Ty<'_>) -> Option<(&'static str, &'static str)> {
has_iter_method(cx, self_ref_ty).map(|ty_name| {
let mutbl = match self_ref_ty.kind {
ty::Ref(_, _, mutbl) => mutbl,
_ => unreachable!(),
};
let method_name = match mutbl {
hir::Mutability::Not => "iter",
hir::Mutability::Mut => "iter_mut",
};
(ty_name, method_name)
})
}
fn lint_into_iter(cx: &LateContext<'_, '_>, expr: &hir::Expr<'_>, self_ref_ty: Ty<'_>, method_span: Span) {
if !match_trait_method(cx, expr, &paths::INTO_ITERATOR) {
return;
}
if let Some((kind, method_name)) = ty_has_iter_method(cx, self_ref_ty) {
span_lint_and_sugg(
cx,
INTO_ITER_ON_REF,
method_span,
&format!(
"this `.into_iter()` call is equivalent to `.{}()` and will not move the `{}`",
method_name, kind,
),
"call directly",
method_name.to_string(),
Applicability::MachineApplicable,
);
}
}
/// lint for `MaybeUninit::uninit().assume_init()` (we already have the latter)
fn lint_maybe_uninit(cx: &LateContext<'_, '_>, expr: &hir::Expr<'_>, outer: &hir::Expr<'_>) {
if_chain! {
if let hir::ExprKind::Call(ref callee, ref args) = expr.kind;
if args.is_empty();
if let hir::ExprKind::Path(ref path) = callee.kind;
if match_qpath(path, &paths::MEM_MAYBEUNINIT_UNINIT);
if !is_maybe_uninit_ty_valid(cx, cx.tables.expr_ty_adjusted(outer));
then {
span_lint(
cx,
UNINIT_ASSUMED_INIT,
outer.span,
"this call for this type may be undefined behavior"
);
}
}
}
fn is_maybe_uninit_ty_valid(cx: &LateContext<'_, '_>, ty: Ty<'_>) -> bool {
match ty.kind {
ty::Array(ref component, _) => is_maybe_uninit_ty_valid(cx, component),
ty::Tuple(ref types) => types.types().all(|ty| is_maybe_uninit_ty_valid(cx, ty)),
ty::Adt(ref adt, _) => {
// needs to be a MaybeUninit
match_def_path(cx, adt.did, &paths::MEM_MAYBEUNINIT)
},
_ => false,
}
}
fn lint_suspicious_map(cx: &LateContext<'_, '_>, expr: &hir::Expr<'_>) {
span_lint_and_help(
cx,
SUSPICIOUS_MAP,
expr.span,
"this call to `map()` won't have an effect on the call to `count()`",
"make sure you did not confuse `map` with `filter` or `for_each`",
);
}
/// lint use of `_.as_ref().map(Deref::deref)` for `Option`s
fn lint_option_as_ref_deref<'a, 'tcx>(
cx: &LateContext<'a, 'tcx>,
expr: &hir::Expr<'_>,
as_ref_args: &[hir::Expr<'_>],
map_args: &[hir::Expr<'_>],
is_mut: bool,
) {
let option_ty = cx.tables.expr_ty(&as_ref_args[0]);
if !match_type(cx, option_ty, &paths::OPTION) {
return;
}
let deref_aliases: [&[&str]; 9] = [
&paths::DEREF_TRAIT_METHOD,
&paths::DEREF_MUT_TRAIT_METHOD,
&paths::CSTRING_AS_C_STR,
&paths::OS_STRING_AS_OS_STR,
&paths::PATH_BUF_AS_PATH,
&paths::STRING_AS_STR,
&paths::STRING_AS_MUT_STR,
&paths::VEC_AS_SLICE,
&paths::VEC_AS_MUT_SLICE,
];
let is_deref = match map_args[1].kind {
hir::ExprKind::Path(ref expr_qpath) => deref_aliases.iter().any(|path| match_qpath(expr_qpath, path)),
hir::ExprKind::Closure(_, _, body_id, _, _) => {
let closure_body = cx.tcx.hir().body(body_id);
let closure_expr = remove_blocks(&closure_body.value);
if_chain! {
if let hir::ExprKind::MethodCall(_, _, args) = &closure_expr.kind;
if args.len() == 1;
if let hir::ExprKind::Path(qpath) = &args[0].kind;
if let hir::def::Res::Local(local_id) = cx.tables.qpath_res(qpath, args[0].hir_id);
if closure_body.params[0].pat.hir_id == local_id;
let adj = cx.tables.expr_adjustments(&args[0]).iter().map(|x| &x.kind).collect::<Box<[_]>>();
if let [ty::adjustment::Adjust::Deref(None), ty::adjustment::Adjust::Borrow(_)] = *adj;
then {
let method_did = cx.tables.type_dependent_def_id(closure_expr.hir_id).unwrap();
deref_aliases.iter().any(|path| match_def_path(cx, method_did, path))
} else {
false
}
}
},
_ => false,
};
if is_deref {
let current_method = if is_mut {
".as_mut().map(DerefMut::deref_mut)"
} else {
".as_ref().map(Deref::deref)"
};
let method_hint = if is_mut { "as_deref_mut" } else { "as_deref" };
let hint = format!("{}.{}()", snippet(cx, as_ref_args[0].span, ".."), method_hint);
let suggestion = format!("try using {} instead", method_hint);
let msg = format!(
"called `{0}` (or with one of deref aliases) on an Option value. \
This can be done more directly by calling `{1}` instead",
current_method, hint
);
span_lint_and_sugg(
cx,
OPTION_AS_REF_DEREF,
expr.span,
&msg,
&suggestion,
hint,
Applicability::MachineApplicable,
);
}
}
/// Given a `Result<T, E>` type, return its error type (`E`).
fn get_error_type<'a>(cx: &LateContext<'_, '_>, ty: Ty<'a>) -> Option<Ty<'a>> {
match ty.kind {
ty::Adt(_, substs) if match_type(cx, ty, &paths::RESULT) => substs.types().nth(1),
_ => None,
}
}
/// This checks whether a given type is known to implement Debug.
fn has_debug_impl<'a, 'b>(ty: Ty<'a>, cx: &LateContext<'b, 'a>) -> bool {
cx.tcx
.get_diagnostic_item(sym::debug_trait)
.map_or(false, |debug| implements_trait(cx, ty, debug, &[]))
}
enum Convention {
Eq(&'static str),
StartsWith(&'static str),
}
#[rustfmt::skip]
const CONVENTIONS: [(Convention, &[SelfKind]); 7] = [
(Convention::Eq("new"), &[SelfKind::No]),
(Convention::StartsWith("as_"), &[SelfKind::Ref, SelfKind::RefMut]),
(Convention::StartsWith("from_"), &[SelfKind::No]),
(Convention::StartsWith("into_"), &[SelfKind::Value]),
(Convention::StartsWith("is_"), &[SelfKind::Ref, SelfKind::No]),
(Convention::Eq("to_mut"), &[SelfKind::RefMut]),
(Convention::StartsWith("to_"), &[SelfKind::Ref]),
];
#[rustfmt::skip]
const TRAIT_METHODS: [(&str, usize, SelfKind, OutType, &str); 30] = [
("add", 2, SelfKind::Value, OutType::Any, "std::ops::Add"),
("as_mut", 1, SelfKind::RefMut, OutType::Ref, "std::convert::AsMut"),
("as_ref", 1, SelfKind::Ref, OutType::Ref, "std::convert::AsRef"),
("bitand", 2, SelfKind::Value, OutType::Any, "std::ops::BitAnd"),
("bitor", 2, SelfKind::Value, OutType::Any, "std::ops::BitOr"),
("bitxor", 2, SelfKind::Value, OutType::Any, "std::ops::BitXor"),
("borrow", 1, SelfKind::Ref, OutType::Ref, "std::borrow::Borrow"),
("borrow_mut", 1, SelfKind::RefMut, OutType::Ref, "std::borrow::BorrowMut"),
("clone", 1, SelfKind::Ref, OutType::Any, "std::clone::Clone"),
("cmp", 2, SelfKind::Ref, OutType::Any, "std::cmp::Ord"),
("default", 0, SelfKind::No, OutType::Any, "std::default::Default"),
("deref", 1, SelfKind::Ref, OutType::Ref, "std::ops::Deref"),
("deref_mut", 1, SelfKind::RefMut, OutType::Ref, "std::ops::DerefMut"),
("div", 2, SelfKind::Value, OutType::Any, "std::ops::Div"),
("drop", 1, SelfKind::RefMut, OutType::Unit, "std::ops::Drop"),
("eq", 2, SelfKind::Ref, OutType::Bool, "std::cmp::PartialEq"),
("from_iter", 1, SelfKind::No, OutType::Any, "std::iter::FromIterator"),
("from_str", 1, SelfKind::No, OutType::Any, "std::str::FromStr"),
("hash", 2, SelfKind::Ref, OutType::Unit, "std::hash::Hash"),
("index", 2, SelfKind::Ref, OutType::Ref, "std::ops::Index"),
("index_mut", 2, SelfKind::RefMut, OutType::Ref, "std::ops::IndexMut"),
("into_iter", 1, SelfKind::Value, OutType::Any, "std::iter::IntoIterator"),
("mul", 2, SelfKind::Value, OutType::Any, "std::ops::Mul"),
("neg", 1, SelfKind::Value, OutType::Any, "std::ops::Neg"),
("next", 1, SelfKind::RefMut, OutType::Any, "std::iter::Iterator"),
("not", 1, SelfKind::Value, OutType::Any, "std::ops::Not"),
("rem", 2, SelfKind::Value, OutType::Any, "std::ops::Rem"),
("shl", 2, SelfKind::Value, OutType::Any, "std::ops::Shl"),
("shr", 2, SelfKind::Value, OutType::Any, "std::ops::Shr"),
("sub", 2, SelfKind::Value, OutType::Any, "std::ops::Sub"),
];
#[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(parent_ty: Ty<'_>, ty: Ty<'_>) -> bool {
if ty == parent_ty {
true
} else if ty.is_box() {
ty.boxed_ty() == parent_ty
} else if ty.is_rc() || ty.is_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(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",
}
}
}
impl Convention {
#[must_use]
fn check(&self, other: &str) -> bool {
match *self {
Self::Eq(this) => this == other,
Self::StartsWith(this) => other.starts_with(this) && this != other,
}
}
}
impl fmt::Display for Convention {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
match *self {
Self::Eq(this) => this.fmt(f),
Self::StartsWith(this) => this.fmt(f).and_then(|_| '*'.fmt(f)),
}
}
}
#[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
}
}
// Returns `true` if `expr` contains a return expression
fn contains_return(expr: &hir::Expr<'_>) -> bool {
struct RetCallFinder {
found: bool,
}
impl<'tcx> intravisit::Visitor<'tcx> for RetCallFinder {
type Map = Map<'tcx>;
fn visit_expr(&mut self, expr: &'tcx hir::Expr<'_>) {
if self.found {
return;
}
if let hir::ExprKind::Ret(..) = &expr.kind {
self.found = true;
} else {
intravisit::walk_expr(self, expr);
}
}
fn nested_visit_map(&mut self) -> intravisit::NestedVisitorMap<'_, Self::Map> {
intravisit::NestedVisitorMap::None
}
}
let mut visitor = RetCallFinder { found: false };
visitor.visit_expr(expr);
visitor.found
}
fn check_pointer_offset(cx: &LateContext<'_, '_>, expr: &hir::Expr<'_>, args: &[hir::Expr<'_>]) {
if_chain! {
if args.len() == 2;
if let ty::RawPtr(ty::TypeAndMut { ref ty, .. }) = cx.tables.expr_ty(&args[0]).kind;
if let Ok(layout) = cx.tcx.layout_of(cx.param_env.and(ty));
if layout.is_zst();
then {
span_lint(cx, ZST_OFFSET, expr.span, "offset calculation on zero-sized value");
}
}
}
fn lint_filetype_is_file(cx: &LateContext<'_, '_>, expr: &hir::Expr<'_>, args: &[hir::Expr<'_>]) {
let ty = cx.tables.expr_ty(&args[0]);
if !match_type(cx, ty, &paths::FILE_TYPE) {
return;
}
let span: Span;
let verb: &str;
let lint_unary: &str;
let help_unary: &str;
if_chain! {
if let Some(parent) = get_parent_expr(cx, expr);
if let hir::ExprKind::Unary(op, _) = parent.kind;
if op == hir::UnOp::UnNot;
then {
lint_unary = "!";
verb = "denies";
help_unary = "";
span = parent.span;
} else {
lint_unary = "";
verb = "covers";
help_unary = "!";
span = expr.span;
}
}
let lint_msg = format!("`{}FileType::is_file()` only {} regular files", lint_unary, verb);
let help_msg = format!("use `{}FileType::is_dir()` instead", help_unary);
span_lint_and_help(cx, FILETYPE_IS_FILE, span, &lint_msg, &help_msg);
}