2 mod not_unsafe_ptr_arg_deref;
4 mod too_many_arguments;
8 use rustc_hir::intravisit;
9 use rustc_lint::{LateContext, LateLintPass};
10 use rustc_session::{declare_tool_lint, impl_lint_pass};
13 declare_clippy_lint! {
15 /// Checks for functions with too many parameters.
17 /// ### Why is this bad?
18 /// Functions with lots of parameters are considered bad
19 /// style and reduce readability (“what does the 5th parameter mean?”). Consider
20 /// grouping some parameters into a new type.
25 /// fn foo(x: u32, y: u32, name: &str, c: Color, w: f32, h: f32, a: f32, b: f32) {
29 pub TOO_MANY_ARGUMENTS,
31 "functions with too many arguments"
34 declare_clippy_lint! {
36 /// Checks for functions with a large amount of lines.
38 /// ### Why is this bad?
39 /// Functions with a lot of lines are harder to understand
40 /// due to having to look at a larger amount of code to understand what the
41 /// function is doing. Consider splitting the body of the function into
42 /// multiple functions.
46 /// fn im_too_long() {
48 /// // ... 100 more LoC
54 "functions with too many lines"
57 declare_clippy_lint! {
59 /// Checks for public functions that dereference raw pointer
60 /// arguments but are not marked `unsafe`.
62 /// ### Why is this bad?
63 /// The function should probably be marked `unsafe`, since
64 /// for an arbitrary raw pointer, there is no way of telling for sure if it is
67 /// ### Known problems
68 /// * It does not check functions recursively so if the pointer is passed to a
69 /// private non-`unsafe` function which does the dereferencing, the lint won't
71 /// * It only checks for arguments whose type are raw pointers, not raw pointers
72 /// got from an argument in some other way (`fn foo(bar: &[*const u8])` or
73 /// `some_argument.get_raw_ptr()`).
78 /// pub fn foo(x: *const u8) {
79 /// println!("{}", unsafe { *x });
83 /// pub unsafe fn foo(x: *const u8) {
84 /// println!("{}", unsafe { *x });
87 pub NOT_UNSAFE_PTR_ARG_DEREF,
89 "public functions dereferencing raw pointer arguments but not marked `unsafe`"
92 declare_clippy_lint! {
94 /// Checks for a [`#[must_use]`] attribute on
95 /// unit-returning functions and methods.
97 /// [`#[must_use]`]: https://doc.rust-lang.org/reference/attributes/diagnostics.html#the-must_use-attribute
99 /// ### Why is this bad?
100 /// Unit values are useless. The attribute is likely
101 /// a remnant of a refactoring that removed the return type.
110 "`#[must_use]` attribute on a unit-returning function / method"
113 declare_clippy_lint! {
115 /// Checks for a [`#[must_use]`] attribute without
116 /// further information on functions and methods that return a type already
117 /// marked as `#[must_use]`.
119 /// [`#[must_use]`]: https://doc.rust-lang.org/reference/attributes/diagnostics.html#the-must_use-attribute
121 /// ### Why is this bad?
122 /// The attribute isn't needed. Not using the result
123 /// will already be reported. Alternatively, one can add some text to the
124 /// attribute to improve the lint message.
129 /// fn double_must_use() -> Result<(), ()> {
130 /// unimplemented!();
135 "`#[must_use]` attribute on a `#[must_use]`-returning function / method"
138 declare_clippy_lint! {
140 /// Checks for public functions that have no
141 /// [`#[must_use]`] attribute, but return something not already marked
142 /// must-use, have no mutable arg and mutate no statics.
144 /// [`#[must_use]`]: https://doc.rust-lang.org/reference/attributes/diagnostics.html#the-must_use-attribute
146 /// ### Why is this bad?
147 /// Not bad at all, this lint just shows places where
148 /// you could add the attribute.
150 /// ### Known problems
151 /// The lint only checks the arguments for mutable
152 /// types without looking if they are actually changed. On the other hand,
153 /// it also ignores a broad range of potentially interesting side effects,
154 /// because we cannot decide whether the programmer intends the function to
155 /// be called for the side effect or the result. Expect many false
156 /// positives. At least we don't lint if the result type is unit or already
161 /// // this could be annotated with `#[must_use]`.
162 /// fn id<T>(t: T) -> T { t }
164 pub MUST_USE_CANDIDATE,
166 "function or method that could take a `#[must_use]` attribute"
169 declare_clippy_lint! {
171 /// Checks for public functions that return a `Result`
172 /// with an `Err` type of `()`. It suggests using a custom type that
173 /// implements `std::error::Error`.
175 /// ### Why is this bad?
176 /// Unit does not implement `Error` and carries no
177 /// further information about what went wrong.
179 /// ### Known problems
180 /// Of course, this lint assumes that `Result` is used
181 /// for a fallible operation (which is after all the intended use). However
182 /// code may opt to (mis)use it as a basic two-variant-enum. In that case,
183 /// the suggestion is misguided, and the code should use a custom enum
188 /// pub fn read_u8() -> Result<u8, ()> { Err(()) }
191 /// ```rust,should_panic
195 /// pub struct EndOfStream;
197 /// impl fmt::Display for EndOfStream {
198 /// fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
199 /// write!(f, "End of Stream")
203 /// impl std::error::Error for EndOfStream { }
205 /// pub fn read_u8() -> Result<u8, EndOfStream> { Err(EndOfStream) }
207 ///# read_u8().unwrap();
211 /// Note that there are crates that simplify creating the error type, e.g.
212 /// [`thiserror`](https://docs.rs/thiserror).
215 "public function returning `Result` with an `Err` type of `()`"
218 #[derive(Copy, Clone)]
219 pub struct Functions {
220 too_many_arguments_threshold: u64,
221 too_many_lines_threshold: u64,
225 pub fn new(too_many_arguments_threshold: u64, too_many_lines_threshold: u64) -> Self {
227 too_many_arguments_threshold,
228 too_many_lines_threshold,
233 impl_lint_pass!(Functions => [
236 NOT_UNSAFE_PTR_ARG_DEREF,
243 impl<'tcx> LateLintPass<'tcx> for Functions {
246 cx: &LateContext<'tcx>,
247 kind: intravisit::FnKind<'tcx>,
248 decl: &'tcx hir::FnDecl<'_>,
249 body: &'tcx hir::Body<'_>,
253 too_many_arguments::check_fn(cx, kind, decl, span, hir_id, self.too_many_arguments_threshold);
254 too_many_lines::check_fn(cx, kind, span, body, self.too_many_lines_threshold);
255 not_unsafe_ptr_arg_deref::check_fn(cx, kind, decl, body, hir_id);
258 fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'_>) {
259 must_use::check_item(cx, item);
260 result_unit_err::check_item(cx, item);
263 fn check_impl_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::ImplItem<'_>) {
264 must_use::check_impl_item(cx, item);
265 result_unit_err::check_impl_item(cx, item);
268 fn check_trait_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::TraitItem<'_>) {
269 too_many_arguments::check_trait_item(cx, item, self.too_many_arguments_threshold);
270 not_unsafe_ptr_arg_deref::check_trait_item(cx, item);
271 must_use::check_trait_item(cx, item);
272 result_unit_err::check_trait_item(cx, item);