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 #[clippy::version = "pre 1.29.0"]
30 pub TOO_MANY_ARGUMENTS,
32 "functions with too many arguments"
35 declare_clippy_lint! {
37 /// Checks for functions with a large amount of lines.
39 /// ### Why is this bad?
40 /// Functions with a lot of lines are harder to understand
41 /// due to having to look at a larger amount of code to understand what the
42 /// function is doing. Consider splitting the body of the function into
43 /// multiple functions.
47 /// fn im_too_long() {
49 /// // ... 100 more LoC
53 #[clippy::version = "1.34.0"]
56 "functions with too many lines"
59 declare_clippy_lint! {
61 /// Checks for public functions that dereference raw pointer
62 /// arguments but are not marked `unsafe`.
64 /// ### Why is this bad?
65 /// The function should probably be marked `unsafe`, since
66 /// for an arbitrary raw pointer, there is no way of telling for sure if it is
69 /// ### Known problems
70 /// * It does not check functions recursively so if the pointer is passed to a
71 /// private non-`unsafe` function which does the dereferencing, the lint won't
73 /// * It only checks for arguments whose type are raw pointers, not raw pointers
74 /// got from an argument in some other way (`fn foo(bar: &[*const u8])` or
75 /// `some_argument.get_raw_ptr()`).
79 /// pub fn foo(x: *const u8) {
80 /// println!("{}", unsafe { *x });
86 /// pub unsafe fn foo(x: *const u8) {
87 /// println!("{}", unsafe { *x });
90 #[clippy::version = "pre 1.29.0"]
91 pub NOT_UNSAFE_PTR_ARG_DEREF,
93 "public functions dereferencing raw pointer arguments but not marked `unsafe`"
96 declare_clippy_lint! {
98 /// Checks for a `#[must_use]` attribute on
99 /// unit-returning functions and methods.
101 /// ### Why is this bad?
102 /// Unit values are useless. The attribute is likely
103 /// a remnant of a refactoring that removed the return type.
110 #[clippy::version = "1.40.0"]
113 "`#[must_use]` attribute on a unit-returning function / method"
116 declare_clippy_lint! {
118 /// Checks for a `#[must_use]` attribute without
119 /// further information on functions and methods that return a type already
120 /// marked as `#[must_use]`.
122 /// ### Why is this bad?
123 /// The attribute isn't needed. Not using the result
124 /// will already be reported. Alternatively, one can add some text to the
125 /// attribute to improve the lint message.
130 /// fn double_must_use() -> Result<(), ()> {
131 /// unimplemented!();
134 #[clippy::version = "1.40.0"]
137 "`#[must_use]` attribute on a `#[must_use]`-returning function / method"
140 declare_clippy_lint! {
142 /// Checks for public functions that have no
143 /// `#[must_use]` attribute, but return something not already marked
144 /// must-use, have no mutable arg and mutate no statics.
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 #[clippy::version = "1.40.0"]
165 pub MUST_USE_CANDIDATE,
167 "function or method that could take a `#[must_use]` attribute"
170 declare_clippy_lint! {
172 /// Checks for public functions that return a `Result`
173 /// with an `Err` type of `()`. It suggests using a custom type that
174 /// implements `std::error::Error`.
176 /// ### Why is this bad?
177 /// Unit does not implement `Error` and carries no
178 /// further information about what went wrong.
180 /// ### Known problems
181 /// Of course, this lint assumes that `Result` is used
182 /// for a fallible operation (which is after all the intended use). However
183 /// code may opt to (mis)use it as a basic two-variant-enum. In that case,
184 /// the suggestion is misguided, and the code should use a custom enum
189 /// pub fn read_u8() -> Result<u8, ()> { Err(()) }
192 /// ```rust,should_panic
196 /// pub struct EndOfStream;
198 /// impl fmt::Display for EndOfStream {
199 /// fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
200 /// write!(f, "End of Stream")
204 /// impl std::error::Error for EndOfStream { }
206 /// pub fn read_u8() -> Result<u8, EndOfStream> { Err(EndOfStream) }
208 ///# read_u8().unwrap();
212 /// Note that there are crates that simplify creating the error type, e.g.
213 /// [`thiserror`](https://docs.rs/thiserror).
214 #[clippy::version = "1.49.0"]
217 "public function returning `Result` with an `Err` type of `()`"
220 #[derive(Copy, Clone)]
221 pub struct Functions {
222 too_many_arguments_threshold: u64,
223 too_many_lines_threshold: u64,
227 pub fn new(too_many_arguments_threshold: u64, too_many_lines_threshold: u64) -> Self {
229 too_many_arguments_threshold,
230 too_many_lines_threshold,
235 impl_lint_pass!(Functions => [
238 NOT_UNSAFE_PTR_ARG_DEREF,
245 impl<'tcx> LateLintPass<'tcx> for Functions {
248 cx: &LateContext<'tcx>,
249 kind: intravisit::FnKind<'tcx>,
250 decl: &'tcx hir::FnDecl<'_>,
251 body: &'tcx hir::Body<'_>,
255 too_many_arguments::check_fn(cx, kind, decl, span, hir_id, self.too_many_arguments_threshold);
256 too_many_lines::check_fn(cx, kind, span, body, self.too_many_lines_threshold);
257 not_unsafe_ptr_arg_deref::check_fn(cx, kind, decl, body, hir_id);
260 fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'_>) {
261 must_use::check_item(cx, item);
262 result_unit_err::check_item(cx, item);
265 fn check_impl_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::ImplItem<'_>) {
266 must_use::check_impl_item(cx, item);
267 result_unit_err::check_impl_item(cx, item);
270 fn check_trait_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::TraitItem<'_>) {
271 too_many_arguments::check_trait_item(cx, item, self.too_many_arguments_threshold);
272 not_unsafe_ptr_arg_deref::check_trait_item(cx, item);
273 must_use::check_trait_item(cx, item);
274 result_unit_err::check_trait_item(cx, item);