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 /// ### Why is this bad?
98 /// Unit values are useless. The attribute is likely
99 /// a remnant of a refactoring that removed the return type.
108 "`#[must_use]` attribute on a unit-returning function / method"
111 declare_clippy_lint! {
113 /// Checks for a `#[must_use]` attribute without
114 /// further information on functions and methods that return a type already
115 /// marked as `#[must_use]`.
117 /// ### Why is this bad?
118 /// The attribute isn't needed. Not using the result
119 /// will already be reported. Alternatively, one can add some text to the
120 /// attribute to improve the lint message.
125 /// fn double_must_use() -> Result<(), ()> {
126 /// unimplemented!();
131 "`#[must_use]` attribute on a `#[must_use]`-returning function / method"
134 declare_clippy_lint! {
136 /// Checks for public functions that have no
137 /// `#[must_use]` attribute, but return something not already marked
138 /// must-use, have no mutable arg and mutate no statics.
140 /// ### Why is this bad?
141 /// Not bad at all, this lint just shows places where
142 /// you could add the attribute.
144 /// ### Known problems
145 /// The lint only checks the arguments for mutable
146 /// types without looking if they are actually changed. On the other hand,
147 /// it also ignores a broad range of potentially interesting side effects,
148 /// because we cannot decide whether the programmer intends the function to
149 /// be called for the side effect or the result. Expect many false
150 /// positives. At least we don't lint if the result type is unit or already
155 /// // this could be annotated with `#[must_use]`.
156 /// fn id<T>(t: T) -> T { t }
158 pub MUST_USE_CANDIDATE,
160 "function or method that could take a `#[must_use]` attribute"
163 declare_clippy_lint! {
165 /// Checks for public functions that return a `Result`
166 /// with an `Err` type of `()`. It suggests using a custom type that
167 /// implements `std::error::Error`.
169 /// ### Why is this bad?
170 /// Unit does not implement `Error` and carries no
171 /// further information about what went wrong.
173 /// ### Known problems
174 /// Of course, this lint assumes that `Result` is used
175 /// for a fallible operation (which is after all the intended use). However
176 /// code may opt to (mis)use it as a basic two-variant-enum. In that case,
177 /// the suggestion is misguided, and the code should use a custom enum
182 /// pub fn read_u8() -> Result<u8, ()> { Err(()) }
185 /// ```rust,should_panic
189 /// pub struct EndOfStream;
191 /// impl fmt::Display for EndOfStream {
192 /// fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
193 /// write!(f, "End of Stream")
197 /// impl std::error::Error for EndOfStream { }
199 /// pub fn read_u8() -> Result<u8, EndOfStream> { Err(EndOfStream) }
201 ///# read_u8().unwrap();
205 /// Note that there are crates that simplify creating the error type, e.g.
206 /// [`thiserror`](https://docs.rs/thiserror).
209 "public function returning `Result` with an `Err` type of `()`"
212 #[derive(Copy, Clone)]
213 pub struct Functions {
214 too_many_arguments_threshold: u64,
215 too_many_lines_threshold: u64,
219 pub fn new(too_many_arguments_threshold: u64, too_many_lines_threshold: u64) -> Self {
221 too_many_arguments_threshold,
222 too_many_lines_threshold,
227 impl_lint_pass!(Functions => [
230 NOT_UNSAFE_PTR_ARG_DEREF,
237 impl<'tcx> LateLintPass<'tcx> for Functions {
240 cx: &LateContext<'tcx>,
241 kind: intravisit::FnKind<'tcx>,
242 decl: &'tcx hir::FnDecl<'_>,
243 body: &'tcx hir::Body<'_>,
247 too_many_arguments::check_fn(cx, kind, decl, span, hir_id, self.too_many_arguments_threshold);
248 too_many_lines::check_fn(cx, kind, span, body, self.too_many_lines_threshold);
249 not_unsafe_ptr_arg_deref::check_fn(cx, kind, decl, body, hir_id);
252 fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'_>) {
253 must_use::check_item(cx, item);
254 result_unit_err::check_item(cx, item);
257 fn check_impl_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::ImplItem<'_>) {
258 must_use::check_impl_item(cx, item);
259 result_unit_err::check_impl_item(cx, item);
262 fn check_trait_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::TraitItem<'_>) {
263 too_many_arguments::check_trait_item(cx, item, self.too_many_arguments_threshold);
264 not_unsafe_ptr_arg_deref::check_trait_item(cx, item);
265 must_use::check_trait_item(cx, item);
266 result_unit_err::check_trait_item(cx, item);