1 #![warn(clippy::needless_lifetimes)]
2 #![allow(dead_code, clippy::needless_pass_by_value, clippy::unnecessary_wraps, dyn_drop)]
4 fn distinct_lifetimes<'a, 'b>(_x: &'a u8, _y: &'b u8, _z: u8) {}
6 fn distinct_and_static<'a, 'b>(_x: &'a u8, _y: &'b u8, _z: &'static u8) {}
8 // No error; same lifetime on two params.
9 fn same_lifetime_on_input<'a>(_x: &'a u8, _y: &'a u8) {}
11 // No error; static involved.
12 fn only_static_on_input(_x: &u8, _y: &u8, _z: &'static u8) {}
14 fn mut_and_static_input(_x: &mut u8, _y: &'static str) {}
16 fn in_and_out<'a>(x: &'a u8, _y: u8) -> &'a u8 {
20 // No error; multiple input refs.
21 fn multiple_in_and_out_1<'a>(x: &'a u8, _y: &'a u8) -> &'a u8 {
25 // No error; multiple input refs.
26 fn multiple_in_and_out_2<'a, 'b>(x: &'a u8, _y: &'b u8) -> &'a u8 {
30 // No error; multiple input refs
31 async fn func<'a>(args: &[&'a str]) -> Option<&'a str> {
35 // No error; static involved.
36 fn in_static_and_out<'a>(x: &'a u8, _y: &'static u8) -> &'a u8 {
41 fn deep_reference_1<'a, 'b>(x: &'a u8, _y: &'b u8) -> Result<&'a u8, ()> {
45 // No error; two input refs.
46 fn deep_reference_2<'a>(x: Result<&'a u8, &'a u8>) -> &'a u8 {
50 fn deep_reference_3<'a>(x: &'a u8, _y: u8) -> Result<&'a u8, ()> {
54 // Where-clause, but without lifetimes.
55 fn where_clause_without_lt<'a, T>(x: &'a u8, _y: u8) -> Result<&'a u8, ()>
62 type Ref<'r> = &'r u8;
64 // No error; same lifetime on two params.
65 fn lifetime_param_1<'a>(_x: Ref<'a>, _y: &'a u8) {}
67 fn lifetime_param_2<'a, 'b>(_x: Ref<'a>, _y: &'b u8) {}
69 // No error; bounded lifetime.
70 fn lifetime_param_3<'a, 'b: 'a>(_x: Ref<'a>, _y: &'b u8) {}
72 // No error; bounded lifetime.
73 fn lifetime_param_4<'a, 'b>(_x: Ref<'a>, _y: &'b u8)
79 struct Lt<'a, I: 'static> {
83 // No error; fn bound references `'a`.
84 fn fn_bound<'a, F, I>(_m: Lt<'a, I>, _f: F) -> Lt<'a, I>
86 F: Fn(Lt<'a, I>) -> Lt<'a, I>,
91 fn fn_bound_2<'a, F, I>(_m: Lt<'a, I>, _f: F) -> Lt<'a, I>
93 for<'x> F: Fn(Lt<'x, I>) -> Lt<'x, I>,
98 // No error; see below.
99 fn fn_bound_3<'a, F: FnOnce(&'a i32)>(x: &'a i32, f: F) {
103 fn fn_bound_3_cannot_elide() {
107 // This will fail if we elide lifetimes of `fn_bound_3`.
108 fn_bound_3(p, |y| q = y);
111 // No error; multiple input refs.
112 fn fn_bound_4<'a, F: FnOnce() -> &'a ()>(cond: bool, x: &'a (), f: F) -> &'a () {
113 if cond { x } else { f() }
121 fn self_and_out<'s>(&'s self) -> &'s u8 {
125 // No error; multiple input refs.
126 fn self_and_in_out<'s, 't>(&'s self, _x: &'t u8) -> &'s u8 {
130 fn distinct_self_and_in<'s, 't>(&'s self, _x: &'t u8) {}
132 // No error; same lifetimes on two params.
133 fn self_and_same_in<'s>(&'s self, _x: &'s u8) {}
136 struct Foo<'a>(&'a u8);
139 // No error; lifetime `'a` not defined in method.
140 fn self_shared_lifetime(&self, _: &'a u8) {}
141 // No error; bounds exist.
142 fn self_bound_lifetime<'b: 'a>(&self, _: &'b u8) {}
145 fn already_elided<'a>(_: &u8, _: &'a u8) -> &'a u8 {
149 fn struct_with_lt<'a>(_foo: Foo<'a>) -> &'a str {
153 // No warning; two input lifetimes (named on the reference, anonymous on `Foo`).
154 fn struct_with_lt2<'a>(_foo: &'a Foo) -> &'a str {
158 // No warning; two input lifetimes (anonymous on the reference, named on `Foo`).
159 fn struct_with_lt3<'a>(_foo: &Foo<'a>) -> &'a str {
163 // No warning; two input lifetimes.
164 fn struct_with_lt4<'a, 'b>(_foo: &'a Foo<'b>) -> &'a str {
168 trait WithLifetime<'a> {}
170 type WithLifetimeAlias<'a> = dyn WithLifetime<'a>;
172 // Should not warn because it won't build without the lifetime.
173 fn trait_obj_elided<'a>(_arg: &'a dyn WithLifetime) -> &'a str {
177 // Should warn because there is no lifetime on `Drop`, so this would be
178 // unambiguous if we elided the lifetime.
179 fn trait_obj_elided2<'a>(_arg: &'a dyn Drop) -> &'a str {
183 type FooAlias<'a> = Foo<'a>;
185 fn alias_with_lt<'a>(_foo: FooAlias<'a>) -> &'a str {
189 // No warning; two input lifetimes (named on the reference, anonymous on `FooAlias`).
190 fn alias_with_lt2<'a>(_foo: &'a FooAlias) -> &'a str {
194 // No warning; two input lifetimes (anonymous on the reference, named on `FooAlias`).
195 fn alias_with_lt3<'a>(_foo: &FooAlias<'a>) -> &'a str {
199 // No warning; two input lifetimes.
200 fn alias_with_lt4<'a, 'b>(_foo: &'a FooAlias<'b>) -> &'a str {
204 fn named_input_elided_output<'a>(_arg: &'a str) -> &str {
208 fn elided_input_named_output<'a>(_arg: &str) -> &'a str {
212 fn trait_bound_ok<'a, T: WithLifetime<'static>>(_: &'a u8, _: T) {
215 fn trait_bound<'a, T: WithLifetime<'a>>(_: &'a u8, _: T) {
219 // Don't warn on these; see issue #292.
220 fn trait_bound_bug<'a, T: WithLifetime<'a>>() {
230 fn iter<'a>(&'a self) -> Box<dyn Iterator<Item = usize> + 'a> {
235 trait LintContext<'a> {}
237 fn f<'a, T: LintContext<'a>>(_: &T) {}
239 fn test<'a>(x: &'a [u8]) -> u8 {
240 let y: &'a u8 = &x[5];
244 // Issue #3284: give hint regarding lifetime in return type.
248 fn out_return_type_lts<'a>(e: &'a str) -> Cow<'a> {
252 // Make sure we still warn on implementations
255 fn needless_lt<'a>(x: &'a u8) {}
258 impl BadTrait for () {
259 fn needless_lt<'a>(_x: &'a u8) {}
270 impl<'a> Foo for Baz<'a> {}
272 fn baz<'a>(&'a self) -> impl Foo + 'a {
278 mod nested_elision_sites {
281 // closure trait bounds subject to nested elision
282 // don't lint because they refer to outer lifetimes
283 fn trait_fn<'a>(i: &'a i32) -> impl Fn() -> &'a i32 {
286 fn trait_fn_mut<'a>(i: &'a i32) -> impl FnMut() -> &'a i32 {
289 fn trait_fn_once<'a>(i: &'a i32) -> impl FnOnce() -> &'a i32 {
294 fn impl_trait_in_input_position<'a>(f: impl Fn() -> &'a i32) -> &'a i32 {
297 fn impl_trait_in_output_position<'a>(i: &'a i32) -> impl Fn() -> &'a i32 {
301 fn impl_trait_elidable_nested_named_lifetimes<'a>(i: &'a i32, f: impl for<'b> Fn(&'b i32) -> &'b i32) -> &'a i32 {
304 fn impl_trait_elidable_nested_anonymous_lifetimes<'a>(i: &'a i32, f: impl Fn(&i32) -> &i32) -> &'a i32 {
309 fn generics_not_elidable<'a, T: Fn() -> &'a i32>(f: T) -> &'a i32 {
313 fn generics_elidable<'a, T: Fn(&i32) -> &i32>(i: &'a i32, f: T) -> &'a i32 {
318 fn where_clause_not_elidable<'a, T>(f: T) -> &'a i32
325 fn where_clause_elidadable<'a, T>(i: &'a i32, f: T) -> &'a i32
333 fn pointer_fn_in_input_position<'a>(f: fn(&'a i32) -> &'a i32, i: &'a i32) -> &'a i32 {
336 fn pointer_fn_in_output_position<'a>(_: &'a i32) -> fn(&'a i32) -> &'a i32 {
340 fn pointer_fn_elidable<'a>(i: &'a i32, f: fn(&i32) -> &i32) -> &'a i32 {
345 fn nested_fn_pointer_1<'a>(_: &'a i32) -> fn(fn(&'a i32) -> &'a i32) -> i32 {
348 fn nested_fn_pointer_2<'a>(_: &'a i32) -> impl Fn(fn(&'a i32)) {
353 fn nested_fn_pointer_3<'a>(_: &'a i32) -> fn(fn(&i32) -> &i32) -> i32 {
356 fn nested_fn_pointer_4<'a>(_: &'a i32) -> impl Fn(fn(&i32)) {
363 pub fn apply_deref<'a, T, F, R>(x: &'a T, f: F) -> R
366 F: FnOnce(&'a T::Target) -> R,