Improvement: Don't show function body in needless_lifetimes

Changes the span on which the lint is reported to point to only the
function return type instead of the entire function body.
Fixes #5284

clippy_lints/src/lifetimes.rs

@@ -169,7 +169,7 @@ fn check_fn_inner<'a, 'tcx>(
  span_lint(
  cx,
  NEEDLESS_LIFETIMES,
- span,
+ span.with_hi(decl.output.span().hi()),
  "explicit lifetimes given in parameter types where they could be elided \
  (or replaced with `'_` if needed by type declaration)",
  );

tests/ui/issue_4266.stderr

@@ -2,17 +2,15 @@ error: explicit lifetimes given in parameter types where they could be elided (o
  --> $DIR/issue_4266.rs:4:1
  |
 LL | async fn sink1<'a>(_: &'a str) {} // lint
- | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = note: `-D clippy::needless-lifetimes` implied by `-D warnings`
 
 error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
  --> $DIR/issue_4266.rs:8:1
  |
-LL | / async fn one_to_one<'a>(s: &'a str) -> &'a str {
-LL | | s
-LL | | }
- | |_^
+LL | async fn one_to_one<'a>(s: &'a str) -> &'a str {
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: aborting due to 2 previous errors
 

tests/ui/needless_lifetimes.stderr

@@ -2,133 +2,105 @@ error: explicit lifetimes given in parameter types where they could be elided (o
  --> $DIR/needless_lifetimes.rs:4:1
  |
 LL | fn distinct_lifetimes<'a, 'b>(_x: &'a u8, _y: &'b u8, _z: u8) {}
- | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = note: `-D clippy::needless-lifetimes` implied by `-D warnings`
 
 error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
  --> $DIR/needless_lifetimes.rs:6:1
  |
 LL | fn distinct_and_static<'a, 'b>(_x: &'a u8, _y: &'b u8, _z: &'static u8) {}
- | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
  --> $DIR/needless_lifetimes.rs:16:1
  |
-LL | / fn in_and_out<'a>(x: &'a u8, _y: u8) -> &'a u8 {
-LL | | x
-LL | | }
- | |_^
+LL | fn in_and_out<'a>(x: &'a u8, _y: u8) -> &'a u8 {
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
  --> $DIR/needless_lifetimes.rs:45:1
  |
-LL | / fn deep_reference_3<'a>(x: &'a u8, _y: u8) -> Result<&'a u8, ()> {
-LL | | Ok(x)
-LL | | }
- | |_^
+LL | fn deep_reference_3<'a>(x: &'a u8, _y: u8) -> Result<&'a u8, ()> {
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
  --> $DIR/needless_lifetimes.rs:50:1
  |
-LL | / fn where_clause_without_lt<'a, T>(x: &'a u8, _y: u8) -> Result<&'a u8, ()>
-LL | | where
-LL | | T: Copy,
-LL | | {
-LL | | Ok(x)
-LL | | }
- | |_^
+LL | fn where_clause_without_lt<'a, T>(x: &'a u8, _y: u8) -> Result<&'a u8, ()>
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
  --> $DIR/needless_lifetimes.rs:62:1
  |
 LL | fn lifetime_param_2<'a, 'b>(_x: Ref<'a>, _y: &'b u8) {}
- | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
  --> $DIR/needless_lifetimes.rs:86:1
  |
-LL | / fn fn_bound_2<'a, F, I>(_m: Lt<'a, I>, _f: F) -> Lt<'a, I>
-LL | | where
-LL | | for<'x> F: Fn(Lt<'x, I>) -> Lt<'x, I>,
-LL | | {
-LL | | unreachable!()
-LL | | }
- | |_^
+LL | fn fn_bound_2<'a, F, I>(_m: Lt<'a, I>, _f: F) -> Lt<'a, I>
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
  --> $DIR/needless_lifetimes.rs:120:5
  |
-LL | / fn self_and_out<'s>(&'s self) -> &'s u8 {
-LL | | &self.x
-LL | | }
- | |_____^
+LL | fn self_and_out<'s>(&'s self) -> &'s u8 {
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
  --> $DIR/needless_lifetimes.rs:129:5
  |
 LL | fn distinct_self_and_in<'s, 't>(&'s self, _x: &'t u8) {}
- | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
  --> $DIR/needless_lifetimes.rs:148:1
  |
-LL | / fn struct_with_lt<'a>(_foo: Foo<'a>) -> &'a str {
-LL | | unimplemented!()
-LL | | }
- | |_^
+LL | fn struct_with_lt<'a>(_foo: Foo<'a>) -> &'a str {
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
  --> $DIR/needless_lifetimes.rs:178:1
  |
-LL | / fn trait_obj_elided2<'a>(_arg: &'a dyn Drop) -> &'a str {
-LL | | unimplemented!()
-LL | | }
- | |_^
+LL | fn trait_obj_elided2<'a>(_arg: &'a dyn Drop) -> &'a str {
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
  --> $DIR/needless_lifetimes.rs:184:1
  |
-LL | / fn alias_with_lt<'a>(_foo: FooAlias<'a>) -> &'a str {
-LL | | unimplemented!()
-LL | | }
- | |_^
+LL | fn alias_with_lt<'a>(_foo: FooAlias<'a>) -> &'a str {
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
  --> $DIR/needless_lifetimes.rs:203:1
  |
-LL | / fn named_input_elided_output<'a>(_arg: &'a str) -> &str {
-LL | | unimplemented!()
-LL | | }
- | |_^
+LL | fn named_input_elided_output<'a>(_arg: &'a str) -> &str {
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
  --> $DIR/needless_lifetimes.rs:211:1
  |
-LL | / fn trait_bound_ok<'a, T: WithLifetime<'static>>(_: &'a u8, _: T) {
-LL | | unimplemented!()
-LL | | }
- | |_^
+LL | fn trait_bound_ok<'a, T: WithLifetime<'static>>(_: &'a u8, _: T) {
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
  --> $DIR/needless_lifetimes.rs:247:1
  |
-LL | / fn out_return_type_lts<'a>(e: &'a str) -> Cow<'a> {
-LL | | unimplemented!()
-LL | | }
- | |_^
+LL | fn out_return_type_lts<'a>(e: &'a str) -> Cow<'a> {
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
  --> $DIR/needless_lifetimes.rs:254:9
  |
 LL | fn needless_lt<'a>(x: &'a u8) {}
- | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
  --> $DIR/needless_lifetimes.rs:258:9
  |
 LL | fn needless_lt<'a>(_x: &'a u8) {}
- | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: aborting due to 17 previous errors