From 1ef32e4096bb813edee300a5fa89c355959ed878 Mon Sep 17 00:00:00 2001
From: Rotem Yaari <vmalloc@gmail.com>
Date: Mon, 8 Oct 2018 11:43:13 +0300
Subject: [PATCH] Improve diagnostics in case of lifetime elision (closes
#3284)
---
clippy_lints/src/lifetimes.rs | 2 +-
tests/ui/lifetimes.rs | 6 ++++++
tests/ui/lifetimes.stderr | 36 ++++++++++++++++++++---------------
3 files changed, 28 insertions(+), 16 deletions(-)
diff --git a/clippy_lints/src/lifetimes.rs b/clippy_lints/src/lifetimes.rs
index d1cf0da876b..81d37404d77 100644
--- a/clippy_lints/src/lifetimes.rs
+++ b/clippy_lints/src/lifetimes.rs
@@ -152,7 +152,7 @@ fn check_fn_inner<'a, 'tcx>(
cx,
NEEDLESS_LIFETIMES,
span,
- "explicit lifetimes given in parameter types where they could be elided",
+ "explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)",
);
}
report_extra_lifetimes(cx, decl, generics);
diff --git a/tests/ui/lifetimes.rs b/tests/ui/lifetimes.rs
index cae18498779..c7ed303b43b 100644
--- a/tests/ui/lifetimes.rs
+++ b/tests/ui/lifetimes.rs
@@ -170,5 +170,11 @@ fn test<'a>(x: &'a [u8]) -> u8 {
*y
}
+// #3284 - Give a hint regarding lifetime in return type
+
+struct Cow<'a> { x: &'a str, }
+fn out_return_type_lts<'a>(e: &'a str) -> Cow<'a> { unimplemented!() }
+
+
fn main() {
}
diff --git a/tests/ui/lifetimes.stderr b/tests/ui/lifetimes.stderr
index 9e4fac1e4f2..46dbf6cce09 100644
--- a/tests/ui/lifetimes.stderr
+++ b/tests/ui/lifetimes.stderr
@@ -1,4 +1,4 @@
-error: explicit lifetimes given in parameter types where they could be elided
+error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
--> $DIR/lifetimes.rs:17:1
|
17 | fn distinct_lifetimes<'a, 'b>(_x: &'a u8, _y: &'b u8, _z: u8) { }
@@ -6,37 +6,37 @@ error: explicit lifetimes given in parameter types where they could be elided
|
= note: `-D clippy::needless-lifetimes` implied by `-D warnings`
-error: explicit lifetimes given in parameter types where they could be elided
+error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
--> $DIR/lifetimes.rs:19:1
|
19 | 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
+error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
--> $DIR/lifetimes.rs:27:1
|
27 | fn in_and_out<'a>(x: &'a u8, _y: u8) -> &'a u8 { x }
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-error: explicit lifetimes given in parameter types where they could be elided
+error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
--> $DIR/lifetimes.rs:39:1
|
39 | fn deep_reference_3<'a>(x: &'a u8, _y: u8) -> Result<&'a u8, ()> { Ok(x) }
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-error: explicit lifetimes given in parameter types where they could be elided
+error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
--> $DIR/lifetimes.rs:42:1
|
42 | fn where_clause_without_lt<'a, T>(x: &'a u8, _y: u8) -> Result<&'a u8, ()> where T: Copy { Ok(x) }
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-error: explicit lifetimes given in parameter types where they could be elided
+error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
--> $DIR/lifetimes.rs:48:1
|
48 | fn lifetime_param_2<'a, 'b>(_x: Ref<'a>, _y: &'b u8) { }
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-error: explicit lifetimes given in parameter types where they could be elided
+error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
--> $DIR/lifetimes.rs:62:1
|
62 | / fn fn_bound_2<'a, F, I>(_m: Lt<'a, I>, _f: F) -> Lt<'a, I>
@@ -44,47 +44,53 @@ error: explicit lifetimes given in parameter types where they could be elided
64 | | { unreachable!() }
| |__________________^
-error: explicit lifetimes given in parameter types where they could be elided
+error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
--> $DIR/lifetimes.rs:87:5
|
87 | fn self_and_out<'s>(&'s self) -> &'s u8 { &self.x }
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-error: explicit lifetimes given in parameter types where they could be elided
+error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
--> $DIR/lifetimes.rs:91:5
|
91 | fn distinct_self_and_in<'s, 't>(&'s self, _x: &'t u8) { }
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-error: explicit lifetimes given in parameter types where they could be elided
+error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
--> $DIR/lifetimes.rs:107:1
|
107 | fn struct_with_lt<'a>(_foo: Foo<'a>) -> &'a str { unimplemented!() }
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-error: explicit lifetimes given in parameter types where they could be elided
+error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
--> $DIR/lifetimes.rs:127:1
|
127 | fn trait_obj_elided2<'a>(_arg: &'a Drop) -> &'a str { unimplemented!() }
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-error: explicit lifetimes given in parameter types where they could be elided
+error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
--> $DIR/lifetimes.rs:131:1
|
131 | fn alias_with_lt<'a>(_foo: FooAlias<'a>) -> &'a str { unimplemented!() }
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-error: explicit lifetimes given in parameter types where they could be elided
+error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
--> $DIR/lifetimes.rs:142:1
|
142 | fn named_input_elided_output<'a>(_arg: &'a str) -> &str { unimplemented!() }
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-error: explicit lifetimes given in parameter types where they could be elided
+error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
--> $DIR/lifetimes.rs:146:1
|
146 | fn trait_bound_ok<'a, T: WithLifetime<'static>>(_: &'a u8, _: T) { unimplemented!() }
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-error: aborting due to 14 previous errors
+error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
+ --> $DIR/lifetimes.rs:176:1
+ |
+176 | fn out_return_type_lts<'a>(e: &'a str) -> Cow<'a> { unimplemented!() }
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 15 previous errors