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Rollup merge of #108230 - LittleFall:enhance/warning, r=estebank

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Convert a hard-warning about named static lifetimes into lint "unused_lifetimes"

Fixes https://github.com/rust-lang/rust/issues/96956.

Some changes are ported from https://github.com/rust-lang/rust/pull/98079, thanks to jeremydavis519.

r? `@estebank` `@petrochenkov`

Any feedback is appreciated!

## Actions
- [x] resolve conflicts
- [x] fix build
- [x] address review comments in last pr
- [x] update tests
This commit is contained in:
Guillaume Gomez 2023-02-22 10:35:08 +01:00 committed by GitHub
commit a32c500400
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GPG Key ID: 4AEE18F83AFDEB23
21 changed files with 97 additions and 122 deletions
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46
compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs
View File

@ -18,6 +18,7 @@ use rustc_middle::bug;
use rustc_middle::hir::nested_filter;
use rustc_middle::middle::resolve_bound_vars::*;
use rustc_middle::ty::{self, ir::TypeVisitor, DefIdTree, TyCtxt, TypeSuperVisitable};
use rustc_session::lint;
use rustc_span::def_id::DefId;
use rustc_span::symbol::{sym, Ident};
use rustc_span::Span;
@ -923,17 +924,16 @@ impl<'a, 'tcx> Visitor<'tcx> for BoundVarContext<'a, 'tcx> {
origin,
..
}) => {
let (bound_vars, binders): (FxIndexMap<LocalDefId, ResolvedArg>, Vec<_>) =
bound_generic_params
.iter()
.enumerate()
.map(|(late_bound_idx, param)| {
let pair = ResolvedArg::late(late_bound_idx as u32, param);
let r = late_arg_as_bound_arg(this.tcx, &pair.1, param);
(pair, r)
})
.unzip();
.iter()
.enumerate()
.map(|(late_bound_idx, param)| {
let pair = ResolvedArg::late(late_bound_idx as u32, param);
let r = late_arg_as_bound_arg(this.tcx, &pair.1, param);
(pair, r)
})
.unzip();
this.record_late_bound_vars(hir_id, binders.clone());
// Even if there are no lifetimes defined here, we still wrap it in a binder
// scope. If there happens to be a nested poly trait ref (an error), that
@ -968,20 +968,22 @@ impl<'a, 'tcx> Visitor<'tcx> for BoundVarContext<'a, 'tcx> {
continue;
}
this.insert_lifetime(lt, ResolvedArg::StaticLifetime);
this.tcx
.sess
.struct_span_warn(
lifetime.ident.span,
&format!(
"unnecessary lifetime parameter `{}`",
this.tcx.struct_span_lint_hir(
lint::builtin::UNUSED_LIFETIMES,
lifetime.hir_id,
lifetime.ident.span,
format!(
"unnecessary lifetime parameter `{}`",
lifetime.ident
),
|lint| {
let help = &format!(
"you can use the `'static` lifetime directly, in place of `{}`",
lifetime.ident,
),
)
.help(&format!(
"you can use the `'static` lifetime directly, in place of `{}`",
lifetime.ident,
))
.emit();
);
lint.help(help)
},
);
}
}
}

0
tests/ui/generic-associated-types/method-unsatified-assoc-type-predicate.rs → tests/ui/generic-associated-types/method-unsatisfied-assoc-type-predicate.rs
View File

4
tests/ui/generic-associated-types/method-unsatified-assoc-type-predicate.stderr → tests/ui/generic-associated-types/method-unsatisfied-assoc-type-predicate.stderr
View File

@ -1,5 +1,5 @@
error[E0599]: the method `f` exists for struct `S`, but its trait bounds were not satisfied
--> $DIR/method-unsatified-assoc-type-predicate.rs:28:7
--> $DIR/method-unsatisfied-assoc-type-predicate.rs:28:7
|
LL | struct S;
| --------
@ -12,7 +12,7 @@ LL | a.f();
| ^ method cannot be called on `S` due to unsatisfied trait bounds
|
note: trait bound `<S as X>::Y<i32> = i32` was not satisfied
--> $DIR/method-unsatified-assoc-type-predicate.rs:12:11
--> $DIR/method-unsatisfied-assoc-type-predicate.rs:12:11
|
LL | impl<T: X<Y<i32> = i32>> M for T {}
| ^^^^^^^^^^^^ - -

2
tests/ui/generic-associated-types/unsatified-item-lifetime-bound.rs → tests/ui/generic-associated-types/unsatisfied-item-lifetime-bound.rs
View File

@ -1,3 +1,5 @@
#![warn(unused_lifetimes)]
pub trait X {
type Y<'a: 'static>;
//~^ WARNING unnecessary lifetime parameter

19
tests/ui/generic-associated-types/unsatified-item-lifetime-bound.stderr → tests/ui/generic-associated-types/unsatisfied-item-lifetime-bound.stderr
View File

@ -1,45 +1,50 @@
warning: unnecessary lifetime parameter `'a`
--> $DIR/unsatified-item-lifetime-bound.rs:2:12
--> $DIR/unsatisfied-item-lifetime-bound.rs:4:12
|
LL | type Y<'a: 'static>;
| ^^
|
= help: you can use the `'static` lifetime directly, in place of `'a`
note: the lint level is defined here
--> $DIR/unsatisfied-item-lifetime-bound.rs:1:9
|
LL | #![warn(unused_lifetimes)]
| ^^^^^^^^^^^^^^^^
error[E0478]: lifetime bound not satisfied
--> $DIR/unsatified-item-lifetime-bound.rs:11:8
--> $DIR/unsatisfied-item-lifetime-bound.rs:13:8
|
LL | f: <T as X>::Y<'a>,
| ^^^^^^^^^^^^^^^
|
note: lifetime parameter instantiated with the lifetime `'a` as defined here
--> $DIR/unsatified-item-lifetime-bound.rs:10:10
--> $DIR/unsatisfied-item-lifetime-bound.rs:12:10
|
LL | struct B<'a, T: for<'r> X<Y<'r> = &'r ()>> {
| ^^
= note: but lifetime parameter must outlive the static lifetime
error[E0478]: lifetime bound not satisfied
--> $DIR/unsatified-item-lifetime-bound.rs:16:8
--> $DIR/unsatisfied-item-lifetime-bound.rs:18:8
|
LL | f: <T as X>::Y<'a>,
| ^^^^^^^^^^^^^^^
|
note: lifetime parameter instantiated with the lifetime `'a` as defined here
--> $DIR/unsatified-item-lifetime-bound.rs:15:10
--> $DIR/unsatisfied-item-lifetime-bound.rs:17:10
|
LL | struct C<'a, T: X> {
| ^^
= note: but lifetime parameter must outlive the static lifetime
error[E0478]: lifetime bound not satisfied
--> $DIR/unsatified-item-lifetime-bound.rs:21:8
--> $DIR/unsatisfied-item-lifetime-bound.rs:23:8
|
LL | f: <() as X>::Y<'a>,
| ^^^^^^^^^^^^^^^^
|
note: lifetime parameter instantiated with the lifetime `'a` as defined here
--> $DIR/unsatified-item-lifetime-bound.rs:20:10
--> $DIR/unsatisfied-item-lifetime-bound.rs:22:10
|
LL | struct D<'a> {
| ^^

1
tests/ui/impl-trait/equal-hidden-lifetimes.rs
View File

@ -5,7 +5,6 @@
// `'a == 'static` so `&'a i32` is fine as the return type
fn equal_regions_static<'a: 'static>(x: &'a i32) -> impl Sized {
//~^ WARNING unnecessary lifetime parameter `'a`
x
}

10
tests/ui/impl-trait/equal-hidden-lifetimes.stderr
View File

@ -1,10 +0,0 @@
warning: unnecessary lifetime parameter `'a`
--> $DIR/equal-hidden-lifetimes.rs:7:25
|
LL | fn equal_regions_static<'a: 'static>(x: &'a i32) -> impl Sized {
| ^^
|
= help: you can use the `'static` lifetime directly, in place of `'a`
warning: 1 warning emitted

1
tests/ui/issues/issue-30438-c.rs
View File

@ -5,7 +5,6 @@ trait Trait { type Out; }
struct Test<'a> { s: &'a str }
fn silly<'y, 'z>(_s: &'y Test<'z>) -> &'y <Test<'z> as Trait>::Out where 'z: 'static {
//~^ WARN unnecessary lifetime parameter `'z`
let x = Test { s: "this cannot last" };
&x
//~^ ERROR: cannot return reference to local variable `x`

12
tests/ui/issues/issue-30438-c.stderr
View File

@ -1,17 +1,9 @@
warning: unnecessary lifetime parameter `'z`
--> $DIR/issue-30438-c.rs:7:74
|
LL | fn silly<'y, 'z>(_s: &'y Test<'z>) -> &'y <Test<'z> as Trait>::Out where 'z: 'static {
| ^^
|
= help: you can use the `'static` lifetime directly, in place of `'z`
error[E0515]: cannot return reference to local variable `x`
--> $DIR/issue-30438-c.rs:10:5
--> $DIR/issue-30438-c.rs:9:5
|
LL | &x
| ^^ returns a reference to data owned by the current function
error: aborting due to previous error; 1 warning emitted
error: aborting due to previous error
For more information about this error, try `rustc --explain E0515`.

2
tests/ui/regions/regions-free-region-outlives-static-outlives-free-region.rs
View File

@ -8,6 +8,8 @@
//
// 'a : 'b
#![warn(unused_lifetimes)]
fn test<'a,'b>(x: &'a i32) -> &'b i32
where 'a: 'static //~ WARN unnecessary lifetime parameter `'a`
{

7
tests/ui/regions/regions-free-region-outlives-static-outlives-free-region.stderr
View File

@ -1,10 +1,15 @@
warning: unnecessary lifetime parameter `'a`
--> $DIR/regions-free-region-outlives-static-outlives-free-region.rs:12:11
--> $DIR/regions-free-region-outlives-static-outlives-free-region.rs:14:11
|
LL | where 'a: 'static
| ^^
|
= help: you can use the `'static` lifetime directly, in place of `'a`
note: the lint level is defined here
--> $DIR/regions-free-region-outlives-static-outlives-free-region.rs:11:9
|
LL | #![warn(unused_lifetimes)]
| ^^^^^^^^^^^^^^^^
warning: 1 warning emitted

2
tests/ui/regions/regions-static-bound-rpass.rs
View File

@ -1,5 +1,7 @@
// run-pass
#![warn(unused_lifetimes)]
fn invariant_id<'a,'b>(t: &'b mut &'static ()) -> &'b mut &'a ()
where 'a: 'static { t }
//~^ WARN unnecessary lifetime parameter `'a`

11
tests/ui/regions/regions-static-bound-rpass.stderr
View File

@ -1,13 +1,18 @@
warning: unnecessary lifetime parameter `'a`
--> $DIR/regions-static-bound-rpass.rs:4:11
--> $DIR/regions-static-bound-rpass.rs:6:11
|
LL | where 'a: 'static { t }
| ^^
|
= help: you can use the `'static` lifetime directly, in place of `'a`
note: the lint level is defined here
--> $DIR/regions-static-bound-rpass.rs:3:9
|
LL | #![warn(unused_lifetimes)]
| ^^^^^^^^^^^^^^^^
warning: unnecessary lifetime parameter `'a`
--> $DIR/regions-static-bound-rpass.rs:8:11
--> $DIR/regions-static-bound-rpass.rs:10:11
|
LL | where 'a: 'static { t }
| ^^
@ -15,7 +20,7 @@ LL | where 'a: 'static { t }
= help: you can use the `'static` lifetime directly, in place of `'a`
warning: unnecessary lifetime parameter `'b`
--> $DIR/regions-static-bound-rpass.rs:12:19
--> $DIR/regions-static-bound-rpass.rs:14:19
|
LL | where 'a: 'b, 'b: 'static { t }
| ^^

8
tests/ui/regions/regions-static-bound.rs
View File

@ -1,6 +1,8 @@
fn static_id<'a,'b>(t: &'a ()) -> &'static ()
where 'a: 'static { t }
//~^ WARN unnecessary lifetime parameter `'a`
#![warn(unused_lifetimes)]
fn static_id<'a,'b>(t: &'a ()) -> &'static () where 'a: 'static { t }
//~^ WARN lifetime parameter `'b` never used
//~| WARN unnecessary lifetime parameter `'a`
fn static_id_indirect<'a,'b>(t: &'a ()) -> &'static ()
where 'a: 'b, 'b: 'static { t }

32
tests/ui/regions/regions-static-bound.stderr
View File

@ -1,13 +1,27 @@
warning: unnecessary lifetime parameter `'a`
--> $DIR/regions-static-bound.rs:2:11
warning: lifetime parameter `'b` never used
--> $DIR/regions-static-bound.rs:3:17
|
LL | where 'a: 'static { t }
| ^^
LL | fn static_id<'a,'b>(t: &'a ()) -> &'static () where 'a: 'static { t }
| -^^
| |
| help: elide the unused lifetime
|
note: the lint level is defined here
--> $DIR/regions-static-bound.rs:1:9
|
LL | #![warn(unused_lifetimes)]
| ^^^^^^^^^^^^^^^^
warning: unnecessary lifetime parameter `'a`
--> $DIR/regions-static-bound.rs:3:53
|
LL | fn static_id<'a,'b>(t: &'a ()) -> &'static () where 'a: 'static { t }
| ^^
|
= help: you can use the `'static` lifetime directly, in place of `'a`
warning: unnecessary lifetime parameter `'b`
--> $DIR/regions-static-bound.rs:6:19
--> $DIR/regions-static-bound.rs:8:19
|
LL | where 'a: 'b, 'b: 'static { t }
| ^^
@ -15,7 +29,7 @@ LL | where 'a: 'b, 'b: 'static { t }
= help: you can use the `'static` lifetime directly, in place of `'b`
error: lifetime may not live long enough
--> $DIR/regions-static-bound.rs:10:5
--> $DIR/regions-static-bound.rs:12:5
|
LL | fn static_id_wrong_way<'a>(t: &'a ()) -> &'static () where 'static: 'a {
| -- lifetime `'a` defined here
@ -23,7 +37,7 @@ LL | t
| ^ returning this value requires that `'a` must outlive `'static`
error[E0521]: borrowed data escapes outside of function
--> $DIR/regions-static-bound.rs:15:5
--> $DIR/regions-static-bound.rs:17:5
|
LL | fn error(u: &(), v: &()) {
| - - let's call the lifetime of this reference `'1`
@ -36,7 +50,7 @@ LL | static_id(&u);
| argument requires that `'1` must outlive `'static`
error[E0521]: borrowed data escapes outside of function
--> $DIR/regions-static-bound.rs:17:5
--> $DIR/regions-static-bound.rs:19:5
|
LL | fn error(u: &(), v: &()) {
| - - let's call the lifetime of this reference `'2`
@ -49,6 +63,6 @@ LL | static_id_indirect(&v);
| `v` escapes the function body here
| argument requires that `'2` must outlive `'static`
error: aborting due to 3 previous errors; 2 warnings emitted
error: aborting due to 3 previous errors; 3 warnings emitted
For more information about this error, try `rustc --explain E0521`.

2
tests/ui/static/static-lifetime-bound.rs
View File

@ -1,4 +1,4 @@
fn f<'a: 'static>(_: &'a i32) {} //~WARN unnecessary lifetime parameter `'a`
fn f<'a: 'static>(_: &'a i32) {}
fn main() {
let x = 0;

10
tests/ui/static/static-lifetime-bound.stderr
View File

@ -1,11 +1,3 @@
warning: unnecessary lifetime parameter `'a`
--> $DIR/static-lifetime-bound.rs:1:6
|
LL | fn f<'a: 'static>(_: &'a i32) {}
| ^^
|
= help: you can use the `'static` lifetime directly, in place of `'a`
error[E0597]: `x` does not live long enough
--> $DIR/static-lifetime-bound.rs:5:7
|
@ -19,6 +11,6 @@ LL | f(&x);
LL | }
| - `x` dropped here while still borrowed
error: aborting due to previous error; 1 warning emitted
error: aborting due to previous error
For more information about this error, try `rustc --explain E0597`.

1
tests/ui/type-alias-impl-trait/bounds-are-checked.rs
View File

@ -6,7 +6,6 @@
type X<'a> = impl Into<&'static str> + From<&'a str>;
fn f<'a: 'static>(t: &'a str) -> X<'a> {
//~^ WARNING unnecessary lifetime parameter
t
//~^ ERROR expected generic lifetime parameter, found `'static`
}

12
tests/ui/type-alias-impl-trait/bounds-are-checked.stderr
View File

@ -1,13 +1,5 @@
warning: unnecessary lifetime parameter `'a`
--> $DIR/bounds-are-checked.rs:8:6
|
LL | fn f<'a: 'static>(t: &'a str) -> X<'a> {
| ^^
|
= help: you can use the `'static` lifetime directly, in place of `'a`
error[E0792]: expected generic lifetime parameter, found `'static`
--> $DIR/bounds-are-checked.rs:10:5
--> $DIR/bounds-are-checked.rs:9:5
|
LL | type X<'a> = impl Into<&'static str> + From<&'a str>;
| -- cannot use static lifetime; use a bound lifetime instead or remove the lifetime parameter from the opaque type
@ -15,6 +7,6 @@ LL | type X<'a> = impl Into<&'static str> + From<&'a str>;
LL | t
| ^
error: aborting due to previous error; 1 warning emitted
error: aborting due to previous error
For more information about this error, try `rustc --explain E0792`.

3
tests/ui/type-alias-impl-trait/implied_lifetime_wf_check3.rs
View File

@ -4,7 +4,6 @@ mod test_lifetime_param {
type Ty<'a> = impl Sized + 'a;
fn defining(a: &str) -> Ty<'_> { a }
fn assert_static<'a: 'static>() {}
//~^ WARN: unnecessary lifetime parameter `'a`
fn test<'a>() where Ty<'a>: 'static { assert_static::<'a>() }
//~^ ERROR: lifetime may not live long enough
}
@ -13,14 +12,12 @@ mod test_higher_kinded_lifetime_param {
type Ty<'a> = impl Sized + 'a;
fn defining(a: &str) -> Ty<'_> { a }
fn assert_static<'a: 'static>() {}
//~^ WARN: unnecessary lifetime parameter `'a`
fn test<'a>() where for<'b> Ty<'b>: 'a { assert_static::<'a>() }
//~^ ERROR: lifetime may not live long enough
}
mod test_higher_kinded_lifetime_param2 {
fn assert_static<'a: 'static>() {}
//~^ WARN: unnecessary lifetime parameter `'a`
fn test<'a>() { assert_static::<'a>() }
//~^ ERROR: lifetime may not live long enough
}

34
tests/ui/type-alias-impl-trait/implied_lifetime_wf_check3.stderr
View File

@ -1,41 +1,17 @@
warning: unnecessary lifetime parameter `'a`
--> $DIR/implied_lifetime_wf_check3.rs:6:22
|
LL | fn assert_static<'a: 'static>() {}
| ^^
|
= help: you can use the `'static` lifetime directly, in place of `'a`
warning: unnecessary lifetime parameter `'a`
--> $DIR/implied_lifetime_wf_check3.rs:15:22
|
LL | fn assert_static<'a: 'static>() {}
| ^^
|
= help: you can use the `'static` lifetime directly, in place of `'a`
warning: unnecessary lifetime parameter `'a`
--> $DIR/implied_lifetime_wf_check3.rs:22:22
|
LL | fn assert_static<'a: 'static>() {}
| ^^
|
= help: you can use the `'static` lifetime directly, in place of `'a`
error: lifetime may not live long enough
--> $DIR/implied_lifetime_wf_check3.rs:8:43
--> $DIR/implied_lifetime_wf_check3.rs:7:43
|
LL | fn test<'a>() where Ty<'a>: 'static { assert_static::<'a>() }
| -- lifetime `'a` defined here ^^^^^^^^^^^^^^^^^^^ requires that `'a` must outlive `'static`
error: lifetime may not live long enough
--> $DIR/implied_lifetime_wf_check3.rs:17:46
--> $DIR/implied_lifetime_wf_check3.rs:15:46
|
LL | fn test<'a>() where for<'b> Ty<'b>: 'a { assert_static::<'a>() }
| -- lifetime `'a` defined here ^^^^^^^^^^^^^^^^^^^ requires that `'a` must outlive `'static`
error: lifetime may not live long enough
--> $DIR/implied_lifetime_wf_check3.rs:24:21
--> $DIR/implied_lifetime_wf_check3.rs:21:21
|
LL | fn test<'a>() { assert_static::<'a>() }
| -- ^^^^^^^^^^^^^^^^^^^ requires that `'a` must outlive `'static`
@ -43,7 +19,7 @@ LL | fn test<'a>() { assert_static::<'a>() }
| lifetime `'a` defined here
error[E0310]: the parameter type `A` may not live long enough
--> $DIR/implied_lifetime_wf_check3.rs:32:41
--> $DIR/implied_lifetime_wf_check3.rs:29:41
|
LL | fn test<A>() where Ty<A>: 'static { assert_static::<A>() }
| ^^^^^^^^^^^^^^^^^^ ...so that the type `A` will meet its required lifetime bounds
@ -53,6 +29,6 @@ help: consider adding an explicit lifetime bound...
LL | fn test<A: 'static>() where Ty<A>: 'static { assert_static::<A>() }
| +++++++++
error: aborting due to 4 previous errors; 3 warnings emitted
error: aborting due to 4 previous errors
For more information about this error, try `rustc --explain E0310`.