Actually, just reuse the UNUSED_LIFETIMES lint

13 files changed, 107 insertions, 124 deletions

diff --git a/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs b/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs
index 0b8ac9926e4..affd678fc6c 100644
--- a/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs
+++ b/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs
@@ -20,7 +20,6 @@ use rustc_middle::hir::nested_filter;
 use rustc_middle::middle::resolve_bound_vars::*;
 use rustc_middle::query::Providers;
 use rustc_middle::ty::{self, TyCtxt, TypeSuperVisitable, TypeVisitor};
-use rustc_session::lint;
 use rustc_span::def_id::DefId;
 use rustc_span::symbol::{sym, Ident};
 use rustc_span::Span;
@@ -867,31 +866,6 @@ impl<'a, 'tcx> Visitor<'tcx> for BoundVarContext<'a, 'tcx> {
             }) => {
                 self.visit_lifetime(lifetime);
                 walk_list!(self, visit_param_bound, bounds);
-
-                if lifetime.res != hir::LifetimeName::Static {
-                    for bound in bounds {
-                        let hir::GenericBound::Outlives(lt) = bound else {
-                            continue;
-                        };
-                        if lt.res != hir::LifetimeName::Static {
-                            continue;
-                        }
-                        self.insert_lifetime(lt, ResolvedArg::StaticLifetime);
-                        self.tcx.node_span_lint(
-                            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,
-                                );
-                                lint.help(help);
-                            },
-                        );
-                    }
-                }
             }
             &hir::WherePredicate::EqPredicate(hir::WhereEqPredicate { lhs_ty, rhs_ty, .. }) => {
                 self.visit_ty(lhs_ty);
diff --git a/compiler/rustc_lint/messages.ftl b/compiler/rustc_lint/messages.ftl
index ad0a5a2b624..cc7a87544bc 100644
--- a/compiler/rustc_lint/messages.ftl
+++ b/compiler/rustc_lint/messages.ftl
@@ -534,7 +534,8 @@ lint_reason_must_be_string_literal = reason must be a string literal
 
 lint_reason_must_come_last = reason in lint attribute must come last
 
-lint_redundant_lifetime_args = lifetime `{$victim}` is required to be equal to `{$candidate}`, and is redundant and can be removed
+lint_redundant_lifetime_args = unnecessary lifetime parameter `{$victim}`
+    .note = you can use the `{$candidate}` lifetime directly, in place of `{$victim}`
 
 lint_redundant_semicolons =
     unnecessary trailing {$multiple ->
diff --git a/compiler/rustc_lint/src/redundant_lifetime_args.rs b/compiler/rustc_lint/src/redundant_lifetime_args.rs
index 7a7c5387369..59d2edba124 100644
--- a/compiler/rustc_lint/src/redundant_lifetime_args.rs
+++ b/compiler/rustc_lint/src/redundant_lifetime_args.rs
@@ -8,19 +8,13 @@ use rustc_infer::infer::outlives::env::OutlivesEnvironment;
 use rustc_infer::infer::{SubregionOrigin, TyCtxtInferExt};
 use rustc_macros::LintDiagnostic;
 use rustc_middle::ty::{self, TyCtxt};
+use rustc_session::lint::builtin::UNUSED_LIFETIMES;
 use rustc_span::DUMMY_SP;
 use rustc_trait_selection::traits::{outlives_bounds::InferCtxtExt, ObligationCtxt};
 
 use crate::{LateContext, LateLintPass};
 
-declare_lint! {
-    /// Docs
-    pub REDUNDANT_LIFETIME_ARGS,
-    Allow,
-    "do something"
-}
-
-declare_lint_pass!(RedundantLifetimeArgs => [REDUNDANT_LIFETIME_ARGS]);
+declare_lint_pass!(RedundantLifetimeArgs => []);
 
 impl<'tcx> LateLintPass<'tcx> for RedundantLifetimeArgs {
     fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'tcx>) {
@@ -142,10 +136,10 @@ fn check<'tcx>(tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>, owner_id: hir::
             if infcx.resolve_regions(outlives_env).is_empty() {
                 shadowed.insert(victim);
                 tcx.emit_spanned_lint(
-                    REDUNDANT_LIFETIME_ARGS,
+                    UNUSED_LIFETIMES,
                     tcx.local_def_id_to_hir_id(def_id.expect_local()),
                     tcx.def_span(def_id),
-                    RedundantLifetimeArgsList { candidate, victim },
+                    RedundantLifetimeArgsLint { candidate, victim },
                 );
             }
         }
@@ -154,7 +148,8 @@ fn check<'tcx>(tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>, owner_id: hir::
 
 #[derive(LintDiagnostic)]
 #[diag(lint_redundant_lifetime_args)]
-struct RedundantLifetimeArgsList<'tcx> {
+#[note]
+struct RedundantLifetimeArgsLint<'tcx> {
     candidate: ty::Region<'tcx>,
     victim: ty::Region<'tcx>,
 }
diff --git a/tests/ui/generic-associated-types/unsatisfied-item-lifetime-bound.rs b/tests/ui/generic-associated-types/unsatisfied-item-lifetime-bound.rs
index a3f3b1a6d4d..1d427e89c21 100644
--- a/tests/ui/generic-associated-types/unsatisfied-item-lifetime-bound.rs
+++ b/tests/ui/generic-associated-types/unsatisfied-item-lifetime-bound.rs
@@ -1,8 +1,5 @@
-#![warn(unused_lifetimes)]
-
 pub trait X {
     type Y<'a: 'static>;
-    //~^ WARNING unnecessary lifetime parameter
 }
 
 impl X for () {
diff --git a/tests/ui/generic-associated-types/unsatisfied-item-lifetime-bound.stderr b/tests/ui/generic-associated-types/unsatisfied-item-lifetime-bound.stderr
index 8d21b9172c8..cd2422b4f2d 100644
--- a/tests/ui/generic-associated-types/unsatisfied-item-lifetime-bound.stderr
+++ b/tests/ui/generic-associated-types/unsatisfied-item-lifetime-bound.stderr
@@ -1,18 +1,5 @@
-warning: unnecessary lifetime parameter `'a`
-  --> $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/unsatisfied-item-lifetime-bound.rs:9:18
+  --> $DIR/unsatisfied-item-lifetime-bound.rs:6:18
    |
 LL |     type Y<'a: 'static>;
    |     ------------------- definition of `Y` from trait
@@ -21,7 +8,7 @@ LL |     type Y<'a> = &'a ();
    |                  ^^^^^^
    |
 note: lifetime parameter instantiated with the lifetime `'a` as defined here
-  --> $DIR/unsatisfied-item-lifetime-bound.rs:9:12
+  --> $DIR/unsatisfied-item-lifetime-bound.rs:6:12
    |
 LL |     type Y<'a> = &'a ();
    |            ^^
@@ -32,44 +19,44 @@ LL |     type Y<'a> = &'a () where 'a: 'static;
    |                         +++++++++++++++++
 
 error[E0478]: lifetime bound not satisfied
-  --> $DIR/unsatisfied-item-lifetime-bound.rs:14:8
+  --> $DIR/unsatisfied-item-lifetime-bound.rs:11:8
    |
 LL |     f: <T as X>::Y<'a>,
    |        ^^^^^^^^^^^^^^^
    |
 note: lifetime parameter instantiated with the lifetime `'a` as defined here
-  --> $DIR/unsatisfied-item-lifetime-bound.rs:13:10
+  --> $DIR/unsatisfied-item-lifetime-bound.rs:10:10
    |
 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/unsatisfied-item-lifetime-bound.rs:19:8
+  --> $DIR/unsatisfied-item-lifetime-bound.rs:16:8
    |
 LL |     f: <T as X>::Y<'a>,
    |        ^^^^^^^^^^^^^^^
    |
 note: lifetime parameter instantiated with the lifetime `'a` as defined here
-  --> $DIR/unsatisfied-item-lifetime-bound.rs:18:10
+  --> $DIR/unsatisfied-item-lifetime-bound.rs:15:10
    |
 LL | struct C<'a, T: X> {
    |          ^^
    = note: but lifetime parameter must outlive the static lifetime
 
 error[E0478]: lifetime bound not satisfied
-  --> $DIR/unsatisfied-item-lifetime-bound.rs:24:8
+  --> $DIR/unsatisfied-item-lifetime-bound.rs:21:8
    |
 LL |     f: <() as X>::Y<'a>,
    |        ^^^^^^^^^^^^^^^^
    |
 note: lifetime parameter instantiated with the lifetime `'a` as defined here
-  --> $DIR/unsatisfied-item-lifetime-bound.rs:23:10
+  --> $DIR/unsatisfied-item-lifetime-bound.rs:20:10
    |
 LL | struct D<'a> {
    |          ^^
    = note: but lifetime parameter must outlive the static lifetime
 
-error: aborting due to 4 previous errors; 1 warning emitted
+error: aborting due to 4 previous errors
 
 For more information about this error, try `rustc --explain E0478`.
diff --git a/tests/ui/regions/regions-free-region-outlives-static-outlives-free-region.rs b/tests/ui/regions/regions-free-region-outlives-static-outlives-free-region.rs
index f6a628e97f5..5778466f92e 100644
--- a/tests/ui/regions/regions-free-region-outlives-static-outlives-free-region.rs
+++ b/tests/ui/regions/regions-free-region-outlives-static-outlives-free-region.rs
@@ -10,8 +10,8 @@
 
 #![warn(unused_lifetimes)]
 
-fn test<'a,'b>(x: &'a i32) -> &'b i32
-    where 'a: 'static //~ WARN unnecessary lifetime parameter `'a`
+fn test<'a,'b>(x: &'a i32) -> &'b i32 //~ WARN unnecessary lifetime parameter `'a`
+    where 'a: 'static
 {
     x
 }
diff --git a/tests/ui/regions/regions-free-region-outlives-static-outlives-free-region.stderr b/tests/ui/regions/regions-free-region-outlives-static-outlives-free-region.stderr
index 9f03a6553ba..69f409f436e 100644
--- a/tests/ui/regions/regions-free-region-outlives-static-outlives-free-region.stderr
+++ b/tests/ui/regions/regions-free-region-outlives-static-outlives-free-region.stderr
@@ -1,10 +1,10 @@
 warning: unnecessary lifetime parameter `'a`
-  --> $DIR/regions-free-region-outlives-static-outlives-free-region.rs:14:11
+  --> $DIR/regions-free-region-outlives-static-outlives-free-region.rs:13:9
    |
-LL |     where 'a: 'static
-   |           ^^
+LL | fn test<'a,'b>(x: &'a i32) -> &'b i32
+   |         ^^
    |
-   = help: you can use the `'static` lifetime directly, in place of `'a`
+   = note: 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
    |
diff --git a/tests/ui/regions/regions-static-bound-rpass.rs b/tests/ui/regions/regions-static-bound-rpass.rs
index 27da42882f3..028df1ac598 100644
--- a/tests/ui/regions/regions-static-bound-rpass.rs
+++ b/tests/ui/regions/regions-static-bound-rpass.rs
@@ -3,16 +3,17 @@
 #![warn(unused_lifetimes)]
 
 fn invariant_id<'a,'b>(t: &'b mut &'static ()) -> &'b mut &'a ()
-    where 'a: 'static { t }
 //~^ WARN unnecessary lifetime parameter `'a`
+    where 'a: 'static { t }
 
 fn static_id<'a>(t: &'a ()) -> &'static ()
-    where 'a: 'static { t }
 //~^ WARN unnecessary lifetime parameter `'a`
+    where 'a: 'static { t }
 
 fn static_id_indirect<'a,'b>(t: &'a ()) -> &'static ()
+//~^ WARN unnecessary lifetime parameter `'a`
+//~| WARN unnecessary lifetime parameter `'b`
     where 'a: 'b, 'b: 'static { t }
-//~^ WARN unnecessary lifetime parameter `'b`
 
 fn ref_id<'a>(t: &'a ()) -> &'a () where 'static: 'a { t }
 
diff --git a/tests/ui/regions/regions-static-bound-rpass.stderr b/tests/ui/regions/regions-static-bound-rpass.stderr
index f0f3a4c5261..d197266380a 100644
--- a/tests/ui/regions/regions-static-bound-rpass.stderr
+++ b/tests/ui/regions/regions-static-bound-rpass.stderr
@@ -1,10 +1,10 @@
 warning: unnecessary lifetime parameter `'a`
-  --> $DIR/regions-static-bound-rpass.rs:6:11
+  --> $DIR/regions-static-bound-rpass.rs:5:17
    |
-LL |     where 'a: 'static { t }
-   |           ^^
+LL | fn invariant_id<'a,'b>(t: &'b mut &'static ()) -> &'b mut &'a ()
+   |                 ^^
    |
-   = help: you can use the `'static` lifetime directly, in place of `'a`
+   = note: 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
    |
@@ -12,20 +12,28 @@ LL | #![warn(unused_lifetimes)]
    |         ^^^^^^^^^^^^^^^^
 
 warning: unnecessary lifetime parameter `'a`
-  --> $DIR/regions-static-bound-rpass.rs:10:11
+  --> $DIR/regions-static-bound-rpass.rs:9:14
    |
-LL |     where 'a: 'static { t }
-   |           ^^
+LL | fn static_id<'a>(t: &'a ()) -> &'static ()
+   |              ^^
    |
-   = help: you can use the `'static` lifetime directly, in place of `'a`
+   = note: you can use the `'static` lifetime directly, in place of `'a`
+
+warning: unnecessary lifetime parameter `'a`
+  --> $DIR/regions-static-bound-rpass.rs:13:23
+   |
+LL | fn static_id_indirect<'a,'b>(t: &'a ()) -> &'static ()
+   |                       ^^
+   |
+   = note: you can use the `'static` lifetime directly, in place of `'a`
 
 warning: unnecessary lifetime parameter `'b`
-  --> $DIR/regions-static-bound-rpass.rs:14:19
+  --> $DIR/regions-static-bound-rpass.rs:13:26
    |
-LL |     where 'a: 'b, 'b: 'static { t }
-   |                   ^^
+LL | fn static_id_indirect<'a,'b>(t: &'a ()) -> &'static ()
+   |                          ^^
    |
-   = help: you can use the `'static` lifetime directly, in place of `'b`
+   = note: you can use the `'static` lifetime directly, in place of `'b`
 
-warning: 3 warnings emitted
+warning: 4 warnings emitted
 
diff --git a/tests/ui/regions/regions-static-bound.rs b/tests/ui/regions/regions-static-bound.rs
index e7aa8795f01..af6425971bd 100644
--- a/tests/ui/regions/regions-static-bound.rs
+++ b/tests/ui/regions/regions-static-bound.rs
@@ -1,12 +1,7 @@
-#![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 }
-//~^ WARN unnecessary lifetime parameter `'b`
 
 fn static_id_wrong_way<'a>(t: &'a ()) -> &'static () where 'static: 'a {
     t
diff --git a/tests/ui/regions/regions-static-bound.stderr b/tests/ui/regions/regions-static-bound.stderr
index b314e9fe85d..f7b48349e4a 100644
--- a/tests/ui/regions/regions-static-bound.stderr
+++ b/tests/ui/regions/regions-static-bound.stderr
@@ -1,35 +1,5 @@
-warning: lifetime parameter `'b` never used
-  --> $DIR/regions-static-bound.rs:3:17
-   |
-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:8:19
-   |
-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:12:5
+  --> $DIR/regions-static-bound.rs:7:5
    |
 LL | fn static_id_wrong_way<'a>(t: &'a ()) -> &'static () where 'static: 'a {
    |                        -- lifetime `'a` defined here
@@ -37,7 +7,7 @@ LL |     t
    |     ^ returning this value requires that `'a` must outlive `'static`
 
 error[E0521]: borrowed data escapes outside of function
-  --> $DIR/regions-static-bound.rs:17:5
+  --> $DIR/regions-static-bound.rs:12:5
    |
 LL | fn error(u: &(), v: &()) {
    |          -  - let's call the lifetime of this reference `'1`
@@ -50,7 +20,7 @@ LL |     static_id(&u);
    |     argument requires that `'1` must outlive `'static`
 
 error[E0521]: borrowed data escapes outside of function
-  --> $DIR/regions-static-bound.rs:19:5
+  --> $DIR/regions-static-bound.rs:14:5
    |
 LL | fn error(u: &(), v: &()) {
    |                  -  - let's call the lifetime of this reference `'2`
@@ -63,6 +33,6 @@ 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; 3 warnings emitted
+error: aborting due to 3 previous errors
 
 For more information about this error, try `rustc --explain E0521`.
diff --git a/tests/ui/regions/transitively-redundant-lifetimes.rs b/tests/ui/regions/transitively-redundant-lifetimes.rs
new file mode 100644
index 00000000000..3baf2a88abb
--- /dev/null
+++ b/tests/ui/regions/transitively-redundant-lifetimes.rs
@@ -0,0 +1,16 @@
+#![allow(unused)]
+#![deny(unused_lifetimes)]
+
+fn a<'a, 'b>(x: &'a &'b &'a ()) {} //~ ERROR unnecessary lifetime parameter `'b`
+
+fn b<'a: 'b, 'b: 'a>() {} //~ ERROR unnecessary lifetime parameter `'b`
+
+struct Foo<T: 'static>(T);
+fn c<'a>(_: Foo<&'a ()>) {} //~ ERROR unnecessary lifetime parameter `'a`
+
+struct Bar<'a>(&'a ());
+impl<'a> Bar<'a> {
+    fn d<'b: 'a>(&'b self) {} //~ ERROR unnecessary lifetime parameter `'b`
+}
+
+fn main() {}
diff --git a/tests/ui/regions/transitively-redundant-lifetimes.stderr b/tests/ui/regions/transitively-redundant-lifetimes.stderr
new file mode 100644
index 00000000000..22a27115f7a
--- /dev/null
+++ b/tests/ui/regions/transitively-redundant-lifetimes.stderr
@@ -0,0 +1,39 @@
+error: unnecessary lifetime parameter `'b`
+  --> $DIR/transitively-redundant-lifetimes.rs:4:10
+   |
+LL | fn a<'a, 'b>(x: &'a &'b &'a ()) {}
+   |          ^^
+   |
+   = note: you can use the `'a` lifetime directly, in place of `'b`
+note: the lint level is defined here
+  --> $DIR/transitively-redundant-lifetimes.rs:2:9
+   |
+LL | #![deny(unused_lifetimes)]
+   |         ^^^^^^^^^^^^^^^^
+
+error: unnecessary lifetime parameter `'b`
+  --> $DIR/transitively-redundant-lifetimes.rs:6:14
+   |
+LL | fn b<'a: 'b, 'b: 'a>() {}
+   |              ^^
+   |
+   = note: you can use the `'a` lifetime directly, in place of `'b`
+
+error: unnecessary lifetime parameter `'a`
+  --> $DIR/transitively-redundant-lifetimes.rs:9:6
+   |
+LL | fn c<'a>(_: Foo<&'a ()>) {}
+   |      ^^
+   |
+   = note: you can use the `'static` lifetime directly, in place of `'a`
+
+error: unnecessary lifetime parameter `'b`
+  --> $DIR/transitively-redundant-lifetimes.rs:13:10
+   |
+LL |     fn d<'b: 'a>(&'b self) {}
+   |          ^^
+   |
+   = note: you can use the `'a` lifetime directly, in place of `'b`
+
+error: aborting due to 4 previous errors
+