From 23cf5dd9cf32f4df511b96eaec1c8565128fa804 Mon Sep 17 00:00:00 2001
From: Jeremy Davis <jeremydavis519@gmail.com>
Date: Mon, 13 Jun 2022 19:43:34 -0500
Subject: [PATCH 1/4] Define the `named_static_lifetimes` lint
This lint will replace the existing hard-warning.
---
compiler/rustc_lint_defs/src/builtin.rs | 35 +++++++++++++++++++++++++
1 file changed, 35 insertions(+)
diff --git a/compiler/rustc_lint_defs/src/builtin.rs b/compiler/rustc_lint_defs/src/builtin.rs
index a067534b18938..2baaad0c642f6 100644
--- a/compiler/rustc_lint_defs/src/builtin.rs
+++ b/compiler/rustc_lint_defs/src/builtin.rs
@@ -1621,6 +1621,40 @@ declare_lint! {
"detects lifetime parameters that are never used"
}
+declare_lint! {
+ /// The `named_static_lifetimes` lint detects lifetime parameters that are
+ /// defined as outliving the static lifetime.
+ ///
+ /// ### Example
+ ///
+ /// ```rust,compile_fail
+ /// #[deny(named_static_lifetimes)]
+ ///
+ /// pub fn foo<'a>(_s: &'a str) where 'a: 'static {}
+ /// ```
+ ///
+ /// {{produces}}
+ ///
+ /// ### Explanation
+ ///
+ /// By definition, the static lifetime (`'static`) outlives every other
+ /// lifetime. If another lifetime `'a` lives at least as long as `'static`,
+ /// then it is identical to `'static`. In that case, there is no need for
+ /// the name `'a`, and it likely only makes the code harder to read.
+ ///
+ /// To fix this, consider using `'static` instead of the named lifetime.
+ /// Here is the result of doing that in the example above:
+ ///
+ /// ```rust
+ /// #[deny(named_static_lifetimes)]
+ ///
+ /// pub fn foo(_s: &'static str) {}
+ /// ```
+ pub NAMED_STATIC_LIFETIMES,
+ Warn,
+ "detects lifetime parameters that are identical to `'static`"
+}
+
declare_lint! {
/// The `tyvar_behind_raw_pointer` lint detects raw pointer to an
/// inference variable.
@@ -3174,6 +3208,7 @@ declare_lint_pass! {
UNCONDITIONAL_RECURSION,
SINGLE_USE_LIFETIMES,
UNUSED_LIFETIMES,
+ NAMED_STATIC_LIFETIMES,
UNUSED_LABELS,
TYVAR_BEHIND_RAW_POINTER,
ELIDED_LIFETIMES_IN_PATHS,
From cc9f4c2debc85f14f27d8514aa8ed2ec7d9467dd Mon Sep 17 00:00:00 2001
From: Jeremy Davis <jeremydavis519@gmail.com>
Date: Mon, 13 Jun 2022 20:41:48 -0500
Subject: [PATCH 2/4] Replace the named static lifetime hard-warning with the
new lint
---
Cargo.lock | 1 +
compiler/rustc_resolve/Cargo.toml | 1 +
compiler/rustc_resolve/src/late/lifetimes.rs | 29 ++++++++++++--------
3 files changed, 19 insertions(+), 12 deletions(-)
diff --git a/Cargo.lock b/Cargo.lock
index 51b0da65b3145..33d0973ab5d54 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -4380,6 +4380,7 @@ dependencies = [
"rustc_feature",
"rustc_hir",
"rustc_index",
+ "rustc_lint_defs",
"rustc_metadata",
"rustc_middle",
"rustc_query_system",
diff --git a/compiler/rustc_resolve/Cargo.toml b/compiler/rustc_resolve/Cargo.toml
index b2178ff59954b..33436c6ee83d2 100644
--- a/compiler/rustc_resolve/Cargo.toml
+++ b/compiler/rustc_resolve/Cargo.toml
@@ -21,6 +21,7 @@ rustc_expand = { path = "../rustc_expand" }
rustc_feature = { path = "../rustc_feature" }
rustc_hir = { path = "../rustc_hir" }
rustc_index = { path = "../rustc_index" }
+rustc_lint_defs = { path = "../rustc_lint_defs" }
rustc_metadata = { path = "../rustc_metadata" }
rustc_query_system = { path = "../rustc_query_system" }
rustc_session = { path = "../rustc_session" }
diff --git a/compiler/rustc_resolve/src/late/lifetimes.rs b/compiler/rustc_resolve/src/late/lifetimes.rs
index 447f4174c10d5..e5c565e4f96c9 100644
--- a/compiler/rustc_resolve/src/late/lifetimes.rs
+++ b/compiler/rustc_resolve/src/late/lifetimes.rs
@@ -16,6 +16,7 @@ use rustc_hir::def_id::{DefIdMap, LocalDefId};
use rustc_hir::intravisit::{self, Visitor};
use rustc_hir::{GenericArg, GenericParam, LifetimeName, Node};
use rustc_hir::{GenericParamKind, HirIdMap};
+use rustc_lint_defs::builtin::NAMED_STATIC_LIFETIMES;
use rustc_middle::hir::map::Map;
use rustc_middle::hir::nested_filter;
use rustc_middle::middle::resolve_lifetime::*;
@@ -1255,20 +1256,24 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
continue;
}
this.insert_lifetime(lt, Region::Static);
- this.tcx
- .sess
- .struct_span_warn(
- lifetime.span,
- &format!(
+ this.tcx.struct_span_lint_hir(
+ NAMED_STATIC_LIFETIMES,
+ lifetime.hir_id,
+ lifetime.span,
+ |lint| {
+ let msg = &format!(
"unnecessary lifetime parameter `{}`",
lifetime.name.ident(),
- ),
- )
- .help(&format!(
- "you can use the `'static` lifetime directly, in place of `{}`",
- lifetime.name.ident(),
- ))
- .emit();
+ );
+ let help = &format!(
+ "you can use the `'static` lifetime directly, in place of `{}`",
+ lifetime.name.ident(),
+ );
+ lint.build(msg)
+ .help(help)
+ .emit();
+ },
+ );
}
}
}
From 47ed1a3d61a62124937e14720d4c46c8ca28a725 Mon Sep 17 00:00:00 2001
From: Jeremy Davis <jeremydavis519@gmail.com>
Date: Mon, 13 Jun 2022 23:36:01 -0500
Subject: [PATCH 3/4] Update the UI tests for the `named_static_lifetimes` lint
---
.../unsatified-item-lifetime-bound.stderr | 1 +
src/test/ui/impl-trait/equal-hidden-lifetimes.stderr | 1 +
src/test/ui/issues/issue-30438-c.stderr | 1 +
...gions-free-region-outlives-static-outlives-free-region.stderr | 1 +
src/test/ui/regions/regions-static-bound-rpass.stderr | 1 +
src/test/ui/regions/regions-static-bound.stderr | 1 +
src/test/ui/static/static-lifetime-bound.stderr | 1 +
src/test/ui/type-alias-impl-trait/bounds-are-checked.stderr | 1 +
8 files changed, 8 insertions(+)
diff --git a/src/test/ui/generic-associated-types/unsatified-item-lifetime-bound.stderr b/src/test/ui/generic-associated-types/unsatified-item-lifetime-bound.stderr
index ae52010cc50a2..1b600913d6445 100644
--- a/src/test/ui/generic-associated-types/unsatified-item-lifetime-bound.stderr
+++ b/src/test/ui/generic-associated-types/unsatified-item-lifetime-bound.stderr
@@ -4,6 +4,7 @@ warning: unnecessary lifetime parameter `'a`
LL | type Y<'a: 'static>;
| ^^
|
+ = note: `#[warn(named_static_lifetimes)]` on by default
= help: you can use the `'static` lifetime directly, in place of `'a`
error[E0478]: lifetime bound not satisfied
diff --git a/src/test/ui/impl-trait/equal-hidden-lifetimes.stderr b/src/test/ui/impl-trait/equal-hidden-lifetimes.stderr
index 3e48aef553b16..2a3c9f270888f 100644
--- a/src/test/ui/impl-trait/equal-hidden-lifetimes.stderr
+++ b/src/test/ui/impl-trait/equal-hidden-lifetimes.stderr
@@ -4,6 +4,7 @@ warning: unnecessary lifetime parameter `'a`
LL | fn equal_regions_static<'a: 'static>(x: &'a i32) -> impl Sized {
| ^^
|
+ = note: `#[warn(named_static_lifetimes)]` on by default
= help: you can use the `'static` lifetime directly, in place of `'a`
warning: 1 warning emitted
diff --git a/src/test/ui/issues/issue-30438-c.stderr b/src/test/ui/issues/issue-30438-c.stderr
index a7a5c0500fd23..d06d740ccc709 100644
--- a/src/test/ui/issues/issue-30438-c.stderr
+++ b/src/test/ui/issues/issue-30438-c.stderr
@@ -4,6 +4,7 @@ warning: unnecessary lifetime parameter `'z`
LL | fn silly<'y, 'z>(_s: &'y Test<'z>) -> &'y <Test<'z> as Trait>::Out where 'z: 'static {
| ^^
|
+ = note: `#[warn(named_static_lifetimes)]` on by default
= help: you can use the `'static` lifetime directly, in place of `'z`
error[E0515]: cannot return reference to local variable `x`
diff --git a/src/test/ui/regions/regions-free-region-outlives-static-outlives-free-region.stderr b/src/test/ui/regions/regions-free-region-outlives-static-outlives-free-region.stderr
index 70ed418d5cbbb..94d85913c56a9 100644
--- a/src/test/ui/regions/regions-free-region-outlives-static-outlives-free-region.stderr
+++ b/src/test/ui/regions/regions-free-region-outlives-static-outlives-free-region.stderr
@@ -4,6 +4,7 @@ warning: unnecessary lifetime parameter `'a`
LL | where 'a: 'static
| ^^
|
+ = note: `#[warn(named_static_lifetimes)]` on by default
= help: you can use the `'static` lifetime directly, in place of `'a`
warning: 1 warning emitted
diff --git a/src/test/ui/regions/regions-static-bound-rpass.stderr b/src/test/ui/regions/regions-static-bound-rpass.stderr
index 9355a409d5099..298c4ce8b8fbe 100644
--- a/src/test/ui/regions/regions-static-bound-rpass.stderr
+++ b/src/test/ui/regions/regions-static-bound-rpass.stderr
@@ -4,6 +4,7 @@ warning: unnecessary lifetime parameter `'a`
LL | where 'a: 'static { t }
| ^^
|
+ = note: `#[warn(named_static_lifetimes)]` on by default
= help: you can use the `'static` lifetime directly, in place of `'a`
warning: unnecessary lifetime parameter `'a`
diff --git a/src/test/ui/regions/regions-static-bound.stderr b/src/test/ui/regions/regions-static-bound.stderr
index 2886ec3ead51f..678f55e08fadc 100644
--- a/src/test/ui/regions/regions-static-bound.stderr
+++ b/src/test/ui/regions/regions-static-bound.stderr
@@ -4,6 +4,7 @@ warning: unnecessary lifetime parameter `'a`
LL | where 'a: 'static { t }
| ^^
|
+ = note: `#[warn(named_static_lifetimes)]` on by default
= help: you can use the `'static` lifetime directly, in place of `'a`
warning: unnecessary lifetime parameter `'b`
diff --git a/src/test/ui/static/static-lifetime-bound.stderr b/src/test/ui/static/static-lifetime-bound.stderr
index ef07a89315f40..cc7d9b14b4f2f 100644
--- a/src/test/ui/static/static-lifetime-bound.stderr
+++ b/src/test/ui/static/static-lifetime-bound.stderr
@@ -4,6 +4,7 @@ warning: unnecessary lifetime parameter `'a`
LL | fn f<'a: 'static>(_: &'a i32) {}
| ^^
|
+ = note: `#[warn(named_static_lifetimes)]` on by default
= help: you can use the `'static` lifetime directly, in place of `'a`
error[E0597]: `x` does not live long enough
diff --git a/src/test/ui/type-alias-impl-trait/bounds-are-checked.stderr b/src/test/ui/type-alias-impl-trait/bounds-are-checked.stderr
index 920eef11da4b9..79ad389c03b75 100644
--- a/src/test/ui/type-alias-impl-trait/bounds-are-checked.stderr
+++ b/src/test/ui/type-alias-impl-trait/bounds-are-checked.stderr
@@ -4,6 +4,7 @@ warning: unnecessary lifetime parameter `'a`
LL | fn f<'a: 'static>(t: &'a str) -> X<'a> {
| ^^
|
+ = note: `#[warn(named_static_lifetimes)]` on by default
= help: you can use the `'static` lifetime directly, in place of `'a`
error: non-defining opaque type use in defining scope
From 897f4d5ccee64f177ff39b781546907697f265ef Mon Sep 17 00:00:00 2001
From: Jeremy Davis <jeremydavis519@gmail.com>
Date: Tue, 14 Jun 2022 09:45:06 -0500
Subject: [PATCH 4/4] Remove the direct dependency on `rustc_lint_defs`
---
Cargo.lock | 1 -
compiler/rustc_resolve/Cargo.toml | 1 -
compiler/rustc_resolve/src/late/lifetimes.rs | 4 ++--
3 files changed, 2 insertions(+), 4 deletions(-)
diff --git a/Cargo.lock b/Cargo.lock
index 33d0973ab5d54..51b0da65b3145 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -4380,7 +4380,6 @@ dependencies = [
"rustc_feature",
"rustc_hir",
"rustc_index",
- "rustc_lint_defs",
"rustc_metadata",
"rustc_middle",
"rustc_query_system",
diff --git a/compiler/rustc_resolve/Cargo.toml b/compiler/rustc_resolve/Cargo.toml
index 33436c6ee83d2..b2178ff59954b 100644
--- a/compiler/rustc_resolve/Cargo.toml
+++ b/compiler/rustc_resolve/Cargo.toml
@@ -21,7 +21,6 @@ rustc_expand = { path = "../rustc_expand" }
rustc_feature = { path = "../rustc_feature" }
rustc_hir = { path = "../rustc_hir" }
rustc_index = { path = "../rustc_index" }
-rustc_lint_defs = { path = "../rustc_lint_defs" }
rustc_metadata = { path = "../rustc_metadata" }
rustc_query_system = { path = "../rustc_query_system" }
rustc_session = { path = "../rustc_session" }
diff --git a/compiler/rustc_resolve/src/late/lifetimes.rs b/compiler/rustc_resolve/src/late/lifetimes.rs
index e5c565e4f96c9..87898ca4ee897 100644
--- a/compiler/rustc_resolve/src/late/lifetimes.rs
+++ b/compiler/rustc_resolve/src/late/lifetimes.rs
@@ -16,12 +16,12 @@ use rustc_hir::def_id::{DefIdMap, LocalDefId};
use rustc_hir::intravisit::{self, Visitor};
use rustc_hir::{GenericArg, GenericParam, LifetimeName, Node};
use rustc_hir::{GenericParamKind, HirIdMap};
-use rustc_lint_defs::builtin::NAMED_STATIC_LIFETIMES;
use rustc_middle::hir::map::Map;
use rustc_middle::hir::nested_filter;
use rustc_middle::middle::resolve_lifetime::*;
use rustc_middle::ty::{self, GenericParamDefKind, TyCtxt};
use rustc_middle::{bug, span_bug};
+use rustc_session::lint;
use rustc_span::def_id::DefId;
use rustc_span::symbol::{kw, sym, Ident};
use rustc_span::Span;
@@ -1257,7 +1257,7 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
}
this.insert_lifetime(lt, Region::Static);
this.tcx.struct_span_lint_hir(
- NAMED_STATIC_LIFETIMES,
+ lint::builtin::NAMED_STATIC_LIFETIMES,
lifetime.hir_id,
lifetime.span,
|lint| {