From 9ef6e2199c885ffd671b321dfbf16ff0934f4d80 Mon Sep 17 00:00:00 2001
From: Alex Macleod <alex@macleod.io>
Date: Fri, 14 Jan 2022 14:24:25 +0000
Subject: [PATCH] `needless_lifetimes`: ignore lifetimes in explicit self types
---
clippy_lints/src/lifetimes.rs | 52 ++++++++++++++---
tests/ui/needless_lifetimes.rs | 51 +++++++++++++++-
tests/ui/needless_lifetimes.stderr | 94 +++++++++++++++++++++---------
3 files changed, 162 insertions(+), 35 deletions(-)
diff --git a/clippy_lints/src/lifetimes.rs b/clippy_lints/src/lifetimes.rs
index 0e2b78609c2c..618cf4b8b228 100644
--- a/clippy_lints/src/lifetimes.rs
+++ b/clippy_lints/src/lifetimes.rs
@@ -15,7 +15,7 @@ use rustc_lint::{LateContext, LateLintPass};
use rustc_middle::hir::map::Map;
use rustc_session::{declare_lint_pass, declare_tool_lint};
use rustc_span::source_map::Span;
-use rustc_span::symbol::{kw, Symbol};
+use rustc_span::symbol::{kw, Ident, Symbol};
declare_clippy_lint! {
/// ### What it does
@@ -85,7 +85,7 @@ declare_lint_pass!(Lifetimes => [NEEDLESS_LIFETIMES, EXTRA_UNUSED_LIFETIMES]);
impl<'tcx> LateLintPass<'tcx> for Lifetimes {
fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx Item<'_>) {
if let ItemKind::Fn(ref sig, ref generics, id) = item.kind {
- check_fn_inner(cx, sig.decl, Some(id), generics, item.span, true);
+ check_fn_inner(cx, sig.decl, Some(id), None, generics, item.span, true);
}
}
@@ -96,6 +96,7 @@ impl<'tcx> LateLintPass<'tcx> for Lifetimes {
cx,
sig.decl,
Some(id),
+ None,
&item.generics,
item.span,
report_extra_lifetimes,
@@ -105,11 +106,11 @@ impl<'tcx> LateLintPass<'tcx> for Lifetimes {
fn check_trait_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx TraitItem<'_>) {
if let TraitItemKind::Fn(ref sig, ref body) = item.kind {
- let body = match *body {
- TraitFn::Required(_) => None,
- TraitFn::Provided(id) => Some(id),
+ let (body, trait_sig) = match *body {
+ TraitFn::Required(sig) => (None, Some(sig)),
+ TraitFn::Provided(id) => (Some(id), None),
};
- check_fn_inner(cx, sig.decl, body, &item.generics, item.span, true);
+ check_fn_inner(cx, sig.decl, body, trait_sig, &item.generics, item.span, true);
}
}
}
@@ -126,6 +127,7 @@ fn check_fn_inner<'tcx>(
cx: &LateContext<'tcx>,
decl: &'tcx FnDecl<'_>,
body: Option<BodyId>,
+ trait_sig: Option<&[Ident]>,
generics: &'tcx Generics<'_>,
span: Span,
report_extra_lifetimes: bool,
@@ -167,7 +169,7 @@ fn check_fn_inner<'tcx>(
}
}
}
- if could_use_elision(cx, decl, body, generics.params) {
+ if could_use_elision(cx, decl, body, trait_sig, generics.params) {
span_lint(
cx,
NEEDLESS_LIFETIMES,
@@ -181,10 +183,31 @@ fn check_fn_inner<'tcx>(
}
}
+// elision doesn't work for explicit self types, see rust-lang/rust#69064
+fn explicit_self_type<'tcx>(cx: &LateContext<'tcx>, func: &FnDecl<'tcx>, ident: Option<Ident>) -> bool {
+ if_chain! {
+ if let Some(ident) = ident;
+ if ident.name == kw::SelfLower;
+ if !func.implicit_self.has_implicit_self();
+
+ if let Some(self_ty) = func.inputs.first();
+ then {
+ let mut visitor = RefVisitor::new(cx);
+ visitor.visit_ty(self_ty);
+
+ !visitor.all_lts().is_empty()
+ }
+ else {
+ false
+ }
+ }
+}
+
fn could_use_elision<'tcx>(
cx: &LateContext<'tcx>,
func: &'tcx FnDecl<'_>,
body: Option<BodyId>,
+ trait_sig: Option<&[Ident]>,
named_generics: &'tcx [GenericParam<'_>],
) -> bool {
// There are two scenarios where elision works:
@@ -235,11 +258,24 @@ fn could_use_elision<'tcx>(
let input_lts = input_visitor.lts;
let output_lts = output_visitor.lts;
+ if let Some(trait_sig) = trait_sig {
+ if explicit_self_type(cx, func, trait_sig.first().copied()) {
+ return false;
+ }
+ }
+
if let Some(body_id) = body {
+ let body = cx.tcx.hir().body(body_id);
+
+ let first_ident = body.params.first().and_then(|param| param.pat.simple_ident());
+ if explicit_self_type(cx, func, first_ident) {
+ return false;
+ }
+
let mut checker = BodyLifetimeChecker {
lifetimes_used_in_body: false,
};
- checker.visit_expr(&cx.tcx.hir().body(body_id).value);
+ checker.visit_expr(&body.value);
if checker.lifetimes_used_in_body {
return false;
}
diff --git a/tests/ui/needless_lifetimes.rs b/tests/ui/needless_lifetimes.rs
index b07c4a238103..f3eafe8e9279 100644
--- a/tests/ui/needless_lifetimes.rs
+++ b/tests/ui/needless_lifetimes.rs
@@ -1,5 +1,11 @@
#![warn(clippy::needless_lifetimes)]
-#![allow(dead_code, clippy::needless_pass_by_value, clippy::unnecessary_wraps, dyn_drop)]
+#![allow(
+ dead_code,
+ clippy::boxed_local,
+ clippy::needless_pass_by_value,
+ clippy::unnecessary_wraps,
+ dyn_drop
+)]
fn distinct_lifetimes<'a, 'b>(_x: &'a u8, _y: &'b u8, _z: u8) {}
@@ -369,4 +375,47 @@ mod issue6159 {
}
}
+mod issue7296 {
+ use std::rc::Rc;
+ use std::sync::Arc;
+
+ struct Foo;
+ impl Foo {
+ fn implicit<'a>(&'a self) -> &'a () {
+ &()
+ }
+ fn implicit_mut<'a>(&'a mut self) -> &'a () {
+ &()
+ }
+
+ fn explicit<'a>(self: &'a Arc<Self>) -> &'a () {
+ &()
+ }
+ fn explicit_mut<'a>(self: &'a mut Rc<Self>) -> &'a () {
+ &()
+ }
+
+ fn lifetime_elsewhere<'a>(self: Box<Self>, here: &'a ()) -> &'a () {
+ &()
+ }
+ }
+
+ trait Bar {
+ fn implicit<'a>(&'a self) -> &'a ();
+ fn implicit_provided<'a>(&'a self) -> &'a () {
+ &()
+ }
+
+ fn explicit<'a>(self: &'a Arc<Self>) -> &'a ();
+ fn explicit_provided<'a>(self: &'a Arc<Self>) -> &'a () {
+ &()
+ }
+
+ fn lifetime_elsewhere<'a>(self: Box<Self>, here: &'a ()) -> &'a ();
+ fn lifetime_elsewhere_provided<'a>(self: Box<Self>, here: &'a ()) -> &'a () {
+ &()
+ }
+ }
+}
+
fn main() {}
diff --git a/tests/ui/needless_lifetimes.stderr b/tests/ui/needless_lifetimes.stderr
index 4114e6f1832f..ffa152427a97 100644
--- a/tests/ui/needless_lifetimes.stderr
+++ b/tests/ui/needless_lifetimes.stderr
@@ -1,5 +1,5 @@
error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
- --> $DIR/needless_lifetimes.rs:4:1
+ --> $DIR/needless_lifetimes.rs:10:1
|
LL | fn distinct_lifetimes<'a, 'b>(_x: &'a u8, _y: &'b u8, _z: u8) {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -7,148 +7,190 @@ 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
+ --> $DIR/needless_lifetimes.rs:12:1
|
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
+ --> $DIR/needless_lifetimes.rs:22:1
|
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:50:1
+ --> $DIR/needless_lifetimes.rs:56:1
|
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:55:1
+ --> $DIR/needless_lifetimes.rs:61:1
|
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:67:1
+ --> $DIR/needless_lifetimes.rs:73:1
|
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:91:1
+ --> $DIR/needless_lifetimes.rs:97:1
|
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:121:5
+ --> $DIR/needless_lifetimes.rs:127:5
|
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:130:5
+ --> $DIR/needless_lifetimes.rs:136:5
|
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:149:1
+ --> $DIR/needless_lifetimes.rs:155:1
|
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:179:1
+ --> $DIR/needless_lifetimes.rs:185:1
|
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:185:1
+ --> $DIR/needless_lifetimes.rs:191:1
|
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:204:1
+ --> $DIR/needless_lifetimes.rs:210:1
|
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:212:1
+ --> $DIR/needless_lifetimes.rs:218:1
|
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:248:1
+ --> $DIR/needless_lifetimes.rs:254:1
|
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:255:9
+ --> $DIR/needless_lifetimes.rs:261:9
|
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:259:9
+ --> $DIR/needless_lifetimes.rs:265:9
|
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:272:9
+ --> $DIR/needless_lifetimes.rs:278:9
|
LL | fn baz<'a>(&'a self) -> impl Foo + '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:301:5
+ --> $DIR/needless_lifetimes.rs:307:5
|
LL | fn impl_trait_elidable_nested_named_lifetimes<'a>(i: &'a i32, f: impl for<'b> Fn(&'b i32) -> &'b i32) -> &'a i32 {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
- --> $DIR/needless_lifetimes.rs:304:5
+ --> $DIR/needless_lifetimes.rs:310:5
|
LL | fn impl_trait_elidable_nested_anonymous_lifetimes<'a>(i: &'a i32, f: impl Fn(&i32) -> &i32) -> &'a i32 {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
- --> $DIR/needless_lifetimes.rs:313:5
+ --> $DIR/needless_lifetimes.rs:319:5
|
LL | fn generics_elidable<'a, T: Fn(&i32) -> &i32>(i: &'a i32, f: T) -> &'a i32 {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
- --> $DIR/needless_lifetimes.rs:325:5
+ --> $DIR/needless_lifetimes.rs:331:5
|
LL | fn where_clause_elidadable<'a, T>(i: &'a i32, f: T) -> &'a i32
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
- --> $DIR/needless_lifetimes.rs:340:5
+ --> $DIR/needless_lifetimes.rs:346:5
|
LL | fn pointer_fn_elidable<'a>(i: &'a i32, f: fn(&i32) -> &i32) -> &'a i32 {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
- --> $DIR/needless_lifetimes.rs:353:5
+ --> $DIR/needless_lifetimes.rs:359:5
|
LL | fn nested_fn_pointer_3<'a>(_: &'a i32) -> fn(fn(&i32) -> &i32) -> i32 {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
- --> $DIR/needless_lifetimes.rs:356:5
+ --> $DIR/needless_lifetimes.rs:362:5
|
LL | fn nested_fn_pointer_4<'a>(_: &'a i32) -> impl Fn(fn(&i32)) {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-error: aborting due to 25 previous errors
+error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
+ --> $DIR/needless_lifetimes.rs:384:9
+ |
+LL | fn implicit<'a>(&'a self) -> &'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:387:9
+ |
+LL | fn implicit_mut<'a>(&'a mut self) -> &'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:398:9
+ |
+LL | fn lifetime_elsewhere<'a>(self: Box<Self>, here: &'a ()) -> &'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:404:9
+ |
+LL | fn implicit<'a>(&'a self) -> &'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:405:9
+ |
+LL | fn implicit_provided<'a>(&'a self) -> &'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:414:9
+ |
+LL | fn lifetime_elsewhere<'a>(self: Box<Self>, here: &'a ()) -> &'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:415:9
+ |
+LL | fn lifetime_elsewhere_provided<'a>(self: Box<Self>, here: &'a ()) -> &'a () {
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 32 previous errors