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Auto merge of #13294 - WeiTheShinobi:new_lint_used_underscore_items, r=llogiq

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Add new lint: `used_underscore_items`

Closes #13260

---

changelog: new [`used_underscore_items`] lint against using items with a single leading underscore
This commit is contained in:
bors 2024-08-27 10:59:31 +00:00
commit 603d5a19c9
7 changed files with 334 additions and 56 deletions
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1
CHANGELOG.md
View file

@ -6013,6 +6013,7 @@ Released 2018-09-13
[`use_debug`]: https://rust-lang.github.io/rust-clippy/master/index.html#use_debug
[`use_self`]: https://rust-lang.github.io/rust-clippy/master/index.html#use_self
[`used_underscore_binding`]: https://rust-lang.github.io/rust-clippy/master/index.html#used_underscore_binding
[`used_underscore_items`]: https://rust-lang.github.io/rust-clippy/master/index.html#used_underscore_items
[`useless_asref`]: https://rust-lang.github.io/rust-clippy/master/index.html#useless_asref
[`useless_attribute`]: https://rust-lang.github.io/rust-clippy/master/index.html#useless_attribute
[`useless_conversion`]: https://rust-lang.github.io/rust-clippy/master/index.html#useless_conversion

1
clippy_lints/src/declared_lints.rs
View file

@ -486,6 +486,7 @@ pub static LINTS: &[&crate::LintInfo] = &[
crate::misc::SHORT_CIRCUIT_STATEMENT_INFO,
crate::misc::TOPLEVEL_REF_ARG_INFO,
crate::misc::USED_UNDERSCORE_BINDING_INFO,
crate::misc::USED_UNDERSCORE_ITEMS_INFO,
crate::misc_early::BUILTIN_TYPE_SHADOW_INFO,
crate::misc_early::DOUBLE_NEG_INFO,
crate::misc_early::DUPLICATE_UNDERSCORE_ARGUMENT_INFO,

182
clippy_lints/src/misc.rs
View file

@ -7,6 +7,7 @@ use clippy_utils::{
};
use rustc_errors::Applicability;
use rustc_hir::def::Res;
use rustc_hir::def_id::LOCAL_CRATE;
use rustc_hir::intravisit::FnKind;
use rustc_hir::{
BinOpKind, BindingMode, Body, ByRef, Expr, ExprKind, FnDecl, Mutability, PatKind, QPath, Stmt, StmtKind,
@ -80,6 +81,45 @@ declare_clippy_lint! {
"using a binding which is prefixed with an underscore"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for the use of item with a single leading
/// underscore.
///
/// ### Why is this bad?
/// A single leading underscore is usually used to indicate
/// that a item will not be used. Using such a item breaks this
/// expectation.
///
/// ### Example
/// ```no_run
/// fn _foo() {}
///
/// struct _FooStruct {}
///
/// fn main() {
/// _foo();
/// let _ = _FooStruct{};
/// }
/// ```
///
/// Use instead:
/// ```no_run
/// fn foo() {}
///
/// struct FooStruct {}
///
/// fn main() {
/// foo();
/// let _ = FooStruct{};
/// }
/// ```
#[clippy::version = "pre 1.29.0"]
pub USED_UNDERSCORE_ITEMS,
pedantic,
"using a item which is prefixed with an underscore"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for the use of short circuit boolean conditions as
@ -104,6 +144,7 @@ declare_clippy_lint! {
declare_lint_pass!(LintPass => [
TOPLEVEL_REF_ARG,
USED_UNDERSCORE_BINDING,
USED_UNDERSCORE_ITEMS,
SHORT_CIRCUIT_STATEMENT,
]);
@ -205,51 +246,104 @@ impl<'tcx> LateLintPass<'tcx> for LintPass {
{
return;
}
let (definition_hir_id, ident) = match expr.kind {
ExprKind::Path(ref qpath) => {
if let QPath::Resolved(None, path) = qpath
&& let Res::Local(id) = path.res
&& is_used(cx, expr)
{
(id, last_path_segment(qpath).ident)
} else {
return;
}
},
ExprKind::Field(recv, ident) => {
if let Some(adt_def) = cx.typeck_results().expr_ty_adjusted(recv).ty_adt_def()
&& let Some(field) = adt_def.all_fields().find(|field| field.name == ident.name)
&& let Some(local_did) = field.did.as_local()
&& !cx.tcx.type_of(field.did).skip_binder().is_phantom_data()
{
(cx.tcx.local_def_id_to_hir_id(local_did), ident)
} else {
return;
}
},
_ => return,
};
let name = ident.name.as_str();
if name.starts_with('_')
&& !name.starts_with("__")
&& let definition_span = cx.tcx.hir().span(definition_hir_id)
&& !definition_span.from_expansion()
&& !fulfill_or_allowed(cx, USED_UNDERSCORE_BINDING, [expr.hir_id, definition_hir_id])
{
span_lint_and_then(
cx,
USED_UNDERSCORE_BINDING,
expr.span,
format!(
"used binding `{name}` which is prefixed with an underscore. A leading \
underscore signals that a binding will not be used"
),
|diag| {
diag.span_note(definition_span, format!("`{name}` is defined here"));
},
);
}
used_underscore_binding(cx, expr);
used_underscore_items(cx, expr);
}
}
fn used_underscore_items<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
let (def_id, ident) = match expr.kind {
ExprKind::Call(func, ..) => {
if let ExprKind::Path(QPath::Resolved(.., path)) = func.kind
&& let Some(last_segment) = path.segments.last()
&& let Res::Def(_, def_id) = last_segment.res
{
(def_id, last_segment.ident)
} else {
return;
}
},
ExprKind::MethodCall(path, ..) => {
if let Some(def_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id) {
(def_id, path.ident)
} else {
return;
}
},
ExprKind::Struct(QPath::Resolved(_, path), ..) => {
if let Some(last_segment) = path.segments.last()
&& let Res::Def(_, def_id) = last_segment.res
{
(def_id, last_segment.ident)
} else {
return;
}
},
_ => return,
};
let name = ident.name.as_str();
let definition_span = cx.tcx.def_span(def_id);
if name.starts_with('_')
&& !name.starts_with("__")
&& !definition_span.from_expansion()
&& def_id.krate == LOCAL_CRATE
{
span_lint_and_then(
cx,
USED_UNDERSCORE_ITEMS,
expr.span,
"used underscore-prefixed item".to_string(),
|diag| {
diag.span_note(definition_span, "item is defined here".to_string());
},
);
}
}
fn used_underscore_binding<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
let (definition_hir_id, ident) = match expr.kind {
ExprKind::Path(ref qpath) => {
if let QPath::Resolved(None, path) = qpath
&& let Res::Local(id) = path.res
&& is_used(cx, expr)
{
(id, last_path_segment(qpath).ident)
} else {
return;
}
},
ExprKind::Field(recv, ident) => {
if let Some(adt_def) = cx.typeck_results().expr_ty_adjusted(recv).ty_adt_def()
&& let Some(field) = adt_def.all_fields().find(|field| field.name == ident.name)
&& let Some(local_did) = field.did.as_local()
&& !cx.tcx.type_of(field.did).skip_binder().is_phantom_data()
{
(cx.tcx.local_def_id_to_hir_id(local_did), ident)
} else {
return;
}
},
_ => return,
};
let name = ident.name.as_str();
if name.starts_with('_')
&& !name.starts_with("__")
&& let definition_span = cx.tcx.hir().span(definition_hir_id)
&& !definition_span.from_expansion()
&& !fulfill_or_allowed(cx, USED_UNDERSCORE_BINDING, [expr.hir_id, definition_hir_id])
{
span_lint_and_then(
cx,
USED_UNDERSCORE_BINDING,
expr.span,
"used underscore-prefixed binding".to_string(),
|diag| {
diag.span_note(definition_span, "binding is defined here".to_string());
},
);
}
}

7
tests/ui/auxiliary/external_item.rs Normal file
View file

@ -0,0 +1,7 @@
pub struct _ExternalStruct {}
impl _ExternalStruct {
pub fn _foo(self) {}
}
pub fn _exernal_foo() {}

24
tests/ui/used_underscore_binding.stderr
View file

@ -1,10 +1,10 @@
error: used binding `_foo` which is prefixed with an underscore. A leading underscore signals that a binding will not be used
error: used underscore-prefixed binding
--> tests/ui/used_underscore_binding.rs:23:5
|
LL | _foo + 1
| ^^^^
|
note: `_foo` is defined here
note: binding is defined here
--> tests/ui/used_underscore_binding.rs:22:22
|
LL | fn prefix_underscore(_foo: u32) -> u32 {
@ -12,61 +12,61 @@ LL | fn prefix_underscore(_foo: u32) -> u32 {
= note: `-D clippy::used-underscore-binding` implied by `-D warnings`
= help: to override `-D warnings` add `#[allow(clippy::used_underscore_binding)]`
error: used binding `_foo` which is prefixed with an underscore. A leading underscore signals that a binding will not be used
error: used underscore-prefixed binding
--> tests/ui/used_underscore_binding.rs:28:20
|
LL | println!("{}", _foo);
| ^^^^
|
note: `_foo` is defined here
note: binding is defined here
--> tests/ui/used_underscore_binding.rs:27:24
|
LL | fn in_macro_or_desugar(_foo: u32) {
| ^^^^
error: used binding `_foo` which is prefixed with an underscore. A leading underscore signals that a binding will not be used
error: used underscore-prefixed binding
--> tests/ui/used_underscore_binding.rs:29:16
|
LL | assert_eq!(_foo, _foo);
| ^^^^
|
note: `_foo` is defined here
note: binding is defined here
--> tests/ui/used_underscore_binding.rs:27:24
|
LL | fn in_macro_or_desugar(_foo: u32) {
| ^^^^
error: used binding `_foo` which is prefixed with an underscore. A leading underscore signals that a binding will not be used
error: used underscore-prefixed binding
--> tests/ui/used_underscore_binding.rs:29:22
|
LL | assert_eq!(_foo, _foo);
| ^^^^
|
note: `_foo` is defined here
note: binding is defined here
--> tests/ui/used_underscore_binding.rs:27:24
|
LL | fn in_macro_or_desugar(_foo: u32) {
| ^^^^
error: used binding `_underscore_field` which is prefixed with an underscore. A leading underscore signals that a binding will not be used
error: used underscore-prefixed binding
--> tests/ui/used_underscore_binding.rs:42:5
|
LL | s._underscore_field += 1;
| ^^^^^^^^^^^^^^^^^^^
|
note: `_underscore_field` is defined here
note: binding is defined here
--> tests/ui/used_underscore_binding.rs:36:5
|
LL | _underscore_field: u32,
| ^^^^^^^^^^^^^^^^^^^^^^
error: used binding `_i` which is prefixed with an underscore. A leading underscore signals that a binding will not be used
error: used underscore-prefixed binding
--> tests/ui/used_underscore_binding.rs:103:16
|
LL | uses_i(_i);
| ^^
|
note: `_i` is defined here
note: binding is defined here
--> tests/ui/used_underscore_binding.rs:102:13
|
LL | let _i = 5;

63
tests/ui/used_underscore_items.rs Normal file
View file

@ -0,0 +1,63 @@
//@aux-build:external_item.rs
#![allow(unused)]
#![warn(clippy::used_underscore_items)]
extern crate external_item;
// should not lint macro
macro_rules! macro_wrap_func {
() => {
fn _marco_foo() {}
};
}
macro_wrap_func!();
struct _FooStruct {}
impl _FooStruct {
fn _method_call(self) {}
}
fn _foo1() {}
fn _foo2() -> i32 {
0
}
mod a {
pub mod b {
pub mod c {
pub fn _foo3() {}
pub struct _FooStruct2 {}
impl _FooStruct2 {
pub fn _method_call(self) {}
}
}
}
}
fn main() {
_foo1();
let _ = _foo2();
a::b::c::_foo3();
let _ = &_FooStruct {};
let _ = _FooStruct {};
let foo_struct = _FooStruct {};
foo_struct._method_call();
let foo_struct2 = a::b::c::_FooStruct2 {};
foo_struct2._method_call();
}
// should not lint exteranl crate.
// user cannot control how others name their items
fn external_item_call() {
let foo_struct3 = external_item::_ExternalStruct {};
foo_struct3._foo();
external_item::_exernal_foo();
}

112
tests/ui/used_underscore_items.stderr Normal file
View file

@ -0,0 +1,112 @@
error: used underscore-prefixed item
--> tests/ui/used_underscore_items.rs:43:5
|
LL | _foo1();
| ^^^^^^^
|
note: item is defined here
--> tests/ui/used_underscore_items.rs:22:1
|
LL | fn _foo1() {}
| ^^^^^^^^^^
= note: `-D clippy::used-underscore-items` implied by `-D warnings`
= help: to override `-D warnings` add `#[allow(clippy::used_underscore_items)]`
error: used underscore-prefixed item
--> tests/ui/used_underscore_items.rs:44:13
|
LL | let _ = _foo2();
| ^^^^^^^
|
note: item is defined here
--> tests/ui/used_underscore_items.rs:24:1
|
LL | fn _foo2() -> i32 {
| ^^^^^^^^^^^^^^^^^
error: used underscore-prefixed item
--> tests/ui/used_underscore_items.rs:45:5
|
LL | a::b::c::_foo3();
| ^^^^^^^^^^^^^^^^
|
note: item is defined here
--> tests/ui/used_underscore_items.rs:31:13
|
LL | pub fn _foo3() {}
| ^^^^^^^^^^^^^^
error: used underscore-prefixed item
--> tests/ui/used_underscore_items.rs:46:14
|
LL | let _ = &_FooStruct {};
| ^^^^^^^^^^^^^
|
note: item is defined here
--> tests/ui/used_underscore_items.rs:16:1
|
LL | struct _FooStruct {}
| ^^^^^^^^^^^^^^^^^
error: used underscore-prefixed item
--> tests/ui/used_underscore_items.rs:47:13
|
LL | let _ = _FooStruct {};
| ^^^^^^^^^^^^^
|
note: item is defined here
--> tests/ui/used_underscore_items.rs:16:1
|
LL | struct _FooStruct {}
| ^^^^^^^^^^^^^^^^^
error: used underscore-prefixed item
--> tests/ui/used_underscore_items.rs:49:22
|
LL | let foo_struct = _FooStruct {};
| ^^^^^^^^^^^^^
|
note: item is defined here
--> tests/ui/used_underscore_items.rs:16:1
|
LL | struct _FooStruct {}
| ^^^^^^^^^^^^^^^^^
error: used underscore-prefixed item
--> tests/ui/used_underscore_items.rs:50:5
|
LL | foo_struct._method_call();
| ^^^^^^^^^^^^^^^^^^^^^^^^^
|
note: item is defined here
--> tests/ui/used_underscore_items.rs:19:5
|
LL | fn _method_call(self) {}
| ^^^^^^^^^^^^^^^^^^^^^
error: used underscore-prefixed item
--> tests/ui/used_underscore_items.rs:52:23
|
LL | let foo_struct2 = a::b::c::_FooStruct2 {};
| ^^^^^^^^^^^^^^^^^^^^^^^
|
note: item is defined here
--> tests/ui/used_underscore_items.rs:33:13
|
LL | pub struct _FooStruct2 {}
| ^^^^^^^^^^^^^^^^^^^^^^
error: used underscore-prefixed item
--> tests/ui/used_underscore_items.rs:53:5
|
LL | foo_struct2._method_call();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^
|
note: item is defined here
--> tests/ui/used_underscore_items.rs:36:17
|
LL | pub fn _method_call(self) {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^
error: aborting due to 9 previous errors