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Mark let_underscore_drop as uplifted

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This commit is contained in:
Alex Macleod 2022-10-23 13:45:26 +00:00
parent 4f142aa105
commit ff893366c1
15 changed files with 121 additions and 253 deletions
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138
clippy_lints/src/let_underscore.rs
View file

@ -1,7 +1,6 @@
use clippy_utils::diagnostics::span_lint_and_help;
use clippy_utils::ty::{is_must_use_ty, is_type_diagnostic_item, match_type};
use clippy_utils::{is_must_use_func_call, paths};
use if_chain::if_chain;
use rustc_hir::{Local, PatKind};
use rustc_lint::{LateContext, LateLintPass};
use rustc_middle::lint::in_external_macro;
@ -60,45 +59,7 @@ declare_clippy_lint! {
"non-binding let on a synchronization lock"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for `let _ = <expr>`
/// where expr has a type that implements `Drop`
///
/// ### Why is this bad?
/// This statement immediately drops the initializer
/// expression instead of extending its lifetime to the end of the scope, which
/// is often not intended. To extend the expression's lifetime to the end of the
/// scope, use an underscore-prefixed name instead (i.e. _var). If you want to
/// explicitly drop the expression, `std::mem::drop` conveys your intention
/// better and is less error-prone.
///
/// ### Example
/// ```rust
/// # struct DroppableItem;
/// {
/// let _ = DroppableItem;
/// // ^ dropped here
/// /* more code */
/// }
/// ```
///
/// Use instead:
/// ```rust
/// # struct DroppableItem;
/// {
/// let _droppable = DroppableItem;
/// /* more code */
/// // dropped at end of scope
/// }
/// ```
#[clippy::version = "1.50.0"]
pub LET_UNDERSCORE_DROP,
pedantic,
"non-binding let on a type that implements `Drop`"
}
declare_lint_pass!(LetUnderscore => [LET_UNDERSCORE_MUST_USE, LET_UNDERSCORE_LOCK, LET_UNDERSCORE_DROP]);
declare_lint_pass!(LetUnderscore => [LET_UNDERSCORE_MUST_USE, LET_UNDERSCORE_LOCK]);
const SYNC_GUARD_SYMS: [Symbol; 3] = [sym::MutexGuard, sym::RwLockReadGuard, sym::RwLockWriteGuard];
@ -110,64 +71,49 @@ const SYNC_GUARD_PATHS: [&[&str]; 3] = [
impl<'tcx> LateLintPass<'tcx> for LetUnderscore {
fn check_local(&mut self, cx: &LateContext<'_>, local: &Local<'_>) {
if in_external_macro(cx.tcx.sess, local.span) {
return;
}
if !in_external_macro(cx.tcx.sess, local.span)
&& let PatKind::Wild = local.pat.kind
&& let Some(init) = local.init
{
let init_ty = cx.typeck_results().expr_ty(init);
let contains_sync_guard = init_ty.walk().any(|inner| match inner.unpack() {
GenericArgKind::Type(inner_ty) => {
SYNC_GUARD_SYMS
.iter()
.any(|&sym| is_type_diagnostic_item(cx, inner_ty, sym))
|| SYNC_GUARD_PATHS.iter().any(|path| match_type(cx, inner_ty, path))
},
if_chain! {
if let PatKind::Wild = local.pat.kind;
if let Some(init) = local.init;
then {
let init_ty = cx.typeck_results().expr_ty(init);
let contains_sync_guard = init_ty.walk().any(|inner| match inner.unpack() {
GenericArgKind::Type(inner_ty) => {
SYNC_GUARD_SYMS
.iter()
.any(|&sym| is_type_diagnostic_item(cx, inner_ty, sym))
|| SYNC_GUARD_PATHS.iter().any(|path| match_type(cx, inner_ty, path))
},
GenericArgKind::Lifetime(_) | GenericArgKind::Const(_) => false,
});
if contains_sync_guard {
span_lint_and_help(
cx,
LET_UNDERSCORE_LOCK,
local.span,
"non-binding let on a synchronization lock",
None,
"consider using an underscore-prefixed named \
GenericArgKind::Lifetime(_) | GenericArgKind::Const(_) => false,
});
if contains_sync_guard {
span_lint_and_help(
cx,
LET_UNDERSCORE_LOCK,
local.span,
"non-binding let on a synchronization lock",
None,
"consider using an underscore-prefixed named \
binding or dropping explicitly with `std::mem::drop`",
);
} else if init_ty.needs_drop(cx.tcx, cx.param_env) {
span_lint_and_help(
cx,
LET_UNDERSCORE_DROP,
local.span,
"non-binding `let` on a type that implements `Drop`",
None,
"consider using an underscore-prefixed named \
binding or dropping explicitly with `std::mem::drop`",
);
} else if is_must_use_ty(cx, cx.typeck_results().expr_ty(init)) {
span_lint_and_help(
cx,
LET_UNDERSCORE_MUST_USE,
local.span,
"non-binding let on an expression with `#[must_use]` type",
None,
"consider explicitly using expression value",
);
} else if is_must_use_func_call(cx, init) {
span_lint_and_help(
cx,
LET_UNDERSCORE_MUST_USE,
local.span,
"non-binding let on a result of a `#[must_use]` function",
None,
"consider explicitly using function result",
);
}
);
} else if is_must_use_ty(cx, cx.typeck_results().expr_ty(init)) {
span_lint_and_help(
cx,
LET_UNDERSCORE_MUST_USE,
local.span,
"non-binding let on an expression with `#[must_use]` type",
None,
"consider explicitly using expression value",
);
} else if is_must_use_func_call(cx, init) {
span_lint_and_help(
cx,
LET_UNDERSCORE_MUST_USE,
local.span,
"non-binding let on a result of a `#[must_use]` function",
None,
"consider explicitly using function result",
);
}
}
}

1
clippy_lints/src/lib.register_lints.rs
View file

@ -214,7 +214,6 @@ store.register_lints(&[
len_zero::LEN_WITHOUT_IS_EMPTY,
len_zero::LEN_ZERO,
let_if_seq::USELESS_LET_IF_SEQ,
let_underscore::LET_UNDERSCORE_DROP,
let_underscore::LET_UNDERSCORE_LOCK,
let_underscore::LET_UNDERSCORE_MUST_USE,
lifetimes::EXTRA_UNUSED_LIFETIMES,

1
clippy_lints/src/lib.register_pedantic.rs
View file

@ -39,7 +39,6 @@ store.register_group(true, "clippy::pedantic", Some("clippy_pedantic"), vec![
LintId::of(items_after_statements::ITEMS_AFTER_STATEMENTS),
LintId::of(iter_not_returning_iterator::ITER_NOT_RETURNING_ITERATOR),
LintId::of(large_stack_arrays::LARGE_STACK_ARRAYS),
LintId::of(let_underscore::LET_UNDERSCORE_DROP),
LintId::of(literal_representation::LARGE_DIGIT_GROUPS),
LintId::of(literal_representation::UNREADABLE_LITERAL),
LintId::of(loops::EXPLICIT_INTO_ITER_LOOP),

5
clippy_lints/src/renamed_lints.rs
View file

@ -11,8 +11,6 @@ pub static RENAMED_LINTS: &[(&str, &str)] = &[
("clippy::disallowed_method", "clippy::disallowed_methods"),
("clippy::disallowed_type", "clippy::disallowed_types"),
("clippy::eval_order_dependence", "clippy::mixed_read_write_in_expression"),
("clippy::for_loop_over_option", "for_loops_over_fallibles"),
("clippy::for_loop_over_result", "for_loops_over_fallibles"),
("clippy::identity_conversion", "clippy::useless_conversion"),
("clippy::if_let_some_result", "clippy::match_result_ok"),
("clippy::logic_bug", "clippy::overly_complex_bool_expr"),
@ -31,10 +29,13 @@ pub static RENAMED_LINTS: &[(&str, &str)] = &[
("clippy::to_string_in_display", "clippy::recursive_format_impl"),
("clippy::zero_width_space", "clippy::invisible_characters"),
("clippy::drop_bounds", "drop_bounds"),
("clippy::for_loop_over_option", "for_loops_over_fallibles"),
("clippy::for_loop_over_result", "for_loops_over_fallibles"),
("clippy::for_loops_over_fallibles", "for_loops_over_fallibles"),
("clippy::into_iter_on_array", "array_into_iter"),
("clippy::invalid_atomic_ordering", "invalid_atomic_ordering"),
("clippy::invalid_ref", "invalid_value"),
("clippy::let_underscore_drop", "let_underscore_drop"),
("clippy::mem_discriminant_non_enum", "enum_intrinsics_non_enums"),
("clippy::panic_params", "non_fmt_panics"),
("clippy::positional_named_format_parameters", "named_arguments_used_positionally"),