66 lines
2.3 KiB
Rust
66 lines
2.3 KiB
Rust
|
use clippy_utils::{diagnostics::span_lint_and_sugg, peel_blocks};
|
||
|
|
use if_chain::if_chain;
|
||
|
|
use rustc_errors::Applicability;
|
||
|
|
use rustc_hir::{Body, ExprKind, Impl, ImplItemKind, Item, ItemKind, Node};
|
||
|
|
use rustc_lint::{LateContext, LateLintPass};
|
||
|
|
use rustc_session::{declare_lint_pass, declare_tool_lint};
|
||
|
|
|
||
|
|
declare_clippy_lint! {
|
||
|
|
/// ### What it does
|
||
|
|
/// Checks for empty `Drop` implementations.
|
||
|
|
///
|
||
|
|
/// ### Why is this bad?
|
||
|
|
/// Empty `Drop` implementations have no effect when dropping an instance of the type. They are
|
||
|
|
/// most likely useless. However, an empty `Drop` implementation prevents a type from being
|
||
|
|
/// destructured, which might be the intention behind adding the implementation as a marker.
|
||
|
|
///
|
||
|
|
/// ### Example
|
||
|
|
/// ```rust
|
||
|
|
/// struct S;
|
||
|
|
///
|
||
|
|
/// impl Drop for S {
|
||
|
|
/// fn drop(&mut self) {}
|
||
|
|
/// }
|
||
|
|
/// ```
|
||
|
|
/// Use instead:
|
||
|
|
/// ```rust
|
||
|
|
/// struct S;
|
||
|
|
/// ```
|
||
|
|
#[clippy::version = "1.61.0"]
|
||
|
|
pub EMPTY_DROP,
|
||
|
|
restriction,
|
||
|
|
"empty `Drop` implementations"
|
||
|
|
}
|
||
|
|
declare_lint_pass!(EmptyDrop => [EMPTY_DROP]);
|
||
|
|
|
||
|
|
impl LateLintPass<'_> for EmptyDrop {
|
||
|
|
fn check_item(&mut self, cx: &LateContext<'_>, item: &Item<'_>) {
|
||
|
|
if_chain! {
|
||
|
|
if let ItemKind::Impl(Impl {
|
||
|
|
of_trait: Some(ref trait_ref),
|
||
|
|
items: [child],
|
||
|
|
..
|
||
|
|
}) = item.kind;
|
||
|
|
if trait_ref.trait_def_id() == cx.tcx.lang_items().drop_trait();
|
||
|
|
if let impl_item_hir = child.id.hir_id();
|
||
|
|
if let Some(Node::ImplItem(impl_item)) = cx.tcx.hir().find(impl_item_hir);
|
||
|
|
if let ImplItemKind::Fn(_, b) = &impl_item.kind;
|
||
|
|
if let Body { value: func_expr, .. } = cx.tcx.hir().body(*b);
|
||
|
|
let func_expr = peel_blocks(func_expr);
|
||
|
|
if let ExprKind::Block(block, _) = func_expr.kind;
|
||
|
|
if block.stmts.is_empty() && block.expr.is_none();
|
||
|
|
then {
|
||
|
|
span_lint_and_sugg(
|
||
|
|
cx,
|
||
|
|
EMPTY_DROP,
|
||
|
|
item.span,
|
||
|
|
"empty drop implementation",
|
||
|
|
"try removing this impl",
|
||
|
|
String::new(),
|
||
|
|
Applicability::MaybeIncorrect
|
||
|
|
);
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|