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