60 lines
2.1 KiB
Rust
60 lines
2.1 KiB
Rust
use clippy_utils::diagnostics::span_lint_and_help;
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use clippy_utils::path_res;
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use clippy_utils::ty::is_type_lang_item;
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use rustc_hir::{lang_items, Expr, ExprKind};
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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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use rustc_span::sym;
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declare_clippy_lint! {
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/// ### What it does
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/// Prevents the safe `std::mem::drop` function from being called on `std::mem::ManuallyDrop`.
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///
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/// ### Why is this bad?
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/// The safe `drop` function does not drop the inner value of a `ManuallyDrop`.
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///
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/// ### Known problems
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/// Does not catch cases if the user binds `std::mem::drop`
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/// to a different name and calls it that way.
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///
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/// ### Example
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/// ```rust
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/// struct S;
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/// drop(std::mem::ManuallyDrop::new(S));
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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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/// unsafe {
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/// std::mem::ManuallyDrop::drop(&mut std::mem::ManuallyDrop::new(S));
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/// }
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/// ```
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#[clippy::version = "1.49.0"]
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pub UNDROPPED_MANUALLY_DROPS,
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correctness,
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"use of safe `std::mem::drop` function to drop a std::mem::ManuallyDrop, which will not drop the inner value"
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}
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declare_lint_pass!(UndroppedManuallyDrops => [UNDROPPED_MANUALLY_DROPS]);
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impl<'tcx> LateLintPass<'tcx> for UndroppedManuallyDrops {
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fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
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if_chain! {
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if let ExprKind::Call(fun, [arg_0, ..]) = expr.kind;
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if path_res(cx, fun).opt_def_id() == cx.tcx.get_diagnostic_item(sym::mem_drop);
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let ty = cx.typeck_results().expr_ty(arg_0);
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if is_type_lang_item(cx, ty, lang_items::LangItem::ManuallyDrop);
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then {
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span_lint_and_help(
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cx,
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UNDROPPED_MANUALLY_DROPS,
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expr.span,
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"the inner value of this ManuallyDrop will not be dropped",
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None,
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"to drop a `ManuallyDrop<T>`, use std::mem::ManuallyDrop::drop",
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);
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}
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}
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}
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}
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