1 use clippy_utils::diagnostics::span_lint_and_help;
2 use clippy_utils::ty::is_type_lang_item;
3 use clippy_utils::{match_function_call, paths};
4 use rustc_hir::{lang_items, Expr};
5 use rustc_lint::{LateContext, LateLintPass};
6 use rustc_session::{declare_lint_pass, declare_tool_lint};
10 /// Prevents the safe `std::mem::drop` function from being called on `std::mem::ManuallyDrop`.
12 /// ### Why is this bad?
13 /// The safe `drop` function does not drop the inner value of a `ManuallyDrop`.
15 /// ### Known problems
16 /// Does not catch cases if the user binds `std::mem::drop`
17 /// to a different name and calls it that way.
22 /// drop(std::mem::ManuallyDrop::new(S));
28 /// std::mem::ManuallyDrop::drop(&mut std::mem::ManuallyDrop::new(S));
31 pub UNDROPPED_MANUALLY_DROPS,
33 "use of safe `std::mem::drop` function to drop a std::mem::ManuallyDrop, which will not drop the inner value"
36 declare_lint_pass!(UndroppedManuallyDrops => [UNDROPPED_MANUALLY_DROPS]);
38 impl LateLintPass<'tcx> for UndroppedManuallyDrops {
39 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
40 if let Some([arg_0, ..]) = match_function_call(cx, expr, &paths::DROP) {
41 let ty = cx.typeck_results().expr_ty(arg_0);
42 if is_type_lang_item(cx, ty, lang_items::LangItem::ManuallyDrop) {
45 UNDROPPED_MANUALLY_DROPS,
47 "the inner value of this ManuallyDrop will not be dropped",
49 "to drop a `ManuallyDrop<T>`, use std::mem::ManuallyDrop::drop",