117 lines
4.5 KiB
Rust
117 lines
4.5 KiB
Rust
use clippy_utils::diagnostics::span_lint_and_note;
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use clippy_utils::get_parent_node;
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use clippy_utils::is_must_use_func_call;
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use clippy_utils::ty::{is_copy, is_must_use_ty, is_type_lang_item};
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use rustc_hir::{Arm, Expr, ExprKind, LangItem, 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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use rustc_span::sym;
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declare_clippy_lint! {
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/// ### What it does
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/// Checks for calls to `std::mem::drop` with a value that does not implement `Drop`.
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///
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/// ### Why is this bad?
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/// Calling `std::mem::drop` is no different than dropping such a type. A different value may
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/// have been intended.
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///
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/// ### Example
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/// ```rust
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/// struct Foo;
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/// let x = Foo;
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/// std::mem::drop(x);
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/// ```
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#[clippy::version = "1.62.0"]
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pub DROP_NON_DROP,
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suspicious,
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"call to `std::mem::drop` with a value which does not implement `Drop`"
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}
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declare_clippy_lint! {
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/// ### What it does
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/// Checks for calls to `std::mem::forget` with a value that does not implement `Drop`.
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///
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/// ### Why is this bad?
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/// Calling `std::mem::forget` is no different than dropping such a type. A different value may
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/// have been intended.
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///
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/// ### Example
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/// ```rust
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/// struct Foo;
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/// let x = Foo;
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/// std::mem::forget(x);
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/// ```
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#[clippy::version = "1.62.0"]
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pub FORGET_NON_DROP,
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suspicious,
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"call to `std::mem::forget` with a value which does not implement `Drop`"
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}
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const DROP_NON_DROP_SUMMARY: &str = "call to `std::mem::drop` with a value that does not implement `Drop`. \
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Dropping such a type only extends its contained lifetimes";
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const FORGET_NON_DROP_SUMMARY: &str = "call to `std::mem::forget` with a value that does not implement `Drop`. \
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Forgetting such a type is the same as dropping it";
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declare_lint_pass!(DropForgetRef => [
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DROP_NON_DROP,
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FORGET_NON_DROP,
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]);
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impl<'tcx> LateLintPass<'tcx> for DropForgetRef {
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fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
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if let ExprKind::Call(path, [arg]) = expr.kind
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&& let ExprKind::Path(ref qpath) = path.kind
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&& let Some(def_id) = cx.qpath_res(qpath, path.hir_id).opt_def_id()
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&& let Some(fn_name) = cx.tcx.get_diagnostic_name(def_id)
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{
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let arg_ty = cx.typeck_results().expr_ty(arg);
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let is_copy = is_copy(cx, arg_ty);
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let drop_is_single_call_in_arm = is_single_call_in_arm(cx, arg, expr);
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let (lint, msg) = match fn_name {
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// early return for uplifted lints: dropping_references, dropping_copy_types, forgetting_references, forgetting_copy_types
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sym::mem_drop if arg_ty.is_ref() && !drop_is_single_call_in_arm => return,
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sym::mem_forget if arg_ty.is_ref() => return,
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sym::mem_drop if is_copy && !drop_is_single_call_in_arm => return,
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sym::mem_forget if is_copy => return,
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sym::mem_drop if is_type_lang_item(cx, arg_ty, LangItem::ManuallyDrop) => return,
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sym::mem_drop
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if !(arg_ty.needs_drop(cx.tcx, cx.param_env)
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|| is_must_use_func_call(cx, arg)
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|| is_must_use_ty(cx, arg_ty)
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|| drop_is_single_call_in_arm
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) =>
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{
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(DROP_NON_DROP, DROP_NON_DROP_SUMMARY)
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},
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sym::mem_forget if !arg_ty.needs_drop(cx.tcx, cx.param_env) => {
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(FORGET_NON_DROP, FORGET_NON_DROP_SUMMARY)
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},
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_ => return,
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};
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span_lint_and_note(
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cx,
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lint,
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expr.span,
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msg,
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Some(arg.span),
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&format!("argument has type `{arg_ty}`"),
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);
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}
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}
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}
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// dropping returned value of a function like in the following snippet is considered idiomatic, see
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// #9482 for examples match <var> {
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// <pat> => drop(fn_with_side_effect_and_returning_some_value()),
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// ..
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// }
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fn is_single_call_in_arm<'tcx>(cx: &LateContext<'tcx>, arg: &'tcx Expr<'_>, drop_expr: &'tcx Expr<'_>) -> bool {
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if matches!(arg.kind, ExprKind::Call(..) | ExprKind::MethodCall(..)) {
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let parent_node = get_parent_node(cx.tcx, drop_expr.hir_id);
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if let Some(Node::Arm(Arm { body, .. })) = &parent_node {
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return body.hir_id == drop_expr.hir_id;
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}
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}
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false
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}
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