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Auto merge of #10996 - Centri3:mem_forget, r=xFrednet

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Lint `mem_forget` if any fields are `Drop`

Closes #9298
I think this way of doing it (`needs_drop`) should be fine.

---

changelog: Enhancement: [`mem_forget`]: Now lints on types with fields that implement `Drop`
[#10996](https://github.com/rust-lang/rust-clippy/pull/10996)
This commit is contained in:
bors 2023-06-25 09:40:13 +00:00
commit 78e36d9f53
6 changed files with 64 additions and 58 deletions
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2
clippy_lints/src/declared_lints.rs
View file

@ -140,6 +140,7 @@ pub(crate) static LINTS: &[&crate::LintInfo] = &[
crate::double_parens::DOUBLE_PARENS_INFO,
crate::drop_forget_ref::DROP_NON_DROP_INFO,
crate::drop_forget_ref::FORGET_NON_DROP_INFO,
crate::drop_forget_ref::MEM_FORGET_INFO,
crate::drop_forget_ref::UNDROPPED_MANUALLY_DROPS_INFO,
crate::duplicate_mod::DUPLICATE_MOD_INFO,
crate::else_if_without_else::ELSE_IF_WITHOUT_ELSE_INFO,
@ -310,7 +311,6 @@ pub(crate) static LINTS: &[&crate::LintInfo] = &[
crate::matches::TRY_ERR_INFO,
crate::matches::WILDCARD_ENUM_MATCH_ARM_INFO,
crate::matches::WILDCARD_IN_OR_PATTERNS_INFO,
crate::mem_forget::MEM_FORGET_INFO,
crate::mem_replace::MEM_REPLACE_OPTION_WITH_NONE_INFO,
crate::mem_replace::MEM_REPLACE_WITH_DEFAULT_INFO,
crate::mem_replace::MEM_REPLACE_WITH_UNINIT_INFO,

54
clippy_lints/src/drop_forget_ref.rs
View file

@ -6,6 +6,7 @@ use rustc_hir::{Arm, Expr, ExprKind, LangItem, Node};
use rustc_lint::{LateContext, LateLintPass};
use rustc_session::{declare_lint_pass, declare_tool_lint};
use rustc_span::sym;
use std::borrow::Cow;
declare_clippy_lint! {
/// ### What it does
@ -76,6 +77,27 @@ declare_clippy_lint! {
"use of safe `std::mem::drop` function to drop a std::mem::ManuallyDrop, which will not drop the inner value"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for usage of `std::mem::forget(t)` where `t` is
/// `Drop` or has a field that implements `Drop`.
///
/// ### Why is this bad?
/// `std::mem::forget(t)` prevents `t` from running its
/// destructor, possibly causing leaks.
///
/// ### Example
/// ```rust
/// # use std::mem;
/// # use std::rc::Rc;
/// mem::forget(Rc::new(55))
/// ```
#[clippy::version = "pre 1.29.0"]
pub MEM_FORGET,
restriction,
"`mem::forget` usage on `Drop` types, likely to cause memory leaks"
}
const DROP_NON_DROP_SUMMARY: &str = "call to `std::mem::drop` with a value that does not implement `Drop`. \
Dropping such a type only extends its contained lifetimes";
const FORGET_NON_DROP_SUMMARY: &str = "call to `std::mem::forget` with a value that does not implement `Drop`. \
@ -84,7 +106,8 @@ const FORGET_NON_DROP_SUMMARY: &str = "call to `std::mem::forget` with a value t
declare_lint_pass!(DropForgetRef => [
DROP_NON_DROP,
FORGET_NON_DROP,
UNDROPPED_MANUALLY_DROPS
UNDROPPED_MANUALLY_DROPS,
MEM_FORGET,
]);
impl<'tcx> LateLintPass<'tcx> for DropForgetRef {
@ -97,7 +120,7 @@ impl<'tcx> LateLintPass<'tcx> for DropForgetRef {
let arg_ty = cx.typeck_results().expr_ty(arg);
let is_copy = is_copy(cx, arg_ty);
let drop_is_single_call_in_arm = is_single_call_in_arm(cx, arg, expr);
let (lint, msg) = match fn_name {
let (lint, msg, note_span) = match fn_name {
// early return for uplifted lints: dropping_references, dropping_copy_types, forgetting_references, forgetting_copy_types
sym::mem_drop if arg_ty.is_ref() && !drop_is_single_call_in_arm => return,
sym::mem_forget if arg_ty.is_ref() => return,
@ -121,19 +144,34 @@ impl<'tcx> LateLintPass<'tcx> for DropForgetRef {
|| drop_is_single_call_in_arm
) =>
{
(DROP_NON_DROP, DROP_NON_DROP_SUMMARY)
},
sym::mem_forget if !arg_ty.needs_drop(cx.tcx, cx.param_env) => {
(FORGET_NON_DROP, FORGET_NON_DROP_SUMMARY)
(DROP_NON_DROP, DROP_NON_DROP_SUMMARY.into(), Some(arg.span))
},
sym::mem_forget => {
if arg_ty.needs_drop(cx.tcx, cx.param_env) {
(
MEM_FORGET,
Cow::Owned(format!(
"usage of `mem::forget` on {}",
if arg_ty.ty_adt_def().map_or(false, |def| def.has_dtor(cx.tcx)) {
"`Drop` type"
} else {
"type with `Drop` fields"
}
)),
None,
)
} else {
(FORGET_NON_DROP, FORGET_NON_DROP_SUMMARY.into(), Some(arg.span))
}
}
_ => return,
};
span_lint_and_note(
cx,
lint,
expr.span,
msg,
Some(arg.span),
&msg,
note_span,
&format!("argument has type `{arg_ty}`"),
);
}

2
clippy_lints/src/lib.rs
View file

@ -196,7 +196,6 @@ mod manual_strip;
mod map_unit_fn;
mod match_result_ok;
mod matches;
mod mem_forget;
mod mem_replace;
mod methods;
mod min_ident_chars;
@ -744,7 +743,6 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
let missing_docs_in_crate_items = conf.missing_docs_in_crate_items;
store.register_late_pass(move |_| Box::new(doc::DocMarkdown::new(doc_valid_idents.clone())));
store.register_late_pass(|_| Box::new(neg_multiply::NegMultiply));
store.register_late_pass(|_| Box::new(mem_forget::MemForget));
store.register_late_pass(|_| Box::new(let_if_seq::LetIfSeq));
store.register_late_pass(|_| Box::new(mixed_read_write_in_expression::EvalOrderDependence));
store.register_late_pass(move |_| Box::new(missing_doc::MissingDoc::new(missing_docs_in_crate_items)));

46
clippy_lints/src/mem_forget.rs
View file

@ -1,46 +0,0 @@
use clippy_utils::diagnostics::span_lint;
use rustc_hir::{Expr, ExprKind};
use rustc_lint::{LateContext, LateLintPass};
use rustc_session::{declare_lint_pass, declare_tool_lint};
use rustc_span::sym;
declare_clippy_lint! {
/// ### What it does
/// Checks for usage of `std::mem::forget(t)` where `t` is
/// `Drop`.
///
/// ### Why is this bad?
/// `std::mem::forget(t)` prevents `t` from running its
/// destructor, possibly causing leaks.
///
/// ### Example
/// ```rust
/// # use std::mem;
/// # use std::rc::Rc;
/// mem::forget(Rc::new(55))
/// ```
#[clippy::version = "pre 1.29.0"]
pub MEM_FORGET,
restriction,
"`mem::forget` usage on `Drop` types, likely to cause memory leaks"
}
declare_lint_pass!(MemForget => [MEM_FORGET]);
impl<'tcx> LateLintPass<'tcx> for MemForget {
fn check_expr(&mut self, cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) {
if let ExprKind::Call(path_expr, [ref first_arg, ..]) = e.kind {
if let ExprKind::Path(ref qpath) = path_expr.kind {
if let Some(def_id) = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id() {
if cx.tcx.is_diagnostic_item(sym::mem_forget, def_id) {
let forgot_ty = cx.typeck_results().expr_ty(first_arg);
if forgot_ty.ty_adt_def().map_or(false, |def| def.has_dtor(cx.tcx)) {
span_lint(cx, MEM_FORGET, e.span, "usage of `mem::forget` on `Drop` type");
}
}
}
}
}
}
}

3
tests/ui/mem_forget.rs
View file

@ -19,5 +19,8 @@ fn main() {
let eight: Vec<i32> = vec![8];
forgetSomething(eight);
let string = String::new();
std::mem::forget(string);
std::mem::forget(7);
}

15
tests/ui/mem_forget.stderr
View file

@ -4,6 +4,7 @@ error: usage of `mem::forget` on `Drop` type
LL | memstuff::forget(six);
| ^^^^^^^^^^^^^^^^^^^^^
|
= note: argument has type `std::sync::Arc<i32>`
= note: `-D clippy::mem-forget` implied by `-D warnings`
error: usage of `mem::forget` on `Drop` type
@ -11,12 +12,24 @@ error: usage of `mem::forget` on `Drop` type
|
LL | std::mem::forget(seven);
| ^^^^^^^^^^^^^^^^^^^^^^^
|
= note: argument has type `std::rc::Rc<i32>`
error: usage of `mem::forget` on `Drop` type
--> $DIR/mem_forget.rs:20:5
|
LL | forgetSomething(eight);
| ^^^^^^^^^^^^^^^^^^^^^^
|
= note: argument has type `std::vec::Vec<i32>`
error: aborting due to 3 previous errors
error: usage of `mem::forget` on type with `Drop` fields
--> $DIR/mem_forget.rs:23:5
|
LL | std::mem::forget(string);
| ^^^^^^^^^^^^^^^^^^^^^^^^
|
= note: argument has type `std::string::String`
error: aborting due to 4 previous errors