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-rw-r--r--src/tools/clippy/clippy_lints/src/drop_forget_ref.rs243
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diff --git a/src/tools/clippy/clippy_lints/src/drop_forget_ref.rs b/src/tools/clippy/clippy_lints/src/drop_forget_ref.rs
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+++ b/src/tools/clippy/clippy_lints/src/drop_forget_ref.rs
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+use clippy_utils::diagnostics::{span_lint_and_help, span_lint_and_note};
+use clippy_utils::is_must_use_func_call;
+use clippy_utils::ty::{is_copy, is_must_use_ty, is_type_lang_item};
+use rustc_hir::{Expr, ExprKind, LangItem};
+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 calls to `std::mem::drop` with a reference
+ /// instead of an owned value.
+ ///
+ /// ### Why is this bad?
+ /// Calling `drop` on a reference will only drop the
+ /// reference itself, which is a no-op. It will not call the `drop` method (from
+ /// the `Drop` trait implementation) on the underlying referenced value, which
+ /// is likely what was intended.
+ ///
+ /// ### Example
+ /// ```ignore
+ /// let mut lock_guard = mutex.lock();
+ /// std::mem::drop(&lock_guard) // Should have been drop(lock_guard), mutex
+ /// // still locked
+ /// operation_that_requires_mutex_to_be_unlocked();
+ /// ```
+ #[clippy::version = "pre 1.29.0"]
+ pub DROP_REF,
+ correctness,
+ "calls to `std::mem::drop` with a reference instead of an owned value"
+}
+
+declare_clippy_lint! {
+ /// ### What it does
+ /// Checks for calls to `std::mem::forget` with a reference
+ /// instead of an owned value.
+ ///
+ /// ### Why is this bad?
+ /// Calling `forget` on a reference will only forget the
+ /// reference itself, which is a no-op. It will not forget the underlying
+ /// referenced
+ /// value, which is likely what was intended.
+ ///
+ /// ### Example
+ /// ```rust
+ /// let x = Box::new(1);
+ /// std::mem::forget(&x) // Should have been forget(x), x will still be dropped
+ /// ```
+ #[clippy::version = "pre 1.29.0"]
+ pub FORGET_REF,
+ correctness,
+ "calls to `std::mem::forget` with a reference instead of an owned value"
+}
+
+declare_clippy_lint! {
+ /// ### What it does
+ /// Checks for calls to `std::mem::drop` with a value
+ /// that derives the Copy trait
+ ///
+ /// ### Why is this bad?
+ /// Calling `std::mem::drop` [does nothing for types that
+ /// implement Copy](https://doc.rust-lang.org/std/mem/fn.drop.html), since the
+ /// value will be copied and moved into the function on invocation.
+ ///
+ /// ### Example
+ /// ```rust
+ /// let x: i32 = 42; // i32 implements Copy
+ /// std::mem::drop(x) // A copy of x is passed to the function, leaving the
+ /// // original unaffected
+ /// ```
+ #[clippy::version = "pre 1.29.0"]
+ pub DROP_COPY,
+ correctness,
+ "calls to `std::mem::drop` with a value that implements Copy"
+}
+
+declare_clippy_lint! {
+ /// ### What it does
+ /// Checks for calls to `std::mem::forget` with a value that
+ /// derives the Copy trait
+ ///
+ /// ### Why is this bad?
+ /// Calling `std::mem::forget` [does nothing for types that
+ /// implement Copy](https://doc.rust-lang.org/std/mem/fn.drop.html) since the
+ /// value will be copied and moved into the function on invocation.
+ ///
+ /// An alternative, but also valid, explanation is that Copy types do not
+ /// implement
+ /// the Drop trait, which means they have no destructors. Without a destructor,
+ /// there
+ /// is nothing for `std::mem::forget` to ignore.
+ ///
+ /// ### Example
+ /// ```rust
+ /// let x: i32 = 42; // i32 implements Copy
+ /// std::mem::forget(x) // A copy of x is passed to the function, leaving the
+ /// // original unaffected
+ /// ```
+ #[clippy::version = "pre 1.29.0"]
+ pub FORGET_COPY,
+ correctness,
+ "calls to `std::mem::forget` with a value that implements Copy"
+}
+
+declare_clippy_lint! {
+ /// ### What it does
+ /// Checks for calls to `std::mem::drop` with a value that does not implement `Drop`.
+ ///
+ /// ### Why is this bad?
+ /// Calling `std::mem::drop` is no different than dropping such a type. A different value may
+ /// have been intended.
+ ///
+ /// ### Example
+ /// ```rust
+ /// struct Foo;
+ /// let x = Foo;
+ /// std::mem::drop(x);
+ /// ```
+ #[clippy::version = "1.62.0"]
+ pub DROP_NON_DROP,
+ suspicious,
+ "call to `std::mem::drop` with a value which does not implement `Drop`"
+}
+
+declare_clippy_lint! {
+ /// ### What it does
+ /// Checks for calls to `std::mem::forget` with a value that does not implement `Drop`.
+ ///
+ /// ### Why is this bad?
+ /// Calling `std::mem::forget` is no different than dropping such a type. A different value may
+ /// have been intended.
+ ///
+ /// ### Example
+ /// ```rust
+ /// struct Foo;
+ /// let x = Foo;
+ /// std::mem::forget(x);
+ /// ```
+ #[clippy::version = "1.62.0"]
+ pub FORGET_NON_DROP,
+ suspicious,
+ "call to `std::mem::forget` with a value which does not implement `Drop`"
+}
+
+declare_clippy_lint! {
+ /// ### What it does
+ /// Prevents the safe `std::mem::drop` function from being called on `std::mem::ManuallyDrop`.
+ ///
+ /// ### Why is this bad?
+ /// The safe `drop` function does not drop the inner value of a `ManuallyDrop`.
+ ///
+ /// ### Known problems
+ /// Does not catch cases if the user binds `std::mem::drop`
+ /// to a different name and calls it that way.
+ ///
+ /// ### Example
+ /// ```rust
+ /// struct S;
+ /// drop(std::mem::ManuallyDrop::new(S));
+ /// ```
+ /// Use instead:
+ /// ```rust
+ /// struct S;
+ /// unsafe {
+ /// std::mem::ManuallyDrop::drop(&mut std::mem::ManuallyDrop::new(S));
+ /// }
+ /// ```
+ #[clippy::version = "1.49.0"]
+ pub UNDROPPED_MANUALLY_DROPS,
+ correctness,
+ "use of safe `std::mem::drop` function to drop a std::mem::ManuallyDrop, which will not drop the inner value"
+}
+
+const DROP_REF_SUMMARY: &str = "calls to `std::mem::drop` with a reference instead of an owned value. \
+ Dropping a reference does nothing";
+const FORGET_REF_SUMMARY: &str = "calls to `std::mem::forget` with a reference instead of an owned value. \
+ Forgetting a reference does nothing";
+const DROP_COPY_SUMMARY: &str = "calls to `std::mem::drop` with a value that implements `Copy`. \
+ Dropping a copy leaves the original intact";
+const FORGET_COPY_SUMMARY: &str = "calls to `std::mem::forget` with a value that implements `Copy`. \
+ Forgetting a copy leaves the original intact";
+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`. \
+ Forgetting such a type is the same as dropping it";
+
+declare_lint_pass!(DropForgetRef => [
+ DROP_REF,
+ FORGET_REF,
+ DROP_COPY,
+ FORGET_COPY,
+ DROP_NON_DROP,
+ FORGET_NON_DROP,
+ UNDROPPED_MANUALLY_DROPS
+]);
+
+impl<'tcx> LateLintPass<'tcx> for DropForgetRef {
+ fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
+ if let ExprKind::Call(path, [arg]) = expr.kind
+ && let ExprKind::Path(ref qpath) = path.kind
+ && let Some(def_id) = cx.qpath_res(qpath, path.hir_id).opt_def_id()
+ && let Some(fn_name) = cx.tcx.get_diagnostic_name(def_id)
+ {
+ let arg_ty = cx.typeck_results().expr_ty(arg);
+ let (lint, msg) = match fn_name {
+ sym::mem_drop if arg_ty.is_ref() => (DROP_REF, DROP_REF_SUMMARY),
+ sym::mem_forget if arg_ty.is_ref() => (FORGET_REF, FORGET_REF_SUMMARY),
+ sym::mem_drop if is_copy(cx, arg_ty) => (DROP_COPY, DROP_COPY_SUMMARY),
+ sym::mem_forget if is_copy(cx, arg_ty) => (FORGET_COPY, FORGET_COPY_SUMMARY),
+ sym::mem_drop if is_type_lang_item(cx, arg_ty, LangItem::ManuallyDrop) => {
+ span_lint_and_help(
+ cx,
+ UNDROPPED_MANUALLY_DROPS,
+ expr.span,
+ "the inner value of this ManuallyDrop will not be dropped",
+ None,
+ "to drop a `ManuallyDrop<T>`, use std::mem::ManuallyDrop::drop",
+ );
+ return;
+ }
+ sym::mem_drop
+ if !(arg_ty.needs_drop(cx.tcx, cx.param_env)
+ || is_must_use_func_call(cx, arg)
+ || is_must_use_ty(cx, arg_ty)) =>
+ {
+ (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)
+ },
+ _ => return,
+ };
+ span_lint_and_note(
+ cx,
+ lint,
+ expr.span,
+ msg,
+ Some(arg.span),
+ &format!("argument has type `{}`", arg_ty),
+ );
+ }
+ }
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-07-26 18:12:52 +0000