2021-03-25 18:29:11 +00:00
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use clippy_utils::diagnostics::{span_lint_and_help, span_lint_and_sugg, span_lint_and_then};
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use clippy_utils::source::{snippet, snippet_with_applicability};
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2021-09-08 14:31:47 +00:00
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use clippy_utils::ty::is_non_aggregate_primitive_type;
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2022-02-25 15:38:06 +00:00
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use clippy_utils::{is_default_equivalent, is_lang_ctor, meets_msrv, msrvs};
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2018-09-16 23:25:33 +00:00
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use if_chain::if_chain;
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2018-12-29 15:04:45 +00:00
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use rustc_errors::Applicability;
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2021-04-22 09:31:13 +00:00
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use rustc_hir::LangItem::OptionNone;
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2020-01-06 16:39:50 +00:00
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use rustc_hir::{BorrowKind, Expr, ExprKind, Mutability, QPath};
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2021-12-04 15:09:15 +00:00
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use rustc_lint::{LateContext, LateLintPass};
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2020-03-30 09:02:14 +00:00
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use rustc_middle::lint::in_external_macro;
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2020-12-20 16:19:49 +00:00
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use rustc_semver::RustcVersion;
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use rustc_session::{declare_tool_lint, impl_lint_pass};
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2020-01-04 10:00:00 +00:00
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use rustc_span::source_map::Span;
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2020-04-10 21:18:03 +00:00
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use rustc_span::symbol::sym;
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2018-09-16 23:25:33 +00:00
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declare_clippy_lint! {
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2021-07-29 10:16:06 +00:00
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/// ### What it does
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/// Checks for `mem::replace()` on an `Option` with
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2019-03-05 16:50:33 +00:00
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/// `None`.
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///
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2021-07-29 10:16:06 +00:00
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/// ### Why is this bad?
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/// `Option` already has the method `take()` for
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2019-03-05 16:50:33 +00:00
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/// taking its current value (Some(..) or None) and replacing it with
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/// `None`.
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///
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2021-07-29 10:16:06 +00:00
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/// ### Example
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2019-03-05 16:50:33 +00:00
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/// ```rust
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2019-03-05 22:23:50 +00:00
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/// use std::mem;
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///
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2019-03-05 16:50:33 +00:00
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/// let mut an_option = Some(0);
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/// let replaced = mem::replace(&mut an_option, None);
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/// ```
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/// Is better expressed with:
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/// ```rust
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/// let mut an_option = Some(0);
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/// let taken = an_option.take();
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/// ```
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2021-12-06 11:33:31 +00:00
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#[clippy::version = "1.31.0"]
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2018-09-16 23:25:33 +00:00
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pub MEM_REPLACE_OPTION_WITH_NONE,
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style,
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"replacing an `Option` with `None` instead of `take()`"
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}
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2019-09-13 16:39:14 +00:00
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declare_clippy_lint! {
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2021-07-29 10:16:06 +00:00
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/// ### What it does
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/// Checks for `mem::replace(&mut _, mem::uninitialized())`
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2019-09-13 16:39:14 +00:00
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/// and `mem::replace(&mut _, mem::zeroed())`.
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///
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2021-07-29 10:16:06 +00:00
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/// ### Why is this bad?
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/// This will lead to undefined behavior even if the
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2019-09-13 16:39:14 +00:00
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/// value is overwritten later, because the uninitialized value may be
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/// observed in the case of a panic.
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///
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2021-07-29 10:16:06 +00:00
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/// ### Example
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2019-09-13 16:39:14 +00:00
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/// ```
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/// use std::mem;
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///# fn may_panic(v: Vec<i32>) -> Vec<i32> { v }
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///
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/// #[allow(deprecated, invalid_value)]
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/// fn myfunc (v: &mut Vec<i32>) {
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/// let taken_v = unsafe { mem::replace(v, mem::uninitialized()) };
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/// let new_v = may_panic(taken_v); // undefined behavior on panic
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/// mem::forget(mem::replace(v, new_v));
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/// }
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/// ```
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///
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/// The [take_mut](https://docs.rs/take_mut) crate offers a sound solution,
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/// at the cost of either lazily creating a replacement value or aborting
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/// on panic, to ensure that the uninitialized value cannot be observed.
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2021-12-06 11:33:31 +00:00
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#[clippy::version = "1.39.0"]
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2019-09-13 16:39:14 +00:00
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pub MEM_REPLACE_WITH_UNINIT,
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correctness,
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"`mem::replace(&mut _, mem::uninitialized())` or `mem::replace(&mut _, mem::zeroed())`"
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}
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2019-12-08 03:10:06 +00:00
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declare_clippy_lint! {
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2021-07-29 10:16:06 +00:00
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/// ### What it does
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/// Checks for `std::mem::replace` on a value of type
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2019-12-08 03:10:06 +00:00
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/// `T` with `T::default()`.
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///
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2021-07-29 10:16:06 +00:00
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/// ### Why is this bad?
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/// `std::mem` module already has the method `take` to
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2019-12-08 03:10:06 +00:00
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/// take the current value and replace it with the default value of that type.
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///
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2021-07-29 10:16:06 +00:00
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/// ### Example
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2019-12-08 03:10:06 +00:00
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/// ```rust
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/// let mut text = String::from("foo");
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/// let replaced = std::mem::replace(&mut text, String::default());
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/// ```
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/// Is better expressed with:
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/// ```rust
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/// let mut text = String::from("foo");
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/// let taken = std::mem::take(&mut text);
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/// ```
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2021-12-06 11:33:31 +00:00
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#[clippy::version = "1.42.0"]
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2019-12-08 03:10:06 +00:00
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pub MEM_REPLACE_WITH_DEFAULT,
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2019-12-19 06:15:55 +00:00
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style,
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2019-12-08 03:10:06 +00:00
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"replacing a value of type `T` with `T::default()` instead of using `std::mem::take`"
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}
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2020-12-20 16:19:49 +00:00
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impl_lint_pass!(MemReplace =>
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2019-12-08 03:10:06 +00:00
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[MEM_REPLACE_OPTION_WITH_NONE, MEM_REPLACE_WITH_UNINIT, MEM_REPLACE_WITH_DEFAULT]);
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2020-06-25 20:41:36 +00:00
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fn check_replace_option_with_none(cx: &LateContext<'_>, src: &Expr<'_>, dest: &Expr<'_>, expr_span: Span) {
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2019-12-22 19:05:19 +00:00
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if let ExprKind::Path(ref replacement_qpath) = src.kind {
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2019-12-08 03:10:06 +00:00
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// Check that second argument is `Option::None`
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2021-04-22 09:31:13 +00:00
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if is_lang_ctor(cx, replacement_qpath, OptionNone) {
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2019-12-08 03:10:06 +00:00
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// Since this is a late pass (already type-checked),
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// and we already know that the second argument is an
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// `Option`, we do not need to check the first
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// argument's type. All that's left is to get
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// replacee's path.
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2019-12-22 19:05:19 +00:00
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let replaced_path = match dest.kind {
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2021-04-08 15:50:13 +00:00
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ExprKind::AddrOf(BorrowKind::Ref, Mutability::Mut, replaced) => {
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if let ExprKind::Path(QPath::Resolved(None, replaced_path)) = replaced.kind {
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2019-12-08 03:10:06 +00:00
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replaced_path
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} else {
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return;
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}
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},
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2021-04-08 15:50:13 +00:00
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ExprKind::Path(QPath::Resolved(None, replaced_path)) => replaced_path,
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2019-12-08 03:10:06 +00:00
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_ => return,
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};
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let mut applicability = Applicability::MachineApplicable;
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span_lint_and_sugg(
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cx,
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MEM_REPLACE_OPTION_WITH_NONE,
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2019-12-22 19:05:19 +00:00
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expr_span,
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2019-12-08 03:10:06 +00:00
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"replacing an `Option` with `None`",
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"consider `Option::take()` instead",
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format!(
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"{}.take()",
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snippet_with_applicability(cx, replaced_path.span, "", &mut applicability)
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),
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applicability,
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);
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}
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}
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}
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2020-06-25 20:41:36 +00:00
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fn check_replace_with_uninit(cx: &LateContext<'_>, src: &Expr<'_>, dest: &Expr<'_>, expr_span: Span) {
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2020-06-23 15:05:22 +00:00
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if_chain! {
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// check if replacement is mem::MaybeUninit::uninit().assume_init()
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2020-07-17 08:47:04 +00:00
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if let Some(method_def_id) = cx.typeck_results().type_dependent_def_id(src.hir_id);
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2020-06-23 15:05:22 +00:00
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if cx.tcx.is_diagnostic_item(sym::assume_init, method_def_id);
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then {
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let mut applicability = Applicability::MachineApplicable;
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span_lint_and_sugg(
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cx,
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MEM_REPLACE_WITH_UNINIT,
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expr_span,
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"replacing with `mem::MaybeUninit::uninit().assume_init()`",
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"consider using",
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format!(
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"std::ptr::read({})",
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snippet_with_applicability(cx, dest.span, "", &mut applicability)
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),
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applicability,
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);
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return;
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}
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}
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if_chain! {
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2021-04-08 15:50:13 +00:00
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if let ExprKind::Call(repl_func, repl_args) = src.kind;
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2020-06-23 15:05:22 +00:00
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if repl_args.is_empty();
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if let ExprKind::Path(ref repl_func_qpath) = repl_func.kind;
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2020-06-26 02:55:23 +00:00
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if let Some(repl_def_id) = cx.qpath_res(repl_func_qpath, repl_func.hir_id).opt_def_id();
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2020-06-23 15:05:22 +00:00
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then {
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if cx.tcx.is_diagnostic_item(sym::mem_uninitialized, repl_def_id) {
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let mut applicability = Applicability::MachineApplicable;
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span_lint_and_sugg(
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cx,
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MEM_REPLACE_WITH_UNINIT,
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expr_span,
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"replacing with `mem::uninitialized()`",
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"consider using",
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format!(
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"std::ptr::read({})",
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snippet_with_applicability(cx, dest.span, "", &mut applicability)
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),
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applicability,
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);
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} else if cx.tcx.is_diagnostic_item(sym::mem_zeroed, repl_def_id) &&
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2020-07-17 08:47:04 +00:00
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!cx.typeck_results().expr_ty(src).is_primitive() {
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2020-06-23 15:05:22 +00:00
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span_lint_and_help(
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cx,
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MEM_REPLACE_WITH_UNINIT,
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expr_span,
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"replacing with `mem::zeroed()`",
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None,
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"consider using a default value or the `take_mut` crate instead",
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);
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2019-12-08 03:10:06 +00:00
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}
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}
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}
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}
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2021-09-08 14:31:47 +00:00
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fn check_replace_with_default(cx: &LateContext<'_>, src: &Expr<'_>, dest: &Expr<'_>, expr_span: Span) {
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// disable lint for primitives
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let expr_type = cx.typeck_results().expr_ty_adjusted(src);
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if is_non_aggregate_primitive_type(expr_type) {
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return;
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}
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// disable lint for Option since it is covered in another lint
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if let ExprKind::Path(q) = &src.kind {
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if is_lang_ctor(cx, q, OptionNone) {
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return;
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2021-03-25 18:29:11 +00:00
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}
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}
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2021-09-08 14:31:47 +00:00
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if is_default_equivalent(cx, src) && !in_external_macro(cx.tcx.sess, expr_span) {
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span_lint_and_then(
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cx,
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MEM_REPLACE_WITH_DEFAULT,
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expr_span,
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"replacing a value of type `T` with `T::default()` is better expressed using `std::mem::take`",
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|diag| {
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2021-12-06 11:33:31 +00:00
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if !expr_span.from_expansion() {
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2021-09-08 14:31:47 +00:00
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let suggestion = format!("std::mem::take({})", snippet(cx, dest.span, ""));
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2021-03-25 18:29:11 +00:00
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2021-09-08 14:31:47 +00:00
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diag.span_suggestion(
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expr_span,
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"consider using",
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suggestion,
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Applicability::MachineApplicable,
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);
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2021-04-08 15:50:13 +00:00
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}
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2021-09-08 14:31:47 +00:00
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},
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);
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2019-12-08 03:10:06 +00:00
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}
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}
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2018-09-16 23:25:33 +00:00
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2020-12-20 16:19:49 +00:00
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pub struct MemReplace {
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msrv: Option<RustcVersion>,
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}
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impl MemReplace {
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#[must_use]
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pub fn new(msrv: Option<RustcVersion>) -> Self {
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Self { msrv }
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}
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}
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2020-06-25 20:41:36 +00:00
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impl<'tcx> LateLintPass<'tcx> for MemReplace {
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fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
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2018-09-16 23:25:33 +00:00
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if_chain! {
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2018-09-18 23:54:01 +00:00
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// Check that `expr` is a call to `mem::replace()`
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2021-04-08 15:50:13 +00:00
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if let ExprKind::Call(func, func_args) = expr.kind;
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2019-09-27 15:16:06 +00:00
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if let ExprKind::Path(ref func_qpath) = func.kind;
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2020-06-26 02:55:23 +00:00
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if let Some(def_id) = cx.qpath_res(func_qpath, func.hir_id).opt_def_id();
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2022-02-25 15:38:06 +00:00
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if cx.tcx.is_diagnostic_item(sym::mem_replace, def_id);
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2021-04-08 15:50:13 +00:00
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if let [dest, src] = func_args;
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2018-09-16 23:25:33 +00:00
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then {
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2019-12-22 19:05:19 +00:00
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check_replace_option_with_none(cx, src, dest, expr.span);
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2020-06-23 15:05:22 +00:00
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check_replace_with_uninit(cx, src, dest, expr.span);
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2022-05-08 11:13:14 +00:00
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if meets_msrv(self.msrv, msrvs::MEM_TAKE) {
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2020-12-20 16:19:49 +00:00
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check_replace_with_default(cx, src, dest, expr.span);
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}
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2018-09-16 23:25:33 +00:00
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}
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}
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}
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2020-12-20 16:19:49 +00:00
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extract_msrv_attr!(LateContext);
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2018-09-16 23:25:33 +00:00
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}
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