247 lines
8.8 KiB
Rust
247 lines
8.8 KiB
Rust
use clippy_config::Conf;
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use clippy_config::msrvs::{self, Msrv};
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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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use clippy_utils::sugg::Sugg;
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use clippy_utils::ty::is_non_aggregate_primitive_type;
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use clippy_utils::{
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is_default_equivalent, is_expr_used_or_unified, is_res_lang_ctor, path_res, peel_ref_operators, std_or_core,
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};
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use rustc_errors::Applicability;
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use rustc_hir::LangItem::OptionNone;
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use rustc_hir::{Expr, ExprKind};
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use rustc_lint::{LateContext, LateLintPass};
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use rustc_middle::lint::in_external_macro;
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use rustc_session::impl_lint_pass;
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use rustc_span::Span;
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use rustc_span::symbol::sym;
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declare_clippy_lint! {
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/// ### What it does
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/// Checks for `mem::replace()` on an `Option` with
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/// `None`.
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///
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/// ### Why is this bad?
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/// `Option` already has the method `take()` for
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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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/// ### Example
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/// ```no_run
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/// use std::mem;
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///
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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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/// ```no_run
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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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#[clippy::version = "1.31.0"]
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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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declare_clippy_lint! {
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/// ### What it does
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/// Checks for `mem::replace(&mut _, mem::uninitialized())`
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/// and `mem::replace(&mut _, mem::zeroed())`.
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///
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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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/// 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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/// ### Example
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/// ```no_run
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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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#[clippy::version = "1.39.0"]
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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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declare_clippy_lint! {
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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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/// `T` with `T::default()`.
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///
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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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/// take the current value and replace it with the default value of that type.
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///
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/// ### Example
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/// ```no_run
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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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/// ```no_run
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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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#[clippy::version = "1.42.0"]
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pub MEM_REPLACE_WITH_DEFAULT,
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style,
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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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impl_lint_pass!(MemReplace =>
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[MEM_REPLACE_OPTION_WITH_NONE, MEM_REPLACE_WITH_UNINIT, MEM_REPLACE_WITH_DEFAULT]);
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fn check_replace_option_with_none(cx: &LateContext<'_>, dest: &Expr<'_>, expr_span: Span) {
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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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// the replacee's expr after peeling off the `&mut`
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let sugg_expr = peel_ref_operators(cx, dest);
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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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expr_span,
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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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Sugg::hir_with_context(cx, sugg_expr, expr_span.ctxt(), "", &mut applicability).maybe_par()
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),
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applicability,
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);
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}
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fn check_replace_with_uninit(cx: &LateContext<'_>, src: &Expr<'_>, dest: &Expr<'_>, expr_span: Span) {
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if let Some(method_def_id) = cx.typeck_results().type_dependent_def_id(src.hir_id)
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// check if replacement is mem::MaybeUninit::uninit().assume_init()
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&& cx.tcx.is_diagnostic_item(sym::assume_init, method_def_id)
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{
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let Some(top_crate) = std_or_core(cx) else { return };
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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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"{top_crate}::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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if let ExprKind::Call(repl_func, []) = src.kind
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&& let ExprKind::Path(ref repl_func_qpath) = repl_func.kind
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&& let Some(repl_def_id) = cx.qpath_res(repl_func_qpath, repl_func.hir_id).opt_def_id()
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{
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if cx.tcx.is_diagnostic_item(sym::mem_uninitialized, repl_def_id) {
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let Some(top_crate) = std_or_core(cx) else { return };
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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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"{top_crate}::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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&& !cx.typeck_results().expr_ty(src).is_primitive()
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{
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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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}
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}
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}
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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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if is_default_equivalent(cx, src) && !in_external_macro(cx.tcx.sess, expr_span) {
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let Some(top_crate) = std_or_core(cx) else { return };
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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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format!(
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"replacing a value of type `T` with `T::default()` is better expressed using `{top_crate}::mem::take`"
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),
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|diag| {
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if !expr_span.from_expansion() {
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let suggestion = format!("{top_crate}::mem::take({})", snippet(cx, dest.span, ""));
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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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}
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},
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);
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}
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}
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pub struct MemReplace {
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msrv: Msrv,
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}
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impl MemReplace {
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pub fn new(conf: &'static Conf) -> Self {
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Self {
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msrv: conf.msrv.clone(),
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}
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}
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}
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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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if let ExprKind::Call(func, [dest, src]) = expr.kind
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// Check that `expr` is a call to `mem::replace()`
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&& let ExprKind::Path(ref func_qpath) = func.kind
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&& let Some(def_id) = cx.qpath_res(func_qpath, func.hir_id).opt_def_id()
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&& cx.tcx.is_diagnostic_item(sym::mem_replace, def_id)
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{
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// Check that second argument is `Option::None`
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if is_res_lang_ctor(cx, path_res(cx, src), OptionNone) {
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check_replace_option_with_none(cx, dest, expr.span);
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} else if self.msrv.meets(msrvs::MEM_TAKE) && is_expr_used_or_unified(cx.tcx, expr) {
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check_replace_with_default(cx, src, dest, expr.span);
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}
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check_replace_with_uninit(cx, src, dest, expr.span);
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}
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}
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extract_msrv_attr!(LateContext);
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}
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