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merge XOR_SWAP with MANUAL_SWAP
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@HKalbasi
HKalbasi committed Aug 8, 2021
1 parent dbb10b8 commit 6d36d1a
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1 change: 0 additions & 1 deletion CHANGELOG.md
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Expand Up @@ -2900,7 +2900,6 @@ Released 2018-09-13
[`wrong_pub_self_convention`]: https://rust-lang.github.io/rust-clippy/master/index.html#wrong_pub_self_convention
[`wrong_self_convention`]: https://rust-lang.github.io/rust-clippy/master/index.html#wrong_self_convention
[`wrong_transmute`]: https://rust-lang.github.io/rust-clippy/master/index.html#wrong_transmute
[`xor_swap`]: https://rust-lang.github.io/rust-clippy/master/index.html#xor_swap
[`zero_divided_by_zero`]: https://rust-lang.github.io/rust-clippy/master/index.html#zero_divided_by_zero
[`zero_prefixed_literal`]: https://rust-lang.github.io/rust-clippy/master/index.html#zero_prefixed_literal
[`zero_ptr`]: https://rust-lang.github.io/rust-clippy/master/index.html#zero_ptr
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3 changes: 0 additions & 3 deletions clippy_lints/src/lib.rs
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Expand Up @@ -922,7 +922,6 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
suspicious_trait_impl::SUSPICIOUS_OP_ASSIGN_IMPL,
swap::ALMOST_SWAPPED,
swap::MANUAL_SWAP,
swap::XOR_SWAP,
tabs_in_doc_comments::TABS_IN_DOC_COMMENTS,
temporary_assignment::TEMPORARY_ASSIGNMENT,
to_digit_is_some::TO_DIGIT_IS_SOME,
Expand Down Expand Up @@ -1420,7 +1419,6 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
LintId::of(suspicious_trait_impl::SUSPICIOUS_OP_ASSIGN_IMPL),
LintId::of(swap::ALMOST_SWAPPED),
LintId::of(swap::MANUAL_SWAP),
LintId::of(swap::XOR_SWAP),
LintId::of(tabs_in_doc_comments::TABS_IN_DOC_COMMENTS),
LintId::of(temporary_assignment::TEMPORARY_ASSIGNMENT),
LintId::of(to_digit_is_some::TO_DIGIT_IS_SOME),
Expand Down Expand Up @@ -1649,7 +1647,6 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
LintId::of(strings::STRING_FROM_UTF8_AS_BYTES),
LintId::of(strlen_on_c_strings::STRLEN_ON_C_STRINGS),
LintId::of(swap::MANUAL_SWAP),
LintId::of(swap::XOR_SWAP),
LintId::of(temporary_assignment::TEMPORARY_ASSIGNMENT),
LintId::of(transmute::CROSSPOINTER_TRANSMUTE),
LintId::of(transmute::TRANSMUTES_EXPRESSIBLE_AS_PTR_CASTS),
Expand Down
259 changes: 67 additions & 192 deletions clippy_lints/src/swap.rs
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Expand Up @@ -2,15 +2,15 @@ use clippy_utils::diagnostics::{span_lint_and_sugg, span_lint_and_then};
use clippy_utils::source::snippet_with_applicability;
use clippy_utils::sugg::Sugg;
use clippy_utils::ty::is_type_diagnostic_item;
use clippy_utils::{differing_macro_contexts, eq_expr_value};
use clippy_utils::{can_mut_borrow_both, differing_macro_contexts, eq_expr_value};
use if_chain::if_chain;
use rustc_errors::Applicability;
use rustc_hir::{BinOpKind, Block, Expr, ExprKind, PatKind, QPath, Stmt, StmtKind};
use rustc_lint::{LateContext, LateLintPass};
use rustc_middle::ty;
use rustc_session::{declare_lint_pass, declare_tool_lint};
use rustc_span::source_map::Spanned;
use rustc_span::sym;
use rustc_span::{sym, Span};

declare_clippy_lint! {
/// ### What it does
Expand Down Expand Up @@ -65,37 +65,7 @@ declare_clippy_lint! {
"`foo = bar; bar = foo` sequence"
}

declare_clippy_lint! {
/// **What it does:** Checks for uses of xor-based swaps.
///
/// **Why is this bad?** The `std::mem::swap` function exposes the intent better
/// without deinitializing or copying either variable.
///
/// **Known problems:** None.
///
/// **Example:**
///
/// ```rust
/// let mut a = 1;
/// let mut b = 2;
///
/// a ^= b;
/// b ^= a;
/// a ^= b;
/// ```
///
/// Use std::mem::swap() instead:
/// ```rust
/// let mut a = 1;
/// let mut b = 2;
/// std::mem::swap(&mut a, &mut b);
/// ```
pub XOR_SWAP,
complexity,
"xor-based swap of two variables"
}

declare_lint_pass!(Swap => [MANUAL_SWAP, ALMOST_SWAPPED, XOR_SWAP]);
declare_lint_pass!(Swap => [MANUAL_SWAP, ALMOST_SWAPPED]);

impl<'tcx> LateLintPass<'tcx> for Swap {
fn check_block(&mut self, cx: &LateContext<'tcx>, block: &'tcx Block<'_>) {
Expand All @@ -105,6 +75,63 @@ impl<'tcx> LateLintPass<'tcx> for Swap {
}
}

fn generate_swap_warning(cx: &LateContext<'_>, e1: &Expr<'_>, e2: &Expr<'_>, span: Span, is_xor_based: bool) {
let mut applicability = Applicability::MachineApplicable;

if !can_mut_borrow_both(cx, e1, e2) {
if let ExprKind::Index(lhs1, idx1) = e1.kind {
if let ExprKind::Index(lhs2, idx2) = e2.kind {
if eq_expr_value(cx, lhs1, lhs2) {
let ty = cx.typeck_results().expr_ty(lhs1).peel_refs();

if matches!(ty.kind(), ty::Slice(_))
|| matches!(ty.kind(), ty::Array(_, _))
|| is_type_diagnostic_item(cx, ty, sym::vec_type)
|| is_type_diagnostic_item(cx, ty, sym::vecdeque_type)
{
let slice = Sugg::hir_with_applicability(cx, lhs1, "<slice>", &mut applicability);
span_lint_and_sugg(
cx,
MANUAL_SWAP,
span,
&format!("this looks like you are swapping elements of `{}` manually", slice),
"try",
format!(
"{}.swap({}, {})",
slice.maybe_par(),
snippet_with_applicability(cx, idx1.span, "..", &mut applicability),
snippet_with_applicability(cx, idx2.span, "..", &mut applicability),
),
applicability,
);
}
}
}
}
return;
}

let first = Sugg::hir_with_applicability(cx, e1, "..", &mut applicability);
let second = Sugg::hir_with_applicability(cx, e2, "..", &mut applicability);
span_lint_and_then(
cx,
MANUAL_SWAP,
span,
&format!("this looks like you are swapping `{}` and `{}` manually", first, second),
|diag| {
diag.span_suggestion(
span,
"try",
format!("std::mem::swap({}, {})", first.mut_addr(), second.mut_addr()),
applicability,
);
if !is_xor_based {
diag.note("or maybe you should use `std::mem::replace`?");
}
},
);
}

/// Implementation of the `MANUAL_SWAP` lint.
fn check_manual_swap(cx: &LateContext<'_>, block: &Block<'_>) {
for w in block.stmts.windows(3) {
Expand All @@ -128,123 +155,13 @@ fn check_manual_swap(cx: &LateContext<'_>, block: &Block<'_>) {
if eq_expr_value(cx, tmp_init, lhs1);
if eq_expr_value(cx, rhs1, lhs2);
then {
if let ExprKind::Field(lhs1, _) = lhs1.kind {
if let ExprKind::Field(lhs2, _) = lhs2.kind {
if lhs1.hir_id.owner == lhs2.hir_id.owner {
return;
}
}
}

let mut applicability = Applicability::MachineApplicable;

let slice = check_for_slice(cx, lhs1, lhs2);
let (replace, what, sugg) = if let Slice::NotSwappable = slice {
return;
} else if let Slice::Swappable(slice, idx1, idx2) = slice {
if let Some(slice) = Sugg::hir_opt(cx, slice) {
(
false,
format!(" elements of `{}`", slice),
format!(
"{}.swap({}, {})",
slice.maybe_par(),
snippet_with_applicability(cx, idx1.span, "..", &mut applicability),
snippet_with_applicability(cx, idx2.span, "..", &mut applicability),
),
)
} else {
(false, String::new(), String::new())
}
} else if let (Some(first), Some(second)) = (Sugg::hir_opt(cx, lhs1), Sugg::hir_opt(cx, rhs1)) {
(
true,
format!(" `{}` and `{}`", first, second),
format!("std::mem::swap({}, {})", first.mut_addr(), second.mut_addr()),
)
} else {
(true, String::new(), String::new())
};

let span = w[0].span.to(second.span);

span_lint_and_then(
cx,
MANUAL_SWAP,
span,
&format!("this looks like you are swapping{} manually", what),
|diag| {
if !sugg.is_empty() {
diag.span_suggestion(
span,
"try",
sugg,
applicability,
);

if replace {
diag.note("or maybe you should use `std::mem::replace`?");
}
}
}
);
generate_swap_warning(cx, lhs1, lhs2, span, false);
}
}
}
}

enum Slice<'a> {
/// `slice.swap(idx1, idx2)` can be used
///
/// ## Example
///
/// ```rust
/// # let mut a = vec![0, 1];
/// let t = a[1];
/// a[1] = a[0];
/// a[0] = t;
/// // can be written as
/// a.swap(0, 1);
/// ```
Swappable(&'a Expr<'a>, &'a Expr<'a>, &'a Expr<'a>),
/// The `swap` function cannot be used.
///
/// ## Example
///
/// ```rust
/// # let mut a = [vec![1, 2], vec![3, 4]];
/// let t = a[0][1];
/// a[0][1] = a[1][0];
/// a[1][0] = t;
/// ```
NotSwappable,
/// Not a slice
None,
}

/// Checks if both expressions are index operations into "slice-like" types.
fn check_for_slice<'a>(cx: &LateContext<'_>, lhs1: &'a Expr<'_>, lhs2: &'a Expr<'_>) -> Slice<'a> {
if let ExprKind::Index(lhs1, idx1) = lhs1.kind {
if let ExprKind::Index(lhs2, idx2) = lhs2.kind {
if eq_expr_value(cx, lhs1, lhs2) {
let ty = cx.typeck_results().expr_ty(lhs1).peel_refs();

if matches!(ty.kind(), ty::Slice(_))
|| matches!(ty.kind(), ty::Array(_, _))
|| is_type_diagnostic_item(cx, ty, sym::vec_type)
|| is_type_diagnostic_item(cx, ty, sym::vecdeque_type)
{
return Slice::Swappable(lhs1, idx1, idx2);
}
} else {
return Slice::NotSwappable;
}
}
}

Slice::None
}

/// Implementation of the `ALMOST_SWAPPED` lint.
fn check_suspicious_swap(cx: &LateContext<'_>, block: &Block<'_>) {
for w in block.stmts.windows(2) {
Expand Down Expand Up @@ -295,62 +212,20 @@ fn check_suspicious_swap(cx: &LateContext<'_>, block: &Block<'_>) {
}
}

/// Implementation of the `XOR_SWAP` lint.
/// Implementation of the xor case for `MANUAL_SWAP` lint.
fn check_xor_swap(cx: &LateContext<'_>, block: &Block<'_>) {
for window in block.stmts.windows(3) {
if_chain! {
if let Some((lhs0, rhs0)) = extract_sides_of_xor_assign(&window[0]);
if let Some((lhs1, rhs1)) = extract_sides_of_xor_assign(&window[1]);
if let Some((lhs2, rhs2)) = extract_sides_of_xor_assign(&window[2]);
if eq_expr_value(cx, lhs0, rhs1)
&& eq_expr_value(cx, rhs1, lhs2)
&& eq_expr_value(cx, rhs0, lhs1)
&& eq_expr_value(cx, lhs1, rhs2);
if eq_expr_value(cx, lhs0, rhs1);
if eq_expr_value(cx, lhs2, rhs1);
if eq_expr_value(cx, lhs1, rhs0);
if eq_expr_value(cx, lhs1, rhs2);
then {
let span = window[0].span.to(window[2].span);
let mut applicability = Applicability::MachineApplicable;
match check_for_slice(cx, lhs0, rhs0) {
Slice::Swappable(slice, idx0, idx1) => {
if let Some(slice) = Sugg::hir_opt(cx, slice) {
span_lint_and_sugg(
cx,
XOR_SWAP,
span,
&format!(
"this xor-based swap of the elements of `{}` can be \
more clearly expressed using `.swap`",
slice
),
"try",
format!(
"{}.swap({}, {})",
slice.maybe_par(),
snippet_with_applicability(cx, idx0.span, "..", &mut applicability),
snippet_with_applicability(cx, idx1.span, "..", &mut applicability)
),
applicability
)
}
}
Slice::None => {
if let (Some(first), Some(second)) = (Sugg::hir_opt(cx, lhs0), Sugg::hir_opt(cx, rhs0)) {
span_lint_and_sugg(
cx,
XOR_SWAP,
span,
&format!(
"this xor-based swap of `{}` and `{}` can be \
more clearly expressed using `std::mem::swap`",
first, second
),
"try",
format!("std::mem::swap({}, {})", first.mut_addr(), second.mut_addr()),
applicability,
);
}
}
Slice::NotSwappable => {}
}
generate_swap_warning(cx, lhs0, rhs0, span, true);
}
};
}
Expand Down

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