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Fix FP in manual_swap lint with slice-like types

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This commit is contained in:
flip1995 2019-12-03 13:20:42 +01:00
parent d3232b0fce
commit d1d5f790f5
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GPG Key ID: 693086869D506637
1 changed files with 55 additions and 24 deletions
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79
clippy_lints/src/swap.rs
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@ -97,29 +97,6 @@ fn check_manual_swap(cx: &LateContext<'_, '_>, block: &Block) {
if SpanlessEq::new(cx).ignore_fn().eq_expr(tmp_init, lhs1);
if SpanlessEq::new(cx).ignore_fn().eq_expr(rhs1, lhs2);
then {
fn check_for_slice<'a>(
cx: &LateContext<'_, '_>,
lhs1: &'a Expr,
lhs2: &'a Expr,
) -> Option<(&'a Expr, &'a Expr, &'a Expr)> {
if let ExprKind::Index(ref lhs1, ref idx1) = lhs1.kind {
if let ExprKind::Index(ref lhs2, ref idx2) = lhs2.kind {
if SpanlessEq::new(cx).ignore_fn().eq_expr(lhs1, lhs2) {
let ty = walk_ptrs_ty(cx.tables.expr_ty(lhs1));
if matches!(ty.kind, ty::Slice(_)) ||
matches!(ty.kind, ty::Array(_, _)) ||
is_type_diagnostic_item(cx, ty, Symbol::intern("vec_type")) ||
match_type(cx, ty, &paths::VEC_DEQUE) {
return Some((lhs1, idx1, idx2));
}
}
}
}
None
}
if let ExprKind::Field(ref lhs1, _) = lhs1.kind {
if let ExprKind::Field(ref lhs2, _) = lhs2.kind {
if lhs1.hir_id.owner_def_id() == lhs2.hir_id.owner_def_id() {
@ -128,7 +105,11 @@ fn check_manual_swap(cx: &LateContext<'_, '_>, block: &Block) {
}
}
let (replace, what, sugg) = if let Some((slice, idx1, idx2)) = check_for_slice(cx, lhs1, lhs2) {
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),
@ -171,6 +152,56 @@ fn check_manual_swap(cx: &LateContext<'_, '_>, block: &Block) {
}
}
enum Slice<'a> {
/// `slice.swap(idx1, idx2)` can be used
///
/// ## Example
///
/// ```rust
/// let t = a[1];
/// a[1] = a[0];
/// a[0] = t;
/// // can be written as
/// a.swap(0, 1);
/// ```
Swappable(&'a Expr, &'a Expr, &'a Expr),
/// The `swap` function cannot be used.
///
/// ## Example
///
/// ```rust
/// 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(ref lhs1, ref idx1) = lhs1.kind {
if let ExprKind::Index(ref lhs2, ref idx2) = lhs2.kind {
if SpanlessEq::new(cx).ignore_fn().eq_expr(lhs1, lhs2) {
let ty = walk_ptrs_ty(cx.tables.expr_ty(lhs1));
if matches!(ty.kind, ty::Slice(_))
|| matches!(ty.kind, ty::Array(_, _))
|| is_type_diagnostic_item(cx, ty, Symbol::intern("vec_type"))
|| match_type(cx, ty, &paths::VEC_DEQUE)
{
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) {