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Auto merge of #5727 - rail-rain:manual_memcpy_with_counter, r=flip1995

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Expands `manual_memcpy` to lint ones with loop counters

Closes #1670

This PR expands `manual_memcpy` to lint ones with loop counters as described in https://github.com/rust-lang/rust-clippy/issues/1670#issuecomment-293280204

Although the current code is working, I have a couple of questions and concerns.

~~Firstly, I manually implemented `Clone` for `Sugg` because `AssocOp` lacks `Clone`. As `AssocOp` only holds an enum, which is `Copy`, as a value, it seems `AssocOp` can be `Clone`; but, I was not sure where to ask it. Should I make a PR to `rustc`?~~ The [PR]( https://github.com/rust-lang/rust/pull/73629) was made.

Secondly, manual copying with loop counters are likely to trigger `needless_range_loop` and `explicit_counter_loop` along with `manual_memcpy`; in fact, I explicitly allowed them in the tests. Is there any way to disable these two lints when a code triggers `manual_memcpy`?

And, another thing I'd like to note is that `Sugg` adds unnecessary parentheses when expressions with parentheses passed to its `hir` function, as seen here:

```
error: it looks like you're manually copying between slices
  --> $DIR/manual_memcpy.rs:145:14
   |
LL |     for i in 3..(3 + src.len()) {
   |              ^^^^^^^^^^^^^^^^^^ help: try replacing the loop by: `dst[3..((3 + src.len()))].clone_from_slice(&src[..((3 + src.len()) - 3)])
```

However, using the `hir` function is needed to prevent the suggestion causing  errors when users use bitwise operations; and also this have already existed, for example: `verbose_bit_mask`. Thus, I think this is fine.

changelog: Expands `manual_memcpy` to lint ones with loop counters
This commit is contained in:
bors 2020-10-10 06:32:32 +00:00
commit dbc02854fc
8 changed files with 807 additions and 300 deletions
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644
clippy_lints/src/loops.rs
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@ -5,9 +5,8 @@ use crate::utils::usage::{is_unused, mutated_variables};
use crate::utils::{
contains_name, get_enclosing_block, get_parent_expr, get_trait_def_id, has_iter_method, higher, implements_trait,
is_integer_const, is_no_std_crate, is_refutable, is_type_diagnostic_item, last_path_segment, match_trait_method,
match_type, match_var, multispan_sugg, qpath_res, snippet, snippet_opt, snippet_with_applicability,
snippet_with_macro_callsite, span_lint, span_lint_and_help, span_lint_and_sugg, span_lint_and_then, sugg,
SpanlessEq,
match_type, match_var, multispan_sugg, qpath_res, snippet, snippet_with_applicability, snippet_with_macro_callsite,
span_lint, span_lint_and_help, span_lint_and_sugg, span_lint_and_then, sugg, SpanlessEq,
};
use if_chain::if_chain;
use rustc_ast::ast;
@ -769,15 +768,28 @@ fn check_for_loop<'tcx>(
body: &'tcx Expr<'_>,
expr: &'tcx Expr<'_>,
) {
check_for_loop_range(cx, pat, arg, body, expr);
let is_manual_memcpy_triggered = detect_manual_memcpy(cx, pat, arg, body, expr);
if !is_manual_memcpy_triggered {
check_for_loop_range(cx, pat, arg, body, expr);
check_for_loop_explicit_counter(cx, pat, arg, body, expr);
}
check_for_loop_arg(cx, pat, arg, expr);
check_for_loop_explicit_counter(cx, pat, arg, body, expr);
check_for_loop_over_map_kv(cx, pat, arg, body, expr);
check_for_mut_range_bound(cx, arg, body);
detect_manual_memcpy(cx, pat, arg, body, expr);
detect_same_item_push(cx, pat, arg, body, expr);
}
// this function assumes the given expression is a `for` loop.
fn get_span_of_entire_for_loop(expr: &Expr<'_>) -> Span {
// for some reason this is the only way to get the `Span`
// of the entire `for` loop
if let ExprKind::Match(_, arms, _) = &expr.kind {
arms[0].body.span
} else {
unreachable!()
}
}
fn same_var<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'_>, var: HirId) -> bool {
if_chain! {
if let ExprKind::Path(qpath) = &expr.kind;
@ -793,36 +805,131 @@ fn same_var<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'_>, var: HirId) -> bool {
}
}
/// a wrapper of `Sugg`. Besides what `Sugg` do, this removes unnecessary `0`;
/// and also, it avoids subtracting a variable from the same one by replacing it with `0`.
/// it exists for the convenience of the overloaded operators while normal functions can do the
/// same.
#[derive(Clone)]
struct MinifyingSugg<'a>(Sugg<'a>);
impl<'a> MinifyingSugg<'a> {
fn as_str(&self) -> &str {
let Sugg::NonParen(s) | Sugg::MaybeParen(s) | Sugg::BinOp(_, s) = &self.0;
s.as_ref()
}
fn into_sugg(self) -> Sugg<'a> {
self.0
}
}
impl<'a> From<Sugg<'a>> for MinifyingSugg<'a> {
fn from(sugg: Sugg<'a>) -> Self {
Self(sugg)
}
}
impl std::ops::Add for &MinifyingSugg<'static> {
type Output = MinifyingSugg<'static>;
fn add(self, rhs: &MinifyingSugg<'static>) -> MinifyingSugg<'static> {
match (self.as_str(), rhs.as_str()) {
("0", _) => rhs.clone(),
(_, "0") => self.clone(),
(_, _) => (&self.0 + &rhs.0).into(),
}
}
}
impl std::ops::Sub for &MinifyingSugg<'static> {
type Output = MinifyingSugg<'static>;
fn sub(self, rhs: &MinifyingSugg<'static>) -> MinifyingSugg<'static> {
match (self.as_str(), rhs.as_str()) {
(_, "0") => self.clone(),
("0", _) => (-rhs.0.clone()).into(),
(x, y) if x == y => sugg::ZERO.into(),
(_, _) => (&self.0 - &rhs.0).into(),
}
}
}
impl std::ops::Add<&MinifyingSugg<'static>> for MinifyingSugg<'static> {
type Output = MinifyingSugg<'static>;
fn add(self, rhs: &MinifyingSugg<'static>) -> MinifyingSugg<'static> {
match (self.as_str(), rhs.as_str()) {
("0", _) => rhs.clone(),
(_, "0") => self,
(_, _) => (self.0 + &rhs.0).into(),
}
}
}
impl std::ops::Sub<&MinifyingSugg<'static>> for MinifyingSugg<'static> {
type Output = MinifyingSugg<'static>;
fn sub(self, rhs: &MinifyingSugg<'static>) -> MinifyingSugg<'static> {
match (self.as_str(), rhs.as_str()) {
(_, "0") => self,
("0", _) => (-rhs.0.clone()).into(),
(x, y) if x == y => sugg::ZERO.into(),
(_, _) => (self.0 - &rhs.0).into(),
}
}
}
/// a wrapper around `MinifyingSugg`, which carries a operator like currying
/// so that the suggested code become more efficient (e.g. `foo + -bar` `foo - bar`).
struct Offset {
value: MinifyingSugg<'static>,
sign: OffsetSign,
}
#[derive(Clone, Copy)]
enum OffsetSign {
Positive,
Negative,
}
struct Offset {
value: String,
sign: OffsetSign,
}
impl Offset {
fn negative(value: String) -> Self {
fn negative(value: Sugg<'static>) -> Self {
Self {
value,
value: value.into(),
sign: OffsetSign::Negative,
}
}
fn positive(value: String) -> Self {
fn positive(value: Sugg<'static>) -> Self {
Self {
value,
value: value.into(),
sign: OffsetSign::Positive,
}
}
fn empty() -> Self {
Self::positive(sugg::ZERO)
}
}
struct FixedOffsetVar<'hir> {
var: &'hir Expr<'hir>,
offset: Offset,
fn apply_offset(lhs: &MinifyingSugg<'static>, rhs: &Offset) -> MinifyingSugg<'static> {
match rhs.sign {
OffsetSign::Positive => lhs + &rhs.value,
OffsetSign::Negative => lhs - &rhs.value,
}
}
#[derive(Debug, Clone, Copy)]
enum StartKind<'hir> {
Range,
Counter { initializer: &'hir Expr<'hir> },
}
struct IndexExpr<'hir> {
base: &'hir Expr<'hir>,
idx: StartKind<'hir>,
idx_offset: Offset,
}
struct Start<'hir> {
id: HirId,
kind: StartKind<'hir>,
}
fn is_slice_like<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'_>) -> bool {
@ -845,14 +952,28 @@ fn fetch_cloned_expr<'tcx>(expr: &'tcx Expr<'tcx>) -> &'tcx Expr<'tcx> {
}
}
fn get_offset<'tcx>(cx: &LateContext<'tcx>, idx: &Expr<'_>, var: HirId) -> Option<Offset> {
fn extract_offset<'tcx>(cx: &LateContext<'tcx>, e: &Expr<'_>, var: HirId) -> Option<String> {
fn get_details_from_idx<'tcx>(
cx: &LateContext<'tcx>,
idx: &Expr<'_>,
starts: &[Start<'tcx>],
) -> Option<(StartKind<'tcx>, Offset)> {
fn get_start<'tcx>(cx: &LateContext<'tcx>, e: &Expr<'_>, starts: &[Start<'tcx>]) -> Option<StartKind<'tcx>> {
starts.iter().find_map(|start| {
if same_var(cx, e, start.id) {
Some(start.kind)
} else {
None
}
})
}
fn get_offset<'tcx>(cx: &LateContext<'tcx>, e: &Expr<'_>, starts: &[Start<'tcx>]) -> Option<Sugg<'static>> {
match &e.kind {
ExprKind::Lit(l) => match l.node {
ast::LitKind::Int(x, _ty) => Some(x.to_string()),
ast::LitKind::Int(x, _ty) => Some(Sugg::NonParen(x.to_string().into())),
_ => None,
},
ExprKind::Path(..) if !same_var(cx, e, var) => Some(snippet_opt(cx, e.span).unwrap_or_else(|| "??".into())),
ExprKind::Path(..) if get_start(cx, e, starts).is_none() => Some(Sugg::hir(cx, e, "???")),
_ => None,
}
}
@ -860,55 +981,89 @@ fn get_offset<'tcx>(cx: &LateContext<'tcx>, idx: &Expr<'_>, var: HirId) -> Optio
match idx.kind {
ExprKind::Binary(op, lhs, rhs) => match op.node {
BinOpKind::Add => {
let offset_opt = if same_var(cx, lhs, var) {
extract_offset(cx, rhs, var)
} else if same_var(cx, rhs, var) {
extract_offset(cx, lhs, var)
} else {
None
};
let offset_opt = get_start(cx, lhs, starts)
.and_then(|s| get_offset(cx, rhs, starts).map(|o| (s, o)))
.or_else(|| get_start(cx, rhs, starts).and_then(|s| get_offset(cx, lhs, starts).map(|o| (s, o))));
offset_opt.map(Offset::positive)
offset_opt.map(|(s, o)| (s, Offset::positive(o)))
},
BinOpKind::Sub => {
get_start(cx, lhs, starts).and_then(|s| get_offset(cx, rhs, starts).map(|o| (s, Offset::negative(o))))
},
BinOpKind::Sub if same_var(cx, lhs, var) => extract_offset(cx, rhs, var).map(Offset::negative),
_ => None,
},
ExprKind::Path(..) if same_var(cx, idx, var) => Some(Offset::positive("0".into())),
ExprKind::Path(..) => get_start(cx, idx, starts).map(|s| (s, Offset::empty())),
_ => None,
}
}
fn get_assignments<'tcx>(body: &'tcx Expr<'tcx>) -> impl Iterator<Item = Option<(&'tcx Expr<'tcx>, &'tcx Expr<'tcx>)>> {
fn get_assignment<'tcx>(e: &'tcx Expr<'tcx>) -> Option<(&'tcx Expr<'tcx>, &'tcx Expr<'tcx>)> {
if let ExprKind::Assign(lhs, rhs, _) = e.kind {
Some((lhs, rhs))
} else {
None
}
}
// This is one of few ways to return different iterators
// derived from: https://stackoverflow.com/questions/29760668/conditionally-iterate-over-one-of-several-possible-iterators/52064434#52064434
let mut iter_a = None;
let mut iter_b = None;
if let ExprKind::Block(b, _) = body.kind {
let Block { stmts, expr, .. } = *b;
iter_a = stmts
.iter()
.filter_map(|stmt| match stmt.kind {
StmtKind::Local(..) | StmtKind::Item(..) => None,
StmtKind::Expr(e) | StmtKind::Semi(e) => Some(e),
})
.chain(expr.into_iter())
.map(get_assignment)
.into()
fn get_assignment<'tcx>(e: &'tcx Expr<'tcx>) -> Option<(&'tcx Expr<'tcx>, &'tcx Expr<'tcx>)> {
if let ExprKind::Assign(lhs, rhs, _) = e.kind {
Some((lhs, rhs))
} else {
iter_b = Some(get_assignment(body))
None
}
}
iter_a.into_iter().flatten().chain(iter_b.into_iter())
/// Get assignments from the given block.
/// The returned iterator yields `None` if no assignment expressions are there,
/// filtering out the increments of the given whitelisted loop counters;
/// because its job is to make sure there's nothing other than assignments and the increments.
fn get_assignments<'a: 'c, 'tcx: 'c, 'c>(
cx: &'a LateContext<'tcx>,
Block { stmts, expr, .. }: &'tcx Block<'tcx>,
loop_counters: &'c [Start<'tcx>],
) -> impl Iterator<Item = Option<(&'tcx Expr<'tcx>, &'tcx Expr<'tcx>)>> + 'c {
// As the `filter` and `map` below do different things, I think putting together
// just increases complexity. (cc #3188 and #4193)
#[allow(clippy::filter_map)]
stmts
.iter()
.filter_map(move |stmt| match stmt.kind {
StmtKind::Local(..) | StmtKind::Item(..) => None,
StmtKind::Expr(e) | StmtKind::Semi(e) => Some(e),
})
.chain((*expr).into_iter())
.filter(move |e| {
if let ExprKind::AssignOp(_, place, _) = e.kind {
!loop_counters
.iter()
// skip the first item which should be `StartKind::Range`
// this makes it possible to use the slice with `StartKind::Range` in the same iterator loop.
.skip(1)
.any(|counter| same_var(cx, place, counter.id))
} else {
true
}
})
.map(get_assignment)
}
fn get_loop_counters<'a, 'tcx>(
cx: &'a LateContext<'tcx>,
body: &'tcx Block<'tcx>,
expr: &'tcx Expr<'_>,
) -> Option<impl Iterator<Item = Start<'tcx>> + 'a> {
// Look for variables that are incremented once per loop iteration.
let mut increment_visitor = IncrementVisitor::new(cx);
walk_block(&mut increment_visitor, body);
// For each candidate, check the parent block to see if
// it's initialized to zero at the start of the loop.
get_enclosing_block(&cx, expr.hir_id).and_then(|block| {
increment_visitor
.into_results()
.filter_map(move |var_id| {
let mut initialize_visitor = InitializeVisitor::new(cx, expr, var_id);
walk_block(&mut initialize_visitor, block);
initialize_visitor.get_result().map(|(_, initializer)| Start {
id: var_id,
kind: StartKind::Counter { initializer },
})
})
.into()
})
}
fn build_manual_memcpy_suggestion<'tcx>(
@ -916,80 +1071,97 @@ fn build_manual_memcpy_suggestion<'tcx>(
start: &Expr<'_>,
end: &Expr<'_>,
limits: ast::RangeLimits,
dst_var: FixedOffsetVar<'_>,
src_var: FixedOffsetVar<'_>,
dst: &IndexExpr<'_>,
src: &IndexExpr<'_>,
) -> String {
fn print_sum(arg1: &str, arg2: &Offset) -> String {
match (arg1, &arg2.value[..], arg2.sign) {
("0", "0", _) => "0".into(),
("0", x, OffsetSign::Positive) | (x, "0", _) => x.into(),
("0", x, OffsetSign::Negative) => format!("-{}", x),
(x, y, OffsetSign::Positive) => format!("({} + {})", x, y),
(x, y, OffsetSign::Negative) => {
if x == y {
"0".into()
} else {
format!("({} - {})", x, y)
}
},
}
}
fn print_offset(start_str: &str, inline_offset: &Offset) -> String {
let offset = print_sum(start_str, inline_offset);
fn print_offset(offset: MinifyingSugg<'static>) -> MinifyingSugg<'static> {
if offset.as_str() == "0" {
"".into()
sugg::EMPTY.into()
} else {
offset
}
}
let print_limit = |end: &Expr<'_>, offset: Offset, var: &Expr<'_>| {
let print_limit = |end: &Expr<'_>, end_str: &str, base: &Expr<'_>, sugg: MinifyingSugg<'static>| {
if_chain! {
if let ExprKind::MethodCall(method, _, len_args, _) = end.kind;
if method.ident.name == sym!(len);
if len_args.len() == 1;
if let Some(arg) = len_args.get(0);
if var_def_id(cx, arg) == var_def_id(cx, var);
if var_def_id(cx, arg) == var_def_id(cx, base);
then {
match offset.sign {
OffsetSign::Negative => format!("({} - {})", snippet(cx, end.span, "<src>.len()"), offset.value),
OffsetSign::Positive => "".into(),
if sugg.as_str() == end_str {
sugg::EMPTY.into()
} else {
sugg
}
} else {
let end_str = match limits {
match limits {
ast::RangeLimits::Closed => {
let end = sugg::Sugg::hir(cx, end, "<count>");
format!("{}", end + sugg::ONE)
sugg + &sugg::ONE.into()
},
ast::RangeLimits::HalfOpen => format!("{}", snippet(cx, end.span, "..")),
};
print_sum(&end_str, &offset)
ast::RangeLimits::HalfOpen => sugg,
}
}
}
};
let start_str = snippet(cx, start.span, "").to_string();
let dst_offset = print_offset(&start_str, &dst_var.offset);
let dst_limit = print_limit(end, dst_var.offset, dst_var.var);
let src_offset = print_offset(&start_str, &src_var.offset);
let src_limit = print_limit(end, src_var.offset, src_var.var);
let start_str = Sugg::hir(cx, start, "").into();
let end_str: MinifyingSugg<'_> = Sugg::hir(cx, end, "").into();
let dst_var_name = snippet_opt(cx, dst_var.var.span).unwrap_or_else(|| "???".into());
let src_var_name = snippet_opt(cx, src_var.var.span).unwrap_or_else(|| "???".into());
let print_offset_and_limit = |idx_expr: &IndexExpr<'_>| match idx_expr.idx {
StartKind::Range => (
print_offset(apply_offset(&start_str, &idx_expr.idx_offset)).into_sugg(),
print_limit(
end,
end_str.as_str(),
idx_expr.base,
apply_offset(&end_str, &idx_expr.idx_offset),
)
.into_sugg(),
),
StartKind::Counter { initializer } => {
let counter_start = Sugg::hir(cx, initializer, "").into();
(
print_offset(apply_offset(&counter_start, &idx_expr.idx_offset)).into_sugg(),
print_limit(
end,
end_str.as_str(),
idx_expr.base,
apply_offset(&end_str, &idx_expr.idx_offset) + &counter_start - &start_str,
)
.into_sugg(),
)
},
};
let dst = if dst_offset == "" && dst_limit == "" {
dst_var_name
let (dst_offset, dst_limit) = print_offset_and_limit(&dst);
let (src_offset, src_limit) = print_offset_and_limit(&src);
let dst_base_str = snippet(cx, dst.base.span, "???");
let src_base_str = snippet(cx, src.base.span, "???");
let dst = if dst_offset == sugg::EMPTY && dst_limit == sugg::EMPTY {
dst_base_str
} else {
format!("{}[{}..{}]", dst_var_name, dst_offset, dst_limit)
format!(
"{}[{}..{}]",
dst_base_str,
dst_offset.maybe_par(),
dst_limit.maybe_par()
)
.into()
};
format!(
"{}.clone_from_slice(&{}[{}..{}])",
dst, src_var_name, src_offset, src_limit
"{}.clone_from_slice(&{}[{}..{}]);",
dst,
src_base_str,
src_offset.maybe_par(),
src_limit.maybe_par()
)
}
/// Checks for for loops that sequentially copy items from one slice-like
/// object to another.
fn detect_manual_memcpy<'tcx>(
@ -998,7 +1170,7 @@ fn detect_manual_memcpy<'tcx>(
arg: &'tcx Expr<'_>,
body: &'tcx Expr<'_>,
expr: &'tcx Expr<'_>,
) {
) -> bool {
if let Some(higher::Range {
start: Some(start),
end: Some(end),
@ -1007,32 +1179,53 @@ fn detect_manual_memcpy<'tcx>(
{
// the var must be a single name
if let PatKind::Binding(_, canonical_id, _, _) = pat.kind {
// The only statements in the for loops can be indexed assignments from
// indexed retrievals.
let big_sugg = get_assignments(body)
let mut starts = vec![Start {
id: canonical_id,
kind: StartKind::Range,
}];
// This is one of few ways to return different iterators
// derived from: https://stackoverflow.com/questions/29760668/conditionally-iterate-over-one-of-several-possible-iterators/52064434#52064434
let mut iter_a = None;
let mut iter_b = None;
if let ExprKind::Block(block, _) = body.kind {
if let Some(loop_counters) = get_loop_counters(cx, block, expr) {
starts.extend(loop_counters);
}
iter_a = Some(get_assignments(cx, block, &starts));
} else {
iter_b = Some(get_assignment(body));
}
let assignments = iter_a.into_iter().flatten().chain(iter_b.into_iter());
let big_sugg = assignments
// The only statements in the for loops can be indexed assignments from
// indexed retrievals (except increments of loop counters).
.map(|o| {
o.and_then(|(lhs, rhs)| {
let rhs = fetch_cloned_expr(rhs);
if_chain! {
if let ExprKind::Index(seqexpr_left, idx_left) = lhs.kind;
if let ExprKind::Index(seqexpr_right, idx_right) = rhs.kind;
if is_slice_like(cx, cx.typeck_results().expr_ty(seqexpr_left))
&& is_slice_like(cx, cx.typeck_results().expr_ty(seqexpr_right));
if let Some(offset_left) = get_offset(cx, &idx_left, canonical_id);
if let Some(offset_right) = get_offset(cx, &idx_right, canonical_id);
if let ExprKind::Index(base_left, idx_left) = lhs.kind;
if let ExprKind::Index(base_right, idx_right) = rhs.kind;
if is_slice_like(cx, cx.typeck_results().expr_ty(base_left))
&& is_slice_like(cx, cx.typeck_results().expr_ty(base_right));
if let Some((start_left, offset_left)) = get_details_from_idx(cx, &idx_left, &starts);
if let Some((start_right, offset_right)) = get_details_from_idx(cx, &idx_right, &starts);
// Source and destination must be different
if var_def_id(cx, seqexpr_left) != var_def_id(cx, seqexpr_right);
if var_def_id(cx, base_left) != var_def_id(cx, base_right);
then {
Some((FixedOffsetVar { var: seqexpr_left, offset: offset_left },
FixedOffsetVar { var: seqexpr_right, offset: offset_right }))
Some((IndexExpr { base: base_left, idx: start_left, idx_offset: offset_left },
IndexExpr { base: base_right, idx: start_right, idx_offset: offset_right }))
} else {
None
}
}
})
})
.map(|o| o.map(|(dst, src)| build_manual_memcpy_suggestion(cx, start, end, limits, dst, src)))
.map(|o| o.map(|(dst, src)| build_manual_memcpy_suggestion(cx, start, end, limits, &dst, &src)))
.collect::<Option<Vec<_>>>()
.filter(|v| !v.is_empty())
.map(|v| v.join("\n "));
@ -1041,15 +1234,17 @@ fn detect_manual_memcpy<'tcx>(
span_lint_and_sugg(
cx,
MANUAL_MEMCPY,
expr.span,
get_span_of_entire_for_loop(expr),
"it looks like you're manually copying between slices",
"try replacing the loop by",
big_sugg,
Applicability::Unspecified,
);
return true;
}
}
}
false
}
// Scans the body of the for loop and determines whether lint should be given
@ -1532,6 +1727,9 @@ fn check_arg_type(cx: &LateContext<'_>, pat: &Pat<'_>, arg: &Expr<'_>) {
}
}
// To trigger the EXPLICIT_COUNTER_LOOP lint, a variable must be
// incremented exactly once in the loop body, and initialized to zero
// at the start of the loop.
fn check_for_loop_explicit_counter<'tcx>(
cx: &LateContext<'tcx>,
pat: &'tcx Pat<'_>,
@ -1540,40 +1738,23 @@ fn check_for_loop_explicit_counter<'tcx>(
expr: &'tcx Expr<'_>,
) {
// Look for variables that are incremented once per loop iteration.
let mut visitor = IncrementVisitor {
cx,
states: FxHashMap::default(),
depth: 0,
done: false,
};
walk_expr(&mut visitor, body);
let mut increment_visitor = IncrementVisitor::new(cx);
walk_expr(&mut increment_visitor, body);
// For each candidate, check the parent block to see if
// it's initialized to zero at the start of the loop.
if let Some(block) = get_enclosing_block(&cx, expr.hir_id) {
for (id, _) in visitor.states.iter().filter(|&(_, v)| *v == VarState::IncrOnce) {
let mut visitor2 = InitializeVisitor {
cx,
end_expr: expr,
var_id: *id,
state: VarState::IncrOnce,
name: None,
depth: 0,
past_loop: false,
};
walk_block(&mut visitor2, block);
for id in increment_visitor.into_results() {
let mut initialize_visitor = InitializeVisitor::new(cx, expr, id);
walk_block(&mut initialize_visitor, block);
if visitor2.state == VarState::Warn {
if let Some(name) = visitor2.name {
if_chain! {
if let Some((name, initializer)) = initialize_visitor.get_result();
if is_integer_const(cx, initializer, 0);
then {
let mut applicability = Applicability::MachineApplicable;
// for some reason this is the only way to get the `Span`
// of the entire `for` loop
let for_span = if let ExprKind::Match(_, arms, _) = &expr.kind {
arms[0].body.span
} else {
unreachable!()
};
let for_span = get_span_of_entire_for_loop(expr);
span_lint_and_sugg(
cx,
@ -2126,26 +2307,42 @@ fn is_simple_break_expr(expr: &Expr<'_>) -> bool {
}
}
// To trigger the EXPLICIT_COUNTER_LOOP lint, a variable must be
// incremented exactly once in the loop body, and initialized to zero
// at the start of the loop.
#[derive(Debug, PartialEq)]
enum VarState {
enum IncrementVisitorVarState {
Initial, // Not examined yet
IncrOnce, // Incremented exactly once, may be a loop counter
Declared, // Declared but not (yet) initialized to zero
Warn,
DontWarn,
}
/// Scan a for loop for variables that are incremented exactly once and not used after that.
struct IncrementVisitor<'a, 'tcx> {
cx: &'a LateContext<'tcx>, // context reference
states: FxHashMap<HirId, VarState>, // incremented variables
depth: u32, // depth of conditional expressions
cx: &'a LateContext<'tcx>, // context reference
states: FxHashMap<HirId, IncrementVisitorVarState>, // incremented variables
depth: u32, // depth of conditional expressions
done: bool,
}
impl<'a, 'tcx> IncrementVisitor<'a, 'tcx> {
fn new(cx: &'a LateContext<'tcx>) -> Self {
Self {
cx,
states: FxHashMap::default(),
depth: 0,
done: false,
}
}
fn into_results(self) -> impl Iterator<Item = HirId> {
self.states.into_iter().filter_map(|(id, state)| {
if state == IncrementVisitorVarState::IncrOnce {
Some(id)
} else {
None
}
})
}
}
impl<'a, 'tcx> Visitor<'tcx> for IncrementVisitor<'a, 'tcx> {
type Map = Map<'tcx>;
@ -2157,85 +2354,118 @@ impl<'a, 'tcx> Visitor<'tcx> for IncrementVisitor<'a, 'tcx> {
// If node is a variable
if let Some(def_id) = var_def_id(self.cx, expr) {
if let Some(parent) = get_parent_expr(self.cx, expr) {
let state = self.states.entry(def_id).or_insert(VarState::Initial);
if *state == VarState::IncrOnce {
*state = VarState::DontWarn;
let state = self.states.entry(def_id).or_insert(IncrementVisitorVarState::Initial);
if *state == IncrementVisitorVarState::IncrOnce {
*state = IncrementVisitorVarState::DontWarn;
return;
}
match parent.kind {
ExprKind::AssignOp(op, ref lhs, ref rhs) => {
if lhs.hir_id == expr.hir_id {
if op.node == BinOpKind::Add && is_integer_const(self.cx, rhs, 1) {
*state = match *state {
VarState::Initial if self.depth == 0 => VarState::IncrOnce,
_ => VarState::DontWarn,
};
*state = if op.node == BinOpKind::Add
&& is_integer_const(self.cx, rhs, 1)
&& *state == IncrementVisitorVarState::Initial
&& self.depth == 0
{
IncrementVisitorVarState::IncrOnce
} else {
// Assigned some other value
*state = VarState::DontWarn;
}
// Assigned some other value or assigned multiple times
IncrementVisitorVarState::DontWarn
};
}
},
ExprKind::Assign(ref lhs, _, _) if lhs.hir_id == expr.hir_id => *state = VarState::DontWarn,
ExprKind::Assign(ref lhs, _, _) if lhs.hir_id == expr.hir_id => {
*state = IncrementVisitorVarState::DontWarn
},
ExprKind::AddrOf(BorrowKind::Ref, mutability, _) if mutability == Mutability::Mut => {
*state = VarState::DontWarn
*state = IncrementVisitorVarState::DontWarn
},
_ => (),
}
}
walk_expr(self, expr);
} else if is_loop(expr) || is_conditional(expr) {
self.depth += 1;
walk_expr(self, expr);
self.depth -= 1;
return;
} else if let ExprKind::Continue(_) = expr.kind {
self.done = true;
return;
} else {
walk_expr(self, expr);
}
walk_expr(self, expr);
}
fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
NestedVisitorMap::None
}
}
/// Checks whether a variable is initialized to zero at the start of a loop.
enum InitializeVisitorState<'hir> {
Initial, // Not examined yet
Declared(Symbol), // Declared but not (yet) initialized
Initialized {
name: Symbol,
initializer: &'hir Expr<'hir>,
},
DontWarn,
}
/// Checks whether a variable is initialized at the start of a loop and not modified
/// and used after the loop.
struct InitializeVisitor<'a, 'tcx> {
cx: &'a LateContext<'tcx>, // context reference
end_expr: &'tcx Expr<'tcx>, // the for loop. Stop scanning here.
var_id: HirId,
state: VarState,
name: Option<Symbol>,
state: InitializeVisitorState<'tcx>,
depth: u32, // depth of conditional expressions
past_loop: bool,
}
impl<'a, 'tcx> InitializeVisitor<'a, 'tcx> {
fn new(cx: &'a LateContext<'tcx>, end_expr: &'tcx Expr<'tcx>, var_id: HirId) -> Self {
Self {
cx,
end_expr,
var_id,
state: InitializeVisitorState::Initial,
depth: 0,
past_loop: false,
}
}
fn get_result(&self) -> Option<(Symbol, &'tcx Expr<'tcx>)> {
if let InitializeVisitorState::Initialized { name, initializer } = self.state {
Some((name, initializer))
} else {
None
}
}
}
impl<'a, 'tcx> Visitor<'tcx> for InitializeVisitor<'a, 'tcx> {
type Map = Map<'tcx>;
fn visit_stmt(&mut self, stmt: &'tcx Stmt<'_>) {
// Look for declarations of the variable
if let StmtKind::Local(ref local) = stmt.kind {
if local.pat.hir_id == self.var_id {
if let PatKind::Binding(.., ident, _) = local.pat.kind {
self.name = Some(ident.name);
self.state = local.init.as_ref().map_or(VarState::Declared, |init| {
if is_integer_const(&self.cx, init, 0) {
VarState::Warn
} else {
VarState::Declared
}
})
}
if_chain! {
if let StmtKind::Local(ref local) = stmt.kind;
if local.pat.hir_id == self.var_id;
if let PatKind::Binding(.., ident, _) = local.pat.kind;
then {
self.state = local.init.map_or(InitializeVisitorState::Declared(ident.name), |init| {
InitializeVisitorState::Initialized {
initializer: init,
name: ident.name,
}
})
}
}
walk_stmt(self, stmt);
}
fn visit_expr(&mut self, expr: &'tcx Expr<'_>) {
if self.state == VarState::DontWarn {
if matches!(self.state, InitializeVisitorState::DontWarn) {
return;
}
if expr.hir_id == self.end_expr.hir_id {
@ -2244,45 +2474,51 @@ impl<'a, 'tcx> Visitor<'tcx> for InitializeVisitor<'a, 'tcx> {
}
// No need to visit expressions before the variable is
// declared
if self.state == VarState::IncrOnce {
if matches!(self.state, InitializeVisitorState::Initial) {
return;
}
// If node is the desired variable, see how it's used
if var_def_id(self.cx, expr) == Some(self.var_id) {
if self.past_loop {
self.state = InitializeVisitorState::DontWarn;
return;
}
if let Some(parent) = get_parent_expr(self.cx, expr) {
match parent.kind {
ExprKind::AssignOp(_, ref lhs, _) if lhs.hir_id == expr.hir_id => {
self.state = VarState::DontWarn;
self.state = InitializeVisitorState::DontWarn;
},
ExprKind::Assign(ref lhs, ref rhs, _) if lhs.hir_id == expr.hir_id => {
self.state = if is_integer_const(&self.cx, rhs, 0) && self.depth == 0 {
VarState::Warn
} else {
VarState::DontWarn
self.state = if_chain! {
if self.depth == 0;
if let InitializeVisitorState::Declared(name)
| InitializeVisitorState::Initialized { name, ..} = self.state;
then {
InitializeVisitorState::Initialized { initializer: rhs, name }
} else {
InitializeVisitorState::DontWarn
}
}
},
ExprKind::AddrOf(BorrowKind::Ref, mutability, _) if mutability == Mutability::Mut => {
self.state = VarState::DontWarn
self.state = InitializeVisitorState::DontWarn
},
_ => (),
}
}
if self.past_loop {
self.state = VarState::DontWarn;
return;
}
walk_expr(self, expr);
} else if !self.past_loop && is_loop(expr) {
self.state = VarState::DontWarn;
return;
self.state = InitializeVisitorState::DontWarn;
} else if is_conditional(expr) {
self.depth += 1;
walk_expr(self, expr);
self.depth -= 1;
return;
} else {
walk_expr(self, expr);
}
walk_expr(self, expr);
}
fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {

2
clippy_lints/src/utils/mod.rs
View file

@ -708,7 +708,7 @@ fn reindent_multiline_inner(s: &str, ignore_first: bool, indent: Option<usize>,
}
/// Gets the parent expression, if any –- this is useful to constrain a lint.
pub fn get_parent_expr<'c>(cx: &'c LateContext<'_>, e: &Expr<'_>) -> Option<&'c Expr<'c>> {
pub fn get_parent_expr<'tcx>(cx: &LateContext<'tcx>, e: &Expr<'_>) -> Option<&'tcx Expr<'tcx>> {
let map = &cx.tcx.hir();
let hir_id = e.hir_id;
let parent_id = map.get_parent_node(hir_id);

59
clippy_lints/src/utils/sugg.rs
View file

@ -13,8 +13,10 @@ use rustc_span::{BytePos, Pos};
use std::borrow::Cow;
use std::convert::TryInto;
use std::fmt::Display;
use std::ops::{Add, Neg, Not, Sub};
/// A helper type to build suggestion correctly handling parenthesis.
#[derive(Clone, PartialEq)]
pub enum Sugg<'a> {
/// An expression that never needs parenthesis such as `1337` or `[0; 42]`.
NonParen(Cow<'a, str>),
@ -25,8 +27,12 @@ pub enum Sugg<'a> {
BinOp(AssocOp, Cow<'a, str>),
}
/// Literal constant `0`, for convenience.
pub const ZERO: Sugg<'static> = Sugg::NonParen(Cow::Borrowed("0"));
/// Literal constant `1`, for convenience.
pub const ONE: Sugg<'static> = Sugg::NonParen(Cow::Borrowed("1"));
/// a constant represents an empty string, for convenience.
pub const EMPTY: Sugg<'static> = Sugg::NonParen(Cow::Borrowed(""));
impl Display for Sugg<'_> {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> Result<(), std::fmt::Error> {
@ -267,21 +273,60 @@ impl<'a> Sugg<'a> {
}
}
impl<'a, 'b> std::ops::Add<Sugg<'b>> for Sugg<'a> {
// Copied from the rust standart library, and then edited
macro_rules! forward_binop_impls_to_ref {
(impl $imp:ident, $method:ident for $t:ty, type Output = $o:ty) => {
impl $imp<$t> for &$t {
type Output = $o;
fn $method(self, other: $t) -> $o {
$imp::$method(self, &other)
}
}
impl $imp<&$t> for $t {
type Output = $o;
fn $method(self, other: &$t) -> $o {
$imp::$method(&self, other)
}
}
impl $imp for $t {
type Output = $o;
fn $method(self, other: $t) -> $o {
$imp::$method(&self, &other)
}
}
};
}
impl Add for &Sugg<'_> {
type Output = Sugg<'static>;
fn add(self, rhs: Sugg<'b>) -> Sugg<'static> {
make_binop(ast::BinOpKind::Add, &self, &rhs)
fn add(self, rhs: &Sugg<'_>) -> Sugg<'static> {
make_binop(ast::BinOpKind::Add, self, rhs)
}
}
impl<'a, 'b> std::ops::Sub<Sugg<'b>> for Sugg<'a> {
impl Sub for &Sugg<'_> {
type Output = Sugg<'static>;
fn sub(self, rhs: Sugg<'b>) -> Sugg<'static> {
make_binop(ast::BinOpKind::Sub, &self, &rhs)
fn sub(self, rhs: &Sugg<'_>) -> Sugg<'static> {
make_binop(ast::BinOpKind::Sub, self, rhs)
}
}
impl<'a> std::ops::Not for Sugg<'a> {
forward_binop_impls_to_ref!(impl Add, add for Sugg<'_>, type Output = Sugg<'static>);
forward_binop_impls_to_ref!(impl Sub, sub for Sugg<'_>, type Output = Sugg<'static>);
impl Neg for Sugg<'_> {
type Output = Sugg<'static>;
fn neg(self) -> Sugg<'static> {
make_unop("-", self)
}
}
impl Not for Sugg<'_> {
type Output = Sugg<'static>;
fn not(self) -> Sugg<'static> {
make_unop("!", self)

88
tests/ui/manual_memcpy.stderr
View file

@ -1,88 +0,0 @@
error: it looks like you're manually copying between slices
--> $DIR/manual_memcpy.rs:7:14
|
LL | for i in 0..src.len() {
| ^^^^^^^^^^^^ help: try replacing the loop by: `dst[..src.len()].clone_from_slice(&src[..])`
|
= note: `-D clippy::manual-memcpy` implied by `-D warnings`
error: it looks like you're manually copying between slices
--> $DIR/manual_memcpy.rs:12:14
|
LL | for i in 0..src.len() {
| ^^^^^^^^^^^^ help: try replacing the loop by: `dst[10..(src.len() + 10)].clone_from_slice(&src[..])`
error: it looks like you're manually copying between slices
--> $DIR/manual_memcpy.rs:17:14
|
LL | for i in 0..src.len() {
| ^^^^^^^^^^^^ help: try replacing the loop by: `dst[..src.len()].clone_from_slice(&src[10..])`
error: it looks like you're manually copying between slices
--> $DIR/manual_memcpy.rs:22:14
|
LL | for i in 11..src.len() {
| ^^^^^^^^^^^^^ help: try replacing the loop by: `dst[11..src.len()].clone_from_slice(&src[(11 - 10)..(src.len() - 10)])`
error: it looks like you're manually copying between slices
--> $DIR/manual_memcpy.rs:27:14
|
LL | for i in 0..dst.len() {
| ^^^^^^^^^^^^ help: try replacing the loop by: `dst.clone_from_slice(&src[..dst.len()])`
error: it looks like you're manually copying between slices
--> $DIR/manual_memcpy.rs:40:14
|
LL | for i in 10..256 {
| ^^^^^^^
|
help: try replacing the loop by
|
LL | for i in dst[10..256].clone_from_slice(&src[(10 - 5)..(256 - 5)])
LL | dst2[(10 + 500)..(256 + 500)].clone_from_slice(&src[10..256]) {
|
error: it looks like you're manually copying between slices
--> $DIR/manual_memcpy.rs:52:14
|
LL | for i in 10..LOOP_OFFSET {
| ^^^^^^^^^^^^^^^ help: try replacing the loop by: `dst[(10 + LOOP_OFFSET)..(LOOP_OFFSET + LOOP_OFFSET)].clone_from_slice(&src[(10 - some_var)..(LOOP_OFFSET - some_var)])`
error: it looks like you're manually copying between slices
--> $DIR/manual_memcpy.rs:65:14
|
LL | for i in 0..src_vec.len() {
| ^^^^^^^^^^^^^^^^ help: try replacing the loop by: `dst_vec[..src_vec.len()].clone_from_slice(&src_vec[..])`
error: it looks like you're manually copying between slices
--> $DIR/manual_memcpy.rs:94:14
|
LL | for i in from..from + src.len() {
| ^^^^^^^^^^^^^^^^^^^^^^ help: try replacing the loop by: `dst[from..from + src.len()].clone_from_slice(&src[..(from + src.len() - from)])`
error: it looks like you're manually copying between slices
--> $DIR/manual_memcpy.rs:98:14
|
LL | for i in from..from + 3 {
| ^^^^^^^^^^^^^^ help: try replacing the loop by: `dst[from..from + 3].clone_from_slice(&src[..(from + 3 - from)])`
error: it looks like you're manually copying between slices
--> $DIR/manual_memcpy.rs:103:14
|
LL | for i in 0..5 {
| ^^^^ help: try replacing the loop by: `dst[..5].clone_from_slice(&src[..5])`
error: it looks like you're manually copying between slices
--> $DIR/manual_memcpy.rs:108:14
|
LL | for i in 0..0 {
| ^^^^ help: try replacing the loop by: `dst[..0].clone_from_slice(&src[..0])`
error: it looks like you're manually copying between slices
--> $DIR/manual_memcpy.rs:120:14
|
LL | for i in 0..src.len() {
| ^^^^^^^^^^^^ help: try replacing the loop by: `dst[..src.len()].clone_from_slice(&src[..])`
error: aborting due to 13 previous errors

88
tests/ui/manual_memcpy/with_loop_counters.rs Normal file
View file

@ -0,0 +1,88 @@
#![warn(clippy::needless_range_loop, clippy::manual_memcpy)]
pub fn manual_copy_with_counters(src: &[i32], dst: &mut [i32], dst2: &mut [i32]) {
let mut count = 0;
for i in 3..src.len() {
dst[i] = src[count];
count += 1;
}
let mut count = 0;
for i in 3..src.len() {
dst[count] = src[i];
count += 1;
}
let mut count = 3;
for i in 0..src.len() {
dst[count] = src[i];
count += 1;
}
let mut count = 3;
for i in 0..src.len() {
dst[i] = src[count];
count += 1;
}
let mut count = 0;
for i in 3..(3 + src.len()) {
dst[i] = src[count];
count += 1;
}
let mut count = 3;
for i in 5..src.len() {
dst[i] = src[count - 2];
count += 1;
}
let mut count = 2;
for i in 0..dst.len() {
dst[i] = src[count];
count += 1;
}
let mut count = 5;
for i in 3..10 {
dst[i] = src[count];
count += 1;
}
let mut count = 3;
let mut count2 = 30;
for i in 0..src.len() {
dst[count] = src[i];
dst2[count2] = src[i];
count += 1;
count2 += 1;
}
// make sure parentheses are added properly to bitwise operators, which have lower precedence than
// arithmetric ones
let mut count = 0 << 1;
for i in 0..1 << 1 {
dst[count] = src[i + 2];
count += 1;
}
// make sure incrementing expressions without semicolons at the end of loops are handled correctly.
let mut count = 0;
for i in 3..src.len() {
dst[i] = src[count];
count += 1
}
// make sure ones where the increment is not at the end of the loop.
// As a possible enhancement, one could adjust the offset in the suggestion according to
// the position. For example, if the increment is at the top of the loop;
// treating the loop counter as if it were initialized 1 greater than the original value.
let mut count = 0;
#[allow(clippy::needless_range_loop)]
for i in 0..src.len() {
count += 1;
dst[i] = src[count];
}
}
fn main() {}

111
tests/ui/manual_memcpy/with_loop_counters.stderr Normal file
View file

@ -0,0 +1,111 @@
error: it looks like you're manually copying between slices
--> $DIR/with_loop_counters.rs:5:5
|
LL | / for i in 3..src.len() {
LL | | dst[i] = src[count];
LL | | count += 1;
LL | | }
| |_____^ help: try replacing the loop by: `dst[3..src.len()].clone_from_slice(&src[..(src.len() - 3)]);`
|
= note: `-D clippy::manual-memcpy` implied by `-D warnings`
error: it looks like you're manually copying between slices
--> $DIR/with_loop_counters.rs:11:5
|
LL | / for i in 3..src.len() {
LL | | dst[count] = src[i];
LL | | count += 1;
LL | | }
| |_____^ help: try replacing the loop by: `dst[..(src.len() - 3)].clone_from_slice(&src[3..]);`
error: it looks like you're manually copying between slices
--> $DIR/with_loop_counters.rs:17:5
|
LL | / for i in 0..src.len() {
LL | | dst[count] = src[i];
LL | | count += 1;
LL | | }
| |_____^ help: try replacing the loop by: `dst[3..(src.len() + 3)].clone_from_slice(&src[..]);`
error: it looks like you're manually copying between slices
--> $DIR/with_loop_counters.rs:23:5
|
LL | / for i in 0..src.len() {
LL | | dst[i] = src[count];
LL | | count += 1;
LL | | }
| |_____^ help: try replacing the loop by: `dst[..src.len()].clone_from_slice(&src[3..(src.len() + 3)]);`
error: it looks like you're manually copying between slices
--> $DIR/with_loop_counters.rs:29:5
|
LL | / for i in 3..(3 + src.len()) {
LL | | dst[i] = src[count];
LL | | count += 1;
LL | | }
| |_____^ help: try replacing the loop by: `dst[3..((3 + src.len()))].clone_from_slice(&src[..((3 + src.len()) - 3)]);`
error: it looks like you're manually copying between slices
--> $DIR/with_loop_counters.rs:35:5
|
LL | / for i in 5..src.len() {
LL | | dst[i] = src[count - 2];
LL | | count += 1;
LL | | }
| |_____^ help: try replacing the loop by: `dst[5..src.len()].clone_from_slice(&src[(3 - 2)..((src.len() - 2) + 3 - 5)]);`
error: it looks like you're manually copying between slices
--> $DIR/with_loop_counters.rs:41:5
|
LL | / for i in 0..dst.len() {
LL | | dst[i] = src[count];
LL | | count += 1;
LL | | }
| |_____^ help: try replacing the loop by: `dst.clone_from_slice(&src[2..(dst.len() + 2)]);`
error: it looks like you're manually copying between slices
--> $DIR/with_loop_counters.rs:47:5
|
LL | / for i in 3..10 {
LL | | dst[i] = src[count];
LL | | count += 1;
LL | | }
| |_____^ help: try replacing the loop by: `dst[3..10].clone_from_slice(&src[5..(10 + 5 - 3)]);`
error: it looks like you're manually copying between slices
--> $DIR/with_loop_counters.rs:54:5
|
LL | / for i in 0..src.len() {
LL | | dst[count] = src[i];
LL | | dst2[count2] = src[i];
LL | | count += 1;
LL | | count2 += 1;
LL | | }
| |_____^
|
help: try replacing the loop by
|
LL | dst[3..(src.len() + 3)].clone_from_slice(&src[..]);
LL | dst2[30..(src.len() + 30)].clone_from_slice(&src[..]);
|
error: it looks like you're manually copying between slices
--> $DIR/with_loop_counters.rs:64:5
|
LL | / for i in 0..1 << 1 {
LL | | dst[count] = src[i + 2];
LL | | count += 1;
LL | | }
| |_____^ help: try replacing the loop by: `dst[(0 << 1)..((1 << 1) + (0 << 1))].clone_from_slice(&src[2..((1 << 1) + 2)]);`
error: it looks like you're manually copying between slices
--> $DIR/with_loop_counters.rs:71:5
|
LL | / for i in 3..src.len() {
LL | | dst[i] = src[count];
LL | | count += 1
LL | | }
| |_____^ help: try replacing the loop by: `dst[3..src.len()].clone_from_slice(&src[..(src.len() - 3)]);`
error: aborting due to 11 previous errors

0
tests/ui/manual_memcpy.rs → tests/ui/manual_memcpy/without_loop_counters.rs
View file

115
tests/ui/manual_memcpy/without_loop_counters.stderr Normal file
View file

@ -0,0 +1,115 @@
error: it looks like you're manually copying between slices
--> $DIR/without_loop_counters.rs:7:5
|
LL | / for i in 0..src.len() {
LL | | dst[i] = src[i];
LL | | }
| |_____^ help: try replacing the loop by: `dst[..src.len()].clone_from_slice(&src[..]);`
|
= note: `-D clippy::manual-memcpy` implied by `-D warnings`
error: it looks like you're manually copying between slices
--> $DIR/without_loop_counters.rs:12:5
|
LL | / for i in 0..src.len() {
LL | | dst[i + 10] = src[i];
LL | | }
| |_____^ help: try replacing the loop by: `dst[10..(src.len() + 10)].clone_from_slice(&src[..]);`
error: it looks like you're manually copying between slices
--> $DIR/without_loop_counters.rs:17:5
|
LL | / for i in 0..src.len() {
LL | | dst[i] = src[i + 10];
LL | | }
| |_____^ help: try replacing the loop by: `dst[..src.len()].clone_from_slice(&src[10..(src.len() + 10)]);`
error: it looks like you're manually copying between slices
--> $DIR/without_loop_counters.rs:22:5
|
LL | / for i in 11..src.len() {
LL | | dst[i] = src[i - 10];
LL | | }
| |_____^ help: try replacing the loop by: `dst[11..src.len()].clone_from_slice(&src[(11 - 10)..(src.len() - 10)]);`
error: it looks like you're manually copying between slices
--> $DIR/without_loop_counters.rs:27:5
|
LL | / for i in 0..dst.len() {
LL | | dst[i] = src[i];
LL | | }
| |_____^ help: try replacing the loop by: `dst.clone_from_slice(&src[..dst.len()]);`
error: it looks like you're manually copying between slices
--> $DIR/without_loop_counters.rs:40:5
|
LL | / for i in 10..256 {
LL | | dst[i] = src[i - 5];
LL | | dst2[i + 500] = src[i]
LL | | }
| |_____^
|
help: try replacing the loop by
|
LL | dst[10..256].clone_from_slice(&src[(10 - 5)..(256 - 5)]);
LL | dst2[(10 + 500)..(256 + 500)].clone_from_slice(&src[10..256]);
|
error: it looks like you're manually copying between slices
--> $DIR/without_loop_counters.rs:52:5
|
LL | / for i in 10..LOOP_OFFSET {
LL | | dst[i + LOOP_OFFSET] = src[i - some_var];
LL | | }
| |_____^ help: try replacing the loop by: `dst[(10 + LOOP_OFFSET)..(LOOP_OFFSET + LOOP_OFFSET)].clone_from_slice(&src[(10 - some_var)..(LOOP_OFFSET - some_var)]);`
error: it looks like you're manually copying between slices
--> $DIR/without_loop_counters.rs:65:5
|
LL | / for i in 0..src_vec.len() {
LL | | dst_vec[i] = src_vec[i];
LL | | }
| |_____^ help: try replacing the loop by: `dst_vec[..src_vec.len()].clone_from_slice(&src_vec[..]);`
error: it looks like you're manually copying between slices
--> $DIR/without_loop_counters.rs:94:5
|
LL | / for i in from..from + src.len() {
LL | | dst[i] = src[i - from];
LL | | }
| |_____^ help: try replacing the loop by: `dst[from..(from + src.len())].clone_from_slice(&src[..(from + src.len() - from)]);`
error: it looks like you're manually copying between slices
--> $DIR/without_loop_counters.rs:98:5
|
LL | / for i in from..from + 3 {
LL | | dst[i] = src[i - from];
LL | | }
| |_____^ help: try replacing the loop by: `dst[from..(from + 3)].clone_from_slice(&src[..(from + 3 - from)]);`
error: it looks like you're manually copying between slices
--> $DIR/without_loop_counters.rs:103:5
|
LL | / for i in 0..5 {
LL | | dst[i - 0] = src[i];
LL | | }
| |_____^ help: try replacing the loop by: `dst[..5].clone_from_slice(&src[..5]);`
error: it looks like you're manually copying between slices
--> $DIR/without_loop_counters.rs:108:5
|
LL | / for i in 0..0 {
LL | | dst[i] = src[i];
LL | | }
| |_____^ help: try replacing the loop by: `dst[..0].clone_from_slice(&src[..0]);`
error: it looks like you're manually copying between slices
--> $DIR/without_loop_counters.rs:120:5
|
LL | / for i in 0..src.len() {
LL | | dst[i] = src[i].clone();
LL | | }
| |_____^ help: try replacing the loop by: `dst[..src.len()].clone_from_slice(&src[..]);`
error: aborting due to 13 previous errors