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Auto merge of #7690 - Jarcho:while_loop_by_ref, r=xFrednet

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Change `while_let_on_iterator` suggestion to use `by_ref()`

It came up in the discussion #7659 that suggesting `iter.by_ref()` is a clearer suggestion than `&mut iter`. I personally think they're equivalent, but if `by_ref()` is clearer to people then that should be the suggestion.

changelog: Change `while_let_on_iterator` suggestion when using `&mut` to use `by_ref()`
This commit is contained in:
bors 2021-09-19 17:37:04 +00:00
commit 871ad80bb0
3 changed files with 22 additions and 27 deletions
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13
clippy_lints/src/loops/while_let_on_iterator.rs
View file

@ -8,7 +8,7 @@ use clippy_utils::{
use if_chain::if_chain;
use rustc_errors::Applicability;
use rustc_hir::intravisit::{walk_expr, ErasedMap, NestedVisitorMap, Visitor};
use rustc_hir::{def::Res, Expr, ExprKind, HirId, Local, Mutability, PatKind, QPath, UnOp};
use rustc_hir::{def::Res, Expr, ExprKind, HirId, Local, PatKind, QPath, UnOp};
use rustc_lint::LateContext;
use rustc_span::{symbol::sym, Span, Symbol};
@ -47,13 +47,8 @@ pub(super) fn check(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
// If the iterator is a field or the iterator is accessed after the loop is complete it needs to be
// borrowed mutably. TODO: If the struct can be partially moved from and the struct isn't used
// afterwards a mutable borrow of a field isn't necessary.
let ref_mut = if !iter_expr.fields.is_empty() || needs_mutable_borrow(cx, &iter_expr, loop_expr) {
if cx.typeck_results().node_type(iter_expr.hir_id).ref_mutability() == Some(Mutability::Mut) {
// Reborrow for mutable references. It may not be possible to get a mutable reference here.
"&mut *"
} else {
"&mut "
}
let by_ref = if !iter_expr.fields.is_empty() || needs_mutable_borrow(cx, &iter_expr, loop_expr) {
".by_ref()"
} else {
""
};
@ -65,7 +60,7 @@ pub(super) fn check(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
expr.span.with_hi(scrutinee_expr.span.hi()),
"this loop could be written as a `for` loop",
"try",
format!("for {} in {}{}", loop_var, ref_mut, iterator),
format!("for {} in {}{}", loop_var, iterator, by_ref),
applicability,
);
}

18
tests/ui/while_let_on_iterator.fixed
View file

@ -188,7 +188,7 @@ fn issue6491() {
// Used in outer loop, needs &mut
let mut it = 1..40;
while let Some(n) = it.next() {
for m in &mut it {
for m in it.by_ref() {
if m % 10 == 0 {
break;
}
@ -219,7 +219,7 @@ fn issue6491() {
// Used after the loop, needs &mut.
let mut it = 1..40;
for m in &mut it {
for m in it.by_ref() {
if m % 10 == 0 {
break;
}
@ -236,7 +236,7 @@ fn issue6231() {
let mut it = 1..40;
let mut opt = Some(0);
while let Some(n) = opt.take().or_else(|| it.next()) {
for m in &mut it {
for m in it.by_ref() {
if n % 10 == 0 {
break;
}
@ -251,7 +251,7 @@ fn issue1924() {
impl<T: Iterator<Item = u32>> S<T> {
fn f(&mut self) -> Option<u32> {
// Used as a field.
for i in &mut self.0 {
for i in self.0.by_ref() {
if !(3..=7).contains(&i) {
return Some(i);
}
@ -283,7 +283,7 @@ fn issue1924() {
}
}
// This one is fine, a different field is borrowed
for i in &mut self.0.0.0 {
for i in self.0.0.0.by_ref() {
if i == 1 {
return self.0.1.take();
} else {
@ -312,7 +312,7 @@ fn issue1924() {
// Needs &mut, field of the iterator is accessed after the loop
let mut it = S2(1..40, 0);
for n in &mut it {
for n in it.by_ref() {
if n == 0 {
break;
}
@ -324,7 +324,7 @@ fn issue7249() {
let mut it = 0..10;
let mut x = || {
// Needs &mut, the closure can be called multiple times
for x in &mut it {
for x in it.by_ref() {
if x % 2 == 0 {
break;
}
@ -338,7 +338,7 @@ fn issue7510() {
let mut it = 0..10;
let it = &mut it;
// Needs to reborrow `it` as the binding isn't mutable
for x in &mut *it {
for x in it.by_ref() {
if x % 2 == 0 {
break;
}
@ -349,7 +349,7 @@ fn issue7510() {
let mut it = 0..10;
let it = S(&mut it);
// Needs to reborrow `it.0` as the binding isn't mutable
for x in &mut *it.0 {
for x in it.0.by_ref() {
if x % 2 == 0 {
break;
}

18
tests/ui/while_let_on_iterator.stderr
View file

@ -46,7 +46,7 @@ error: this loop could be written as a `for` loop
--> $DIR/while_let_on_iterator.rs:191:9
|
LL | while let Some(m) = it.next() {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for m in &mut it`
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for m in it.by_ref()`
error: this loop could be written as a `for` loop
--> $DIR/while_let_on_iterator.rs:202:5
@ -70,19 +70,19 @@ error: this loop could be written as a `for` loop
--> $DIR/while_let_on_iterator.rs:222:9
|
LL | while let Some(m) = it.next() {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for m in &mut it`
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for m in it.by_ref()`
error: this loop could be written as a `for` loop
--> $DIR/while_let_on_iterator.rs:239:9
|
LL | while let Some(m) = it.next() {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for m in &mut it`
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for m in it.by_ref()`
error: this loop could be written as a `for` loop
--> $DIR/while_let_on_iterator.rs:254:13
|
LL | while let Some(i) = self.0.next() {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for i in &mut self.0`
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for i in self.0.by_ref()`
error: manual `!RangeInclusive::contains` implementation
--> $DIR/while_let_on_iterator.rs:255:20
@ -96,31 +96,31 @@ error: this loop could be written as a `for` loop
--> $DIR/while_let_on_iterator.rs:286:13
|
LL | while let Some(i) = self.0.0.0.next() {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for i in &mut self.0.0.0`
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for i in self.0.0.0.by_ref()`
error: this loop could be written as a `for` loop
--> $DIR/while_let_on_iterator.rs:315:5
|
LL | while let Some(n) = it.next() {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for n in &mut it`
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for n in it.by_ref()`
error: this loop could be written as a `for` loop
--> $DIR/while_let_on_iterator.rs:327:9
|
LL | while let Some(x) = it.next() {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for x in &mut it`
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for x in it.by_ref()`
error: this loop could be written as a `for` loop
--> $DIR/while_let_on_iterator.rs:341:5
|
LL | while let Some(x) = it.next() {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for x in &mut *it`
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for x in it.by_ref()`
error: this loop could be written as a `for` loop
--> $DIR/while_let_on_iterator.rs:352:5
|
LL | while let Some(x) = it.0.next() {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for x in &mut *it.0`
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `for x in it.0.by_ref()`
error: this loop could be written as a `for` loop
--> $DIR/while_let_on_iterator.rs:371:5