rust/tests/ui/while_loop.rs

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#![warn(while_let_loop, empty_loop, while_let_on_iterator)]
#![allow(dead_code, never_loop, unused, cyclomatic_complexity)]
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fn main() {
let y = Some(true);
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loop {
if let Some(_x) = y {
let _v = 1;
} else {
break
}
}
loop { // no error, break is not in else clause
if let Some(_x) = y {
let _v = 1;
}
break;
}
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loop {
match y {
Some(_x) => true,
None => break
};
}
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loop {
let x = match y {
Some(x) => x,
None => break
};
let _x = x;
let _str = "foo";
}
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loop {
let x = match y {
Some(x) => x,
None => break,
};
{ let _a = "bar"; };
{ let _b = "foobar"; }
}
loop { // no error, else branch does something other than break
match y {
Some(_x) => true,
_ => {
let _z = 1;
break;
}
};
}
while let Some(x) = y { // no error, obviously
println!("{}", x);
}
// #675, this used to have a wrong suggestion
loop {
let (e, l) = match "".split_whitespace().next() {
Some(word) => (word.is_empty(), word.len()),
None => break
};
let _ = (e, l);
}
let mut iter = 1..20;
while let Option::Some(x) = iter.next() {
println!("{}", x);
}
let mut iter = 1..20;
while let Some(x) = iter.next() {
println!("{}", x);
}
let mut iter = 1..20;
while let Some(_) = iter.next() {}
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let mut iter = 1..20;
while let None = iter.next() {} // this is fine (if nonsensical)
let mut iter = 1..20;
if let Some(x) = iter.next() { // also fine
println!("{}", x)
}
// the following shouldn't warn because it can't be written with a for loop
let mut iter = 1u32..20;
while let Some(x) = iter.next() {
println!("next: {:?}", iter.next())
}
// neither can this
let mut iter = 1u32..20;
while let Some(x) = iter.next() {
println!("next: {:?}", iter.next());
}
// or this
let mut iter = 1u32..20;
while let Some(x) = iter.next() {break;}
println!("Remaining iter {:?}", iter);
// or this
let mut iter = 1u32..20;
while let Some(x) = iter.next() {
iter = 1..20;
}
}
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// regression test (#360)
// this should not panic
// it's okay if further iterations of the lint
// cause this function to trigger it
fn no_panic<T>(slice: &[T]) {
let mut iter = slice.iter();
loop {
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let _ = match iter.next() {
Some(ele) => ele,
None => break
};
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loop {}
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}
}
fn issue1017() {
let r: Result<u32, u32> = Ok(42);
let mut len = 1337;
loop {
match r {
Err(_) => len = 0,
Ok(length) => {
len = length;
break
}
}
}
}
// Issue #1188
fn refutable() {
let a = [42, 1337];
let mut b = a.iter();
// consume all the 42s
while let Some(&42) = b.next() {
}
let a = [(1, 2, 3)];
let mut b = a.iter();
while let Some(&(1, 2, 3)) = b.next() {
}
let a = [Some(42)];
let mut b = a.iter();
while let Some(&None) = b.next() {
}
/* This gives “refutable pattern in `for` loop binding: `&_` not covered”
for &42 in b {}
for &(1, 2, 3) in b {}
for &Option::None in b.next() {}
// */
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let mut y = a.iter();
loop { // x is reused, so don't lint here
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while let Some(v) = y.next() {
}
}
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let mut y = a.iter();
for _ in 0..2 {
while let Some(v) = y.next() { // y is reused, don't lint
}
}
loop {
let mut y = a.iter();
while let Some(v) = y.next() { // use a for loop here
}
}
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// should not trigger while_let_loop lint because break passes an expression
let a = Some(10);
let b = loop {
if let Some(c) = a {
break Some(c);
} else {
break None;
}
};
}