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add another NLL problem case 3 variant

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This commit is contained in:
Rémy Rakic
2026-02-13 17:29:49 +00:00
parent be204dd047
commit 65eb2e709d
2 changed files with 38 additions and 5 deletions
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tests/ui/nll/polonius/nll-problem-case-3-issue-21906.nll.stderr
+18 -5
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@@ -35,8 +35,21 @@ LL | | }
LL | | }
| |_____- returning this value requires that `*map` is borrowed for `'r`
error[E0499]: cannot borrow `*map` as mutable more than once at a time
--> $DIR/nll-problem-case-3-issue-21906.rs:45:41
|
LL | fn get_priority_mut_entry<'a, K, V>(
| -- lifetime `'a` defined here
...
LL | match map.entry(key1) {
| --- first mutable borrow occurs here
LL | Entry::Occupied(occupied) => Some(occupied.into_mut()),
| ------------------------- returning this value requires that `*map` is borrowed for `'a`
LL | Entry::Vacant(_vacant) => match map.entry(key2) {
| ^^^ second mutable borrow occurs here
error[E0499]: cannot borrow `*self` as mutable more than once at a time
--> $DIR/nll-problem-case-3-issue-21906.rs:44:21
--> $DIR/nll-problem-case-3-issue-21906.rs:64:21
|
LL | fn two(&mut self) -> &i32 {
| - let's call the lifetime of this reference `'1`
@@ -48,7 +61,7 @@ LL | return k;
| - returning this value requires that `*self` is borrowed for `'1`
error[E0502]: cannot borrow `x.data` as immutable because it is also borrowed as mutable
--> $DIR/nll-problem-case-3-issue-21906.rs:62:22
--> $DIR/nll-problem-case-3-issue-21906.rs:82:22
|
LL | fn foo(x: &mut Foo) -> Option<&mut i32> {
| - let's call the lifetime of this reference `'1`
@@ -61,7 +74,7 @@ LL | println!("{:?}", x.data);
| ^^^^^^ immutable borrow occurs here
error[E0499]: cannot borrow `*vec` as mutable more than once at a time
--> $DIR/nll-problem-case-3-issue-21906.rs:77:9
--> $DIR/nll-problem-case-3-issue-21906.rs:97:9
|
LL | fn f(vec: &mut Vec<u8>) -> &u8 {
| - let's call the lifetime of this reference `'1`
@@ -75,7 +88,7 @@ LL | vec.push(10);
| ^^^ second mutable borrow occurs here
error[E0502]: cannot borrow `*vec` as immutable because it is also borrowed as mutable
--> $DIR/nll-problem-case-3-issue-21906.rs:78:9
--> $DIR/nll-problem-case-3-issue-21906.rs:98:9
|
LL | fn f(vec: &mut Vec<u8>) -> &u8 {
| - let's call the lifetime of this reference `'1`
@@ -88,7 +101,7 @@ LL | n
LL | vec.last().unwrap()
| ^^^ immutable borrow occurs here
error: aborting due to 6 previous errors
error: aborting due to 7 previous errors
Some errors have detailed explanations: E0499, E0502.
For more information about an error, try `rustc --explain E0499`.
tests/ui/nll/polonius/nll-problem-case-3-issue-21906.rs
+20
View File
@@ -29,6 +29,26 @@ fn from_the_rfc<'r, K: Hash + Eq + Copy, V: Default>(
}
}
// A variant that's similar to the RFC example above, but using the entry API, and requested in
// https://internals.rust-lang.org/t/get-mut-map-back-from-entry-api/24003
fn get_priority_mut_entry<'a, K, V>(
map: &'a mut HashMap<K, V>,
key1: K,
key2: K,
) -> Option<&'a mut V>
where
K: Eq + Hash,
{
use std::collections::hash_map::Entry;
match map.entry(key1) {
Entry::Occupied(occupied) => Some(occupied.into_mut()),
Entry::Vacant(_vacant) => match map.entry(key2) {
Entry::Occupied(occupied2) => Some(occupied2.into_mut()),
Entry::Vacant(_) => None,
},
}
}
// MCVE 1 from issue #21906
struct A {
a: i32,