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4aba2c55e6
Start pointing to where bindings were declared when they are captured in closures:
```
error[E0597]: `x` does not live long enough
--> $DIR/suggest-return-closure.rs:23:9
|
LL | let x = String::new();
| - binding `x` declared here
...
LL | |c| {
| --- value captured here
LL | x.push(c);
| ^ borrowed value does not live long enough
...
LL | }
| -- borrow later used here
| |
| `x` dropped here while still borrowed
```
Suggest cloning in more cases involving closures:
```
error[E0507]: cannot move out of `foo` in pattern guard
--> $DIR/issue-27282-move-ref-mut-into-guard.rs:11:19
|
LL | if { (|| { let mut bar = foo; bar.take() })(); false } => {},
| ^^ --- move occurs because `foo` has type `&mut Option<&i32>`, which does not implement the `Copy` trait
| |
| `foo` is moved here
|
= note: variables bound in patterns cannot be moved from until after the end of the pattern guard
help: consider cloning the value if the performance cost is acceptable
|
LL | if { (|| { let mut bar = foo.clone(); bar.take() })(); false } => {},
| ++++++++
```
67 lines
1.8 KiB
Rust
67 lines
1.8 KiB
Rust
#![feature(if_let_guard)]
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#![allow(unused_mut)]
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//@ run-rustfix
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// Here is arielb1's basic example from rust-lang/rust#27282
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// that AST borrowck is flummoxed by:
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fn should_reject_destructive_mutate_in_guard() {
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match Some(&4) {
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None => {},
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ref mut foo if {
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(|| { let mut bar = foo; bar.take() })();
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//~^ ERROR cannot move out of `foo` in pattern guard [E0507]
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false } => { },
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Some(s) => std::process::exit(*s),
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}
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match Some(&4) {
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None => {},
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ref mut foo if let Some(()) = {
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(|| { let mut bar = foo; bar.take() })();
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//~^ ERROR cannot move out of `foo` in pattern guard [E0507]
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None } => { },
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Some(s) => std::process::exit(*s),
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}
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}
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// Here below is a case that needs to keep working: we only use the
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// binding via immutable-borrow in the guard, and we mutate in the arm
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// body.
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fn allow_mutate_in_arm_body() {
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match Some(&4) {
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None => {},
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ref mut foo if foo.is_some() => { foo.take(); () }
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Some(s) => std::process::exit(*s),
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}
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match Some(&4) {
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None => {},
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ref mut foo if let Some(_) = foo => { foo.take(); () }
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Some(s) => std::process::exit(*s),
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}
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}
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// Here below is a case that needs to keep working: we only use the
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// binding via immutable-borrow in the guard, and we move into the arm
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// body.
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fn allow_move_into_arm_body() {
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match Some(&4) {
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None => {},
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mut foo if foo.is_some() => { foo.unwrap(); () }
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Some(s) => std::process::exit(*s),
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}
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match Some(&4) {
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None => {},
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mut foo if let Some(_) = foo => { foo.unwrap(); () }
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Some(s) => std::process::exit(*s),
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}
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}
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fn main() {
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should_reject_destructive_mutate_in_guard();
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allow_mutate_in_arm_body();
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allow_move_into_arm_body();
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}
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