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Diffstat (limited to '')
-rw-r--r-- | src/test/ui/typeck/issue-73592-borrow_mut-through-deref.rs | 59 |
1 files changed, 59 insertions, 0 deletions
diff --git a/src/test/ui/typeck/issue-73592-borrow_mut-through-deref.rs b/src/test/ui/typeck/issue-73592-borrow_mut-through-deref.rs new file mode 100644 index 000000000..3b399e629 --- /dev/null +++ b/src/test/ui/typeck/issue-73592-borrow_mut-through-deref.rs @@ -0,0 +1,59 @@ +// check-pass +// run-rustfix +// +// rust-lang/rust#73592: borrow_mut through Deref should work. +// +// Before #72280, when we see something like `&mut *rcvr.method()`, we +// incorrectly requires `rcvr` to be type-checked as a mut place. While this +// requirement is usually correct for smart pointers, it is overly restrictive +// for types like `Mutex` or `RefCell` which can produce a guard that +// implements `DerefMut` from `&self`. +// +// Making it more confusing, because we use Deref as the fallback when DerefMut +// is implemented, we won't see an issue when the smart pointer does not +// implement `DerefMut`. It only causes an issue when `rcvr` is obtained via a +// type that implements both `Deref` or `DerefMut`. +// +// This bug is only discovered in #73592 after it is already fixed as a side-effect +// of a refactoring made in #72280. + +#![warn(unused_mut)] + +use std::pin::Pin; +use std::cell::RefCell; + +struct S(RefCell<()>); + +fn test_pin(s: Pin<&S>) { + // This works before #72280. + let _ = &mut *s.0.borrow_mut(); +} + +fn test_pin_mut(s: Pin<&mut S>) { + // This should compile but didn't before #72280. + let _ = &mut *s.0.borrow_mut(); +} + +fn test_vec(s: &Vec<RefCell<()>>) { + // This should compile but didn't before #72280. + let _ = &mut *s[0].borrow_mut(); +} + +fn test_mut_pin(mut s: Pin<&S>) { + //~^ WARN variable does not need to be mutable + let _ = &mut *s.0.borrow_mut(); +} + +fn test_mut_pin_mut(mut s: Pin<&mut S>) { + //~^ WARN variable does not need to be mutable + let _ = &mut *s.0.borrow_mut(); +} + +fn main() { + let mut s = S(RefCell::new(())); + test_pin(Pin::new(&s)); + test_pin_mut(Pin::new(&mut s)); + test_mut_pin(Pin::new(&s)); + test_mut_pin_mut(Pin::new(&mut s)); + test_vec(&vec![s.0]); +} |