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Add comment on why RefCell::unwrap is safe. #19137

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Nov 23, 2014
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Add comment on why RefCell::unwrap is safe. #19137

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3 changes: 3 additions & 0 deletions src/libcore/cell.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -258,6 +258,9 @@ impl<T> RefCell<T> {
/// Consumes the `RefCell`, returning the wrapped value.
#[unstable = "may be renamed, depending on global conventions"]
pub fn unwrap(self) -> T {
// Since this function takes `self` (the `RefCell`) by value, the
// compiler statically verifies that it is not currently borrowed.
// Therefore the following assertion is just a `debug_assert!`.
debug_assert!(self.borrow.get() == UNUSED);
unsafe{self.value.unwrap()}
}
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