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Auto merge of #57927 - Alexendoo:mem-drop-nll-docs, r=Centril

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Remove lexical scope examples from std::mem::drop

The example no longer produces an error in the 2018 edition
This commit is contained in:
bors 2019-01-27 09:19:00 +00:00
commit 01af12008d
1 changed files with 1 additions and 28 deletions
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29
src/libcore/mem.rs
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@ -713,8 +713,7 @@ pub fn replace<T>(dest: &mut T, mut src: T) -> T {
/// Disposes of a value.
///
/// While this does call the argument's implementation of [`Drop`][drop],
/// it will not release any borrows, as borrows are based on lexical scope.
/// This does call the argument's implementation of [`Drop`][drop].
///
/// This effectively does nothing for types which implement `Copy`, e.g.
/// integers. Such values are copied and _then_ moved into the function, so the
@ -741,32 +740,6 @@ pub fn replace<T>(dest: &mut T, mut src: T) -> T {
/// drop(v); // explicitly drop the vector
/// ```
///
/// Borrows are based on lexical scope, so this produces an error:
///
/// ```compile_fail,E0502
/// let mut v = vec![1, 2, 3];
/// let x = &v[0];
///
/// drop(x); // explicitly drop the reference, but the borrow still exists
///
/// v.push(4); // error: cannot borrow `v` as mutable because it is also
/// // borrowed as immutable
/// ```
///
/// An inner scope is needed to fix this:
///
/// ```
/// let mut v = vec![1, 2, 3];
///
/// {
/// let x = &v[0];
///
/// drop(x); // this is now redundant, as `x` is going out of scope anyway
/// }
///
/// v.push(4); // no problems
/// ```
///
/// Since [`RefCell`] enforces the borrow rules at runtime, `drop` can
/// release a [`RefCell`] borrow:
///