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Document the question mark operator

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est31 2016-11-09 07:23:57 +01:00 committed by Manish Goregaokar
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@ -2863,8 +2863,8 @@ assert_eq!(x, y);
### Unary operator expressions
Rust defines the following unary operators. They are all written as prefix operators,
before the expression they apply to.
Rust defines the following unary operators. With the exception of `?`, they are
all written as prefix operators, before the expression they apply to.
* `-`
: Negation. Signed integer types and floating-point types support negation. It
@ -2893,6 +2893,10 @@ before the expression they apply to.
If the `&` or `&mut` operators are applied to an rvalue, a
temporary value is created; the lifetime of this temporary value
is defined by [syntactic rules](#temporary-lifetimes).
* `?`
: Propagating errors if applied to `Err(_)` and unwrapping if
applied to `Ok(_)`. Only works on the `Result<T, E>` type,
and written in postfix notation.
### Binary operator expressions