Keyboard shortcuts

Press ← or → to navigate between chapters

Press S or / to search in the book

Press ? to show this help

Press Esc to hide this help

Refutability

A pattern which matches all values of its type is irrefutable while one which only matches conditionally is refutable.

For example, a pattern unpacking a tuple is irrefutable because all values of type (T, Y) will match (a, b)

let tuple: (T, Y) = ...;

match tuple {
    (a, b) => {...}
}

while one which matches an enum variant is refutable because the None option will not match

enum Option<T> {
    Some{val: T},
    None,
}

match x {
    Some(x) => {...} // refutable: None not covered
    ...
}