Rust errors / Types and traits
Rust compiler error · checked with rustc 1.99.0
Rust error E0600: cannot apply unary operator `!` to type `Question`
What it meansAn unary operator was used on a type which doesn't implement it.
What rustc prints
error[E0600]: cannot apply unary operator `!` to type `Question` --> main.rs:8:1 | 8 | !Question::Yes; // error: cannot apply unary operator `!` to type `Question` | ^^^^^^^^^^^^^^ cannot apply unary operator `!` | note: an implementation of `Not` might be missing for `Question` --> main.rs:3:1 | 3 | enum Question { | ^^^^^^^^^^^^^ must implement `Not` note: the trait `Not` must be implemented --> /rustc/b940084d7eb6a299eb4bfeb8e34901bc051e7ac4/library\core\src\ops\bit.rs:35:0
Real output of rustc 1.99.0 compiling the official example below (2021 edition). Your names and line numbers will differ; the first line is the part to match.
E0600Types and traits
Activein rustc 1.99.0
7related errors linked below
The compiler team's explanation
An unary operator was used on a type which doesn't implement it.
Erroneous code example:
enum Question {
Yes,
No,
}
!Question::Yes; // error: cannot apply unary operator `!` to type `Question`In this case, Question would need to implement the std::ops::Not trait in order to be able to use ! on it. Let's implement it:
use std::ops::Not;
enum Question {
Yes,
No,
}
// We implement the `Not` trait on the enum.
impl Not for Question {
type Output = bool;
fn not(self) -> bool {
match self {
Question::Yes => false, // If the `Answer` is `Yes`, then it
// returns false.
Question::No => true, // And here we do the opposite.
}
}
}
assert_eq!(!Question::Yes, false);
assert_eq!(!Question::No, true);From rustc --explain E0600 (1.99.0), part of the Rust project, MIT or Apache-2.0. Official page.
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