I was having fun with traits in Rust and discovered, that you can create traits that cannot be implemented.
pub trait Never {
fn uncallable() {
println!("I can never be called.");
}
fn never_implemented();
}
impl<T> Never for T
where
T: Never,
{
fn never_implemented() {
println!("I am never implemented and thus cannot be called.");
}
}
pub fn test(never: impl Never) {
println!("Can't call me!");
}
fn main() {
Never::uncallable();
}
Errors:
Compiling playground v0.0.1 (/playground)
error[E0790]: cannot call associated function on trait without specifying the corresponding `impl` type
--> src/main.rs:20:5
|
2 | / fn uncallable() {
3 | | println!("I can never be called.");
4 | | }
| |_____- `Never::uncallable` defined here
...
20 | Never::uncallable();
| ^^^^^^^^^^^^^^^^^^^ cannot call associated function of trait
warning: unused variable: `never`
--> src/main.rs:15:13
|
15 | pub fn test(never: impl Never) {
| ^^^^^ help: if this is intentional, prefix it with an underscore: `_never`
|
= note: `#[warn(unused_variables)]` on by default
For more information about this error, try `rustc --explain E0790`.
warning: `playground` (bin "playground") generated 1 warning
error: could not compile `playground` (bin "playground") due to 1 previous error; 1 warning emitted
I did this just for fun and to play with the language, but it made me wonder, whether there's an actual application for traits that are never implemented....?
