Rust doesn't have -- operator, which some other languages have.
When misusing -- operator in Rust code, the compiler yields warnings as follows:
warning: variable does not need to be mutable
--> src/main.rs:2:9
|
2 | let mut dec = 10;
| ----^^^
| |
| help: remove this `mut`
|
= note: `#[warn(unused_mut)]` on by default
warning: unused unary operation that must be used
--> src/main.rs:4:9
|
4 | --dec;
| ^^^^^
|
= note: `#[warn(unused_must_use)]` on by default
warning: 2 warnings emitted
These warnings are useful to notice the operator doesn't exist, but I think it's still not a proper warning for beginners. How about a suggestion like this:
warning: -- operator doesn't exist
--> src/main.rs:4:9
|
4 | --dec;
| ^^^^^
| help: do you mean "dec -= 1;"
= note: `#[warn(unused_must_use)]` on by default