Detect unconditional recursion in Drop

[omarabid]

If you instantiate the same struct in the Drop function, the program will loop indefinitely and crash.

The Code

struct ToDrop;

impl Drop for ToDrop {
    fn drop(&mut self) {
        let m = ToDrop;
        println!( "ToDrop is being dropped" );
    }
}
fn main() {
    let x =  ToDrop;
}

Well, I expected the compiler to catch this at compilation. So this could be an area of improvement.

Here is another variation that also causes a stackoverflow without intializing the same variable

struct A;
struct B;

impl Drop for A {
    fn drop( &mut self ) {
        let b = B;
    }
}

impl Drop for B {
    fn drop( &mut self ) {
        let a = A;
    }
}

fn main() {
    let a = A;
}

The error message at execution

thread 'main' has overflowed its stack
fatal runtime error: stack overflow
Abort trap: 6

[oli-obk]

This might be better suited as a clippy lint

[jonas-schievink]

#55388 is a duplicate of this, but it has more information including mentoring instructions, so I'm kind of inclined to close this older issue instead