Wrong path statement warning with constant implementing Drop

[tspiteri]

This program prints dropped as the constant is copied and dropped.

struct S;
impl Drop for S {
    fn drop(&mut self) {
        println!("dropped")
    }
}
const C: S = S;
fn main() {
    C;
}

That means that the statement C; does have an effect: it prints dropped. But the compiler warns that the statement has no effect:

warning: path statement with no effect
 --> src/main.rs:9:5
  |
9 |     C;
  |     ^^
  |
  = note: `#[warn(path_statements)]` on by default

(Reproduced on stable 1.43.0 and nightly 2020-05-02.)

[jonas-schievink]

Duplicate of #48852