rust/tests/ui/rfc-2361-dbg-macro/dbg-macro-expected-behavior.rs

70 lines
1.7 KiB
Rust

// run-pass
// check-run-results
// Tests ensuring that `dbg!(expr)` has the expected run-time behavior.
// as well as some compile time properties we expect.
#![allow(drop_copy)]
#[derive(Copy, Clone, Debug)]
struct Unit;
#[derive(Copy, Clone, Debug, PartialEq)]
struct Point<T> {
x: T,
y: T,
}
#[derive(Debug, PartialEq)]
struct NoCopy(usize);
fn main() {
let a: Unit = dbg!(Unit);
let _: Unit = dbg!(a);
// We can move `a` because it's Copy.
drop(a);
// `Point<T>` will be faithfully formatted according to `{:#?}`.
let a = Point { x: 42, y: 24 };
let b: Point<u8> = dbg!(Point { x: 42, y: 24 }); // test stringify!(..)
let c: Point<u8> = dbg!(b);
// Identity conversion:
assert_eq!(a, b);
assert_eq!(a, c);
// We can move `b` because it's Copy.
drop(b);
// Without parameters works as expected.
let _: () = dbg!();
// Test that we can borrow and that successive applications is still identity.
let a = NoCopy(1337);
let b: &NoCopy = dbg!(dbg!(&a));
assert_eq!(&a, b);
// Test involving lifetimes of temporaries:
fn f<'a>(x: &'a u8) -> &'a u8 { x }
let a: &u8 = dbg!(f(&42));
assert_eq!(a, &42);
// Test side effects:
let mut foo = 41;
assert_eq!(7331, dbg!({
foo += 1;
eprintln!("before");
7331
}));
assert_eq!(foo, 42);
// Test trailing comma:
assert_eq!(("Yeah",), dbg!(("Yeah",)));
// Test multiple arguments:
assert_eq!((1u8, 2u32), dbg!(1,
2));
// Test multiple arguments + trailing comma:
assert_eq!((1u8, 2u32, "Yeah"), dbg!(1u8, 2u32,
"Yeah",));
}