rust/tests/ui/macros/assert-format-lazy.rs

// run-pass
// compile-flags: -C debug_assertions=yes

#[allow(unreachable_code)]
fn main() {
    assert!(true, "Failed: {:?}", panic!("assert! evaluated format expressions"));
    debug_assert!(true, "Failed: {:?}", panic!("debug_assert! evaluated format expressions"));
    assert_eq!(1, 1, "Failed: {:?}", panic!("assert_eq! evaluated format expressions"));
    debug_assert_eq!(1, 1, "Failed: {:?}", panic!("debug_assert_eq! evaluated format expressions"));
    assert_ne!(1, 2, "Failed: {:?}", panic!("assert_ne! evaluated format expressions"));
    debug_assert_ne!(1, 2, "Failed: {:?}", panic!("debug_assert_ne! evaluated format expressions"));
}
Document that `assert!` format arguments are evaluated lazily It can be useful to do some computation in `assert!` format arguments, in order to get better error messages. For example: ```rust assert!( some_condition, "The state is invalid. Details: {}", expensive_call_to_get_debugging_info(), ); ``` It seems like `assert!` only evaluates the format arguments if the assertion fails, which is useful but doesn't appear to be documented anywhere. This PR documents the behavior and adds some tests. 2021-02-15 20:06:00 -06:00			`// run-pass`
Ensure debug_assert! tests get run 2021-02-16 18:05:30 -06:00			`// compile-flags: -C debug_assertions=yes`
Document that `assert!` format arguments are evaluated lazily It can be useful to do some computation in `assert!` format arguments, in order to get better error messages. For example: ```rust assert!( some_condition, "The state is invalid. Details: {}", expensive_call_to_get_debugging_info(), ); ``` It seems like `assert!` only evaluates the format arguments if the assertion fails, which is useful but doesn't appear to be documented anywhere. This PR documents the behavior and adds some tests. 2021-02-15 20:06:00 -06:00
			`#[allow(unreachable_code)]`
			`fn main() {`
			`assert!(true, "Failed: {:?}", panic!("assert! evaluated format expressions"));`
			`debug_assert!(true, "Failed: {:?}", panic!("debug_assert! evaluated format expressions"));`
			`assert_eq!(1, 1, "Failed: {:?}", panic!("assert_eq! evaluated format expressions"));`
			`debug_assert_eq!(1, 1, "Failed: {:?}", panic!("debug_assert_eq! evaluated format expressions"));`
			`assert_ne!(1, 2, "Failed: {:?}", panic!("assert_ne! evaluated format expressions"));`
			`debug_assert_ne!(1, 2, "Failed: {:?}", panic!("debug_assert_ne! evaluated format expressions"));`
			`}`