Duration overflows when created with Duration::new(u64::MAX, u32::MAX)

[brson]

Creating Duration::new(u64::MAX, u32::MAX) results in a duration of 3 seconds.

From the documentation, it's not clear what Duration::new is supposed to do on overflow, but right now it silently wraps, whereas its overloaded math operators used explicit checked math.

Playground link.

I thought that compiling this in debug mode would panic because of overflow but it doesn't.

[brson]

Relatedly, I couldn't figure out how to create a maximum-sized Duration.

[japaric]

Relatedly, I couldn't figure out how to create a maximum-sized Duration.

Duration::new(u64::MAX, NANOS_PER_SEC - 1) (where NANOS_PER_SEC = 1_000_000_000) returns the maximum duration. Perhaps we could add a Duration::max() constructor or a time::MAX_DURATION constant to make it more obvious.

[sfackler]

Could be Duration::max_value() to match primitive numeric types.

[nodakai]

• https://play.rust-lang.org/?gist=af78de22865a57f7a27c&version=nightly

#![crate_type="lib"]
pub fn new() -> u32 {
    std::u32::MAX + 10
}

↓

ret i32 9

So constant folding doesn't honor the checked arithmetic semantics?

On the other hand, a const item raises a compile error only when the value is referenced by a function:

• https://play.rust-lang.org/?gist=7bf14b39e8fd488c46fc&version=nightly

#![crate_type="lib"]

pub const X: u32 = std::u32::MAX + 10;

// pub fn new() -> u32 { X }

[alexcrichton]

This has since been fixed, so closing.