Comparing DateTime<Local> with DateTime<Utc> compiles, but should not #1739
Description
The following code compiles and runs:
use chrono;
fn main() {
let l = chrono::Local::now();
let u = chrono::Utc::now();
dbg!(l == u);
}
Currently, this works and performs an implicit conversion(or even worse), but I believe it should not be allowed.
May be this?
impl<Tz: TimeZone, Tz2: TimeZone> PartialOrd<DateTime<Tz2>> for DateTime<Tz> {
/// Compare two DateTimes based on their true time, ignoring time zones
Why this is a problem:
It hides implicit conversions between time zones
Makes it too easy to compare DateTime values from different zones without being explicit
Can lead to subtle bugs when developers accidentally mix local and UTC times
Expected behavior:
The code above should fail to compile, requiring explicit conversion (e.g. l.with_timezone(&Utc) or u.with_timezone(&Local)) before comparison.
Proposal:
Disallow PartialEq, PartialOrd, etc. between DateTime and DateTime when Tz1 != Tz2.