1 stable release
1.0.0 | Mar 17, 2022 |
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0.1.0 |
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#1718 in Rust patterns
Used in divisibility_check
8KB
89 lines
Check
Convenience assert!
-like macros which immediately return None
or Err(...)
instead of panicking.
In a function returning an Option<T>
, invoke the macro with just enough
parameters to get a condition to check.
check!(a < n);
check_eq!(a, b);
This will expand to:
if !(a < n) {
return None;
}
if a != b {
return None;
}
In a function returning a Result<T, E>
, invoke the macro with an extra
argument, which is the error to return if the check fails (and must have type
E
), just like you can add arguments to choose a panic message with assert!
.
check!(a < n, MyError::TooBig);
check_eq!(a, b, MyError::NotEqual);
This will expand to:
if !(a < n) {
return Err(MyError::TooBig);
}
if a != b {
return Err(MyError::NotEqual);
}
lib.rs
:
Convenience assert!
-like macros which immediately returns None
or Err(...)
instead of
panicking.
Examples
In a function returning an Option<T>
, invoke the macro with just enough parameters to get a
condition to check.
check!(a < n);
check_eq!(a, b);
This will expand to:
if !(a < n) {
return None;
}
if a != b {
return None;
}
In a function returning a Result<T, E>
, invoke the macro with an extra argument, which is the
error to return if the check fails (and must have type E
), just like you can add arguments to
choose a panic message with assert!
.
check!(a < n, MyError::TooBig);
check_eq!(a, b, MyError::NotEqual);
This will expand to:
if !(a < n) {
return Err(MyError::TooBig);
}
if a != b {
return Err(MyError::NotEqual);
}
Note
Actually, the two following lines are quite equivalent:
check!(a <= b);
(a <= b).then(|| ())?;