A constant item was initialized with something that is not a constant expression.
Erroneous code example:
fn create_some() -> Option<u8> {
Some(1)
}
const FOO: Option<u8> = create_some(); // error!The only functions that can be called in static or constant expressions are
const functions, and struct/enum constructors.
To fix this error, you can declare create_some as a constant function:
const fn create_some() -> Option<u8> { // declared as a const function
Some(1)
}
const FOO: Option<u8> = create_some(); // ok!
// These are also working:
struct Bar {
x: u8,
}
const OTHER_FOO: Option<u8> = Some(1);
const BAR: Bar = Bar {x: 1};