Given the Rust program:
fn main() {
let option: Option<bool> = None;
option.unwrap();
}Running the program outputs:
thread '<main>' panicked at 'called `Option::unwrap()` on a `None` value', ../src/libcore/option.rs:365
The same program using expect instead of unwrap outputs:
thread '<main>' panicked at 'oops', ../src/libcore/option.rs:333
In a program of non-trivial size, figuring out which call to unwrap or expect generated the panic is harder than it needs to be, since the line shown is where the panic actually happens inside libcore. For improved ergonomics, the file and line reported should be from the user's source code where the unwrap or expect was called.
Given the Rust program:
Running the program outputs:
The same program using
expectinstead ofunwrapoutputs:In a program of non-trivial size, figuring out which call to
unwraporexpectgenerated the panic is harder than it needs to be, since the line shown is where the panic actually happens inside libcore. For improved ergonomics, the file and line reported should be from the user's source code where theunwraporexpectwas called.