fix: use trait objects for try_from_into
Use `Box<dyn error::Error>` to allow solutions to use `?` to propagate
errors.  In the tests, explicitly check `is_ok()` instead of trying to
force the error type to `String` (or other `PartialEq` type) using
`assert_eq!()`.
// instead of the target type itself.
// You can read more about it at https://doc.rust-lang.org/std/convert/trait.TryFrom.html
use std::convert::{TryFrom, TryInto};
+use std::error;
#[derive(Debug, PartialEq)]
struct Color {
@@ -24,19 +25,19 @@ struct Color {
// Tuple implementation
impl TryFrom<(i16, i16, i16)> for Color {
- type Error = String;
+ type Error = Box<dyn error::Error>;
fn try_from(tuple: (i16, i16, i16)) -> Result<Self, Self::Error> {}
}
// Array implementation
impl TryFrom<[i16; 3]> for Color {
- type Error = String;
+ type Error = Box<dyn error::Error>;
fn try_from(arr: [i16; 3]) -> Result<Self, Self::Error> {}
}
// Slice implementation
impl TryFrom<&[i16]> for Color {
- type Error = String;
+ type Error = Box<dyn error::Error>;
fn try_from(slice: &[i16]) -> Result<Self, Self::Error> {}
}
@@ -76,41 +77,43 @@ mod tests {
}
#[test]
fn test_tuple_correct() {
- let c: Result<Color, String> = (183, 65, 14).try_into();
+ let c: Result<Color, _> = (183, 65, 14).try_into();
+ assert!(c.is_ok());
assert_eq!(
- c,
- Ok(Color {
+ c.unwrap(),
+ Color {
red: 183,
green: 65,
blue: 14
- })
+ }
);
}
#[test]
fn test_array_out_of_range_positive() {
- let c: Result<Color, String> = [1000, 10000, 256].try_into();
+ let c: Result<Color, _> = [1000, 10000, 256].try_into();
assert!(c.is_err());
}
#[test]
fn test_array_out_of_range_negative() {
- let c: Result<Color, String> = [-10, -256, -1].try_into();
+ let c: Result<Color, _> = [-10, -256, -1].try_into();
assert!(c.is_err());
}
#[test]
fn test_array_sum() {
- let c: Result<Color, String> = [-1, 255, 255].try_into();
+ let c: Result<Color, _> = [-1, 255, 255].try_into();
assert!(c.is_err());
}
#[test]
fn test_array_correct() {
- let c: Result<Color, String> = [183, 65, 14].try_into();
+ let c: Result<Color, _> = [183, 65, 14].try_into();
+ assert!(c.is_ok());
assert_eq!(
- c,
- Ok(Color {
+ c.unwrap(),
+ Color {
red: 183,
green: 65,
blue: 14
- })
+ }
);
}
#[test]
@@ -131,14 +134,15 @@ mod tests {
#[test]
fn test_slice_correct() {
let v = vec![183, 65, 14];
- let c: Result<Color, String> = Color::try_from(&v[..]);
+ let c: Result<Color, _> = Color::try_from(&v[..]);
+ assert!(c.is_ok());
assert_eq!(
- c,
- Ok(Color {
+ c.unwrap(),
+ Color {
red: 183,
green: 65,
blue: 14
- })
+ }
);
}
#[test]
