fix(try_from_into, from_str): hints for dyn Error

Add hints about how to return the correct type for functions that
return `Result<_, Box<dyn Error>`. Some feedback from Discord suggests
that people run into trouble with that.
This commit is contained in:
Taylor Yu 2021-05-15 14:01:17 -05:00
parent dbb2624403
commit 11d2cf0d60

View file

@ -893,7 +893,19 @@ path = "exercises/conversions/try_from_into.rs"
mode = "test" mode = "test"
hint = """ hint = """
Follow the steps provided right before the `TryFrom` implementation. Follow the steps provided right before the `TryFrom` implementation.
You can also use the example at https://doc.rust-lang.org/std/convert/trait.TryFrom.html""" You can also use the example at https://doc.rust-lang.org/std/convert/trait.TryFrom.html
You might want to look back at the exercise errorsn (or its hints) to remind
yourself about how `Box<dyn Error>` works.
If you're trying to return a string as an error, note that neither `str`
nor `String` implements `error::Error`. However, there is an implementation
of `From<&str>` for `Box<dyn Error>`. This means you can use `.into()` or
the `?` operator to convert your string into the correct error type.
If you're having trouble with using the `?` operator to convert an error string,
recall that `?` works to convert `Err(something)` into the appropriate error
type for returning from the function."""
[[exercises]] [[exercises]]
name = "as_ref_mut" name = "as_ref_mut"
@ -909,4 +921,7 @@ mode = "test"
hint = """ hint = """
The implementation of FromStr should return an Ok with a Person object, The implementation of FromStr should return an Ok with a Person object,
or an Err with an error if the string is not valid. or an Err with an error if the string is not valid.
This is almost like the `try_from_into` exercise.""" This is almost like the `try_from_into` exercise.
If you're having trouble with returning the correct error type, see the
hints for try_from_into."""