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fix(errors5): improve exercise instructions

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This commit is contained in:
Noah Cairns
2022-06-15 09:40:30 -04:00
committed by mokou
parent 582320aded
commit 5e1ca4b995
2 changed files with 20 additions and 15 deletions
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19
info.toml
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@@ -619,22 +619,17 @@ name = "errors5"
path = "exercises/error_handling/errors5.rs"
mode = "compile"
hint = """
There are two different possible `Result` types produced within
`main()`, which are propagated using `?` operators. How do we declare a
return type from `main()` that allows both?
There are two different possible `Result` types produced within `main()`, which are
propagated using `?` operators. How do we declare a return type from `main()` that allows both?
Under the hood, the `?` operator calls `From::from` on the error value to convert it to a boxed
trait object, a `Box<dyn error::Error>`. This boxed trait object is polymorphic, and since all
errors implement the `error:Error` trait, we can capture lots of different errors in one "Box"
object.
Another hint: under the hood, the `?` operator calls `From::from`
on the error value to convert it to a boxed trait object, a
`Box<dyn error::Error>`, which is polymorphic-- that means that lots of
different kinds of errors can be returned from the same function because
all errors act the same since they all implement the `error::Error` trait.
Check out this section of the book:
https://doc.rust-lang.org/book/ch09-02-recoverable-errors-with-result.html#a-shortcut-for-propagating-errors-the--operator
This exercise uses some concepts that we won't get to until later in the
course, like `Box` and the `From` trait. It's not important to understand
them in detail right now, but you can read ahead if you like.
Read more about boxing errors:
https://doc.rust-lang.org/stable/rust-by-example/error/multiple_error_types/boxing_errors.html