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Clarify wording

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scalexm 2018-10-21 18:30:07 +02:00 committed by Who? Me?!
parent 59eb0f085c
commit 8a533773d4
1 changed files with 11 additions and 9 deletions
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src/traits/implied-bounds.md
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@ -26,9 +26,11 @@ fn loud_insert<K>(set: &mut HashSet<K>, item: K) {
} }
``` ```
Note that in the `loud_insert` example, `HashSet<K>` is not the type of an Note that in the `loud_insert` example, `HashSet<K>` is not the type
argument of the `loud_insert` function, it only *appears* in the argument type of the `set` argument of `loud_insert`, it only *appears* in the
`&mut HashSet<K>`. argument type `&mut HashSet<K>`: we care about every type appearing
in the function's header (the header is the signature without the return type),
not only types of the function's arguments.
The rationale for applying implied bounds to input types is that, for example, The rationale for applying implied bounds to input types is that, for example,
in order to call the `loud_insert` function above, the programmer must have in order to call the `loud_insert` function above, the programmer must have
@ -52,7 +54,7 @@ arguments of their function. The same reasoning applies when using an `impl`.
Similarly, given the following trait declaration: Similarly, given the following trait declaration:
```rust,ignore ```rust,ignore
trait Copy where Self: Clone { trait Copy where Self: Clone { // desugared version of `Copy: Clone`
... ...
} }
``` ```
@ -75,11 +77,11 @@ fn fun_with_copy<T: Copy>(x: T) {
} }
``` ```
The rationale for implied bounds for traits is that if a type implements `Copy`, The rationale for implied bounds for traits is that if a type implements
that is, if there exists an `impl Copy` for that type, there *ought* to exist `Copy`, that is, if there exists an `impl Copy` for that type, there *ought*
an `impl Clone` for that type, otherwise the compiler would have reported an to exist an `impl Clone` for that type, otherwise the compiler would have
error in the first place. So again, if we were forced to repeat the additionnal reported an error in the first place. So again, if we were forced to repeat the
`where SomeType: Clone` everywhere whereas we already know that additionnal `where SomeType: Clone` everywhere whereas we already know that
`SomeType: Copy` hold, we would kind of duplicate the verification work. `SomeType: Copy` hold, we would kind of duplicate the verification work.
Implied bounds are not yet completely enforced in rustc, at the moment it only Implied bounds are not yet completely enforced in rustc, at the moment it only