The dot operator will perform a lot of magic to convert types. It will perform
auto-referencing, auto-dereferencing, and coercion until types match.
The detailed mechanics of method lookup are defined [here](https://rustc-dev-guide.rust-lang.org/method-lookup.html),
The detailed mechanics of method lookup are defined [here][method_lookup],
but here is a brief overview that outlines the main steps.
Suppose we have a function `foo` that has a receiver (a `self`, `&self` or
@ -10,7 +10,7 @@ Suppose we have a function `foo` that has a receiver (a `self`, `&self` or
what type `Self` is before it can call the correct implementation of the function.
For this example, we will say that `value` has type `T`.
We will use [fully-qualified syntax](https://doc.rust-lang.org/nightly/book/ch19-03-advanced-traits.html#fully-qualified-syntax-for-disambiguation-calling-methods-with-the-same-name)
We will use [fully-qualified syntax][fqs]
to be more clear about exactly which type we are calling a function on.
- First, the compiler checks if we can call `T::foo(value)` directly.
@ -33,7 +33,7 @@ let first_entry = array[0];
```
How does the compiler actually compute `array[0]` when the array is behind so
many indirections? First, `array[0]` is really just syntax sugar for the [`Index`](https://doc.rust-lang.org/std/ops/trait.Index.html)
many indirections? First, `array[0]` is really just syntax sugar for the [`Index`][index]
trait - the compiler will convert `array[0]` into `array.index(0)`. Now, the
compiler checks to see if `array` implements `Index`, so that we can call the
function.
@ -90,7 +90,7 @@ impl<T> Clone for Container<T> where T: Clone {
}
```
The derived `Clone` implementation is
[only defined where `T: Clone`](https://doc.rust-lang.org/std/clone/trait.Clone.html#derivable),
[only defined where `T: Clone`][clone],
so there is no implementation for `Container<T>: Clone` for a generic `T`. The
compiler then looks to see if `&Container<T>` implements `Clone`, which it does.
So it deduces that `clone` is called by autoref, and so `bar_cloned` has type
@ -105,3 +105,8 @@ impl<T> Clone for Container<T> {
}
```
Now, the type checker deduces that `bar_cloned: Container<T>`.
thirdsgames
4 years ago