formatting
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@ -96,7 +96,11 @@ impl LateLintPass<'_> for CheckTokioAsyncReadExtTrait {
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## Creating traits programmatically
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## Creating traits programmatically
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Traits are often generic over a type e.g. `Borrow<T>` is generic over `T`, and rust allows us to implement a trait for a specific type. For example, we can implement `Borrow<str>` for a hypothetical type `Foo`. Let's suppose that we would like to find whether our type actually implements `Borrow<[u8]>`. To do so, we need to supply a type that represents `[u8]`, but `[u8]` is also a generic, it's a slice over `u8`. We can create this type using Ty::new_slice method. The following code demonstrates how to do this:
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Traits are often generic over a type e.g. `Borrow<T>` is generic over `T`, and rust allows us to implement a trait for
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a specific type. For example, we can implement `Borrow<str>` for a hypothetical type `Foo`. Let's suppose that we
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would like to find whether our type actually implements `Borrow<[u8]>`. To do so, we need to supply a type that
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represents `[u8]`, but `[u8]` is also a generic, it's a slice over `u8`. We can create this type using Ty::new_slice
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method. The following code demonstrates how to do this:
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```rust
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```rust
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@ -111,7 +115,9 @@ if implements_trait(cx, ty, borrow_id, &[Ty::new_slice(cx.tcx, cx.tcx.types.u8).
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}
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}
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```
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```
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Here, we use `Ty::new_slice` to create a type that represents `[T]` and supply `u8` as a type parameter, and then we go on normally with `implements_trait` function. The [Ty] struct allows us to create types programmatically, and it's useful when we need to create types that we can't obtain through the usual means.
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Here, we use `Ty::new_slice` to create a type that represents `[T]` and supply `u8` as a type parameter, and then we go
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on normally with `implements_trait` function. The [Ty] struct allows us to create types programmatically, and it's
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useful when we need to create types that we can't obtain through the usual means.
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@ -125,11 +125,15 @@ the [`TypeckResults::node_type()`][node_type] method inside of bodies.
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## Creating Types programmatically
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## Creating Types programmatically
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A common usecase for creating types programmatically is when we want to check if a type implements a trait. We have a section on this in the [Trait Checking](trait_checking.md) chapter, but given the importance of this topic, we will also cover it here.
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A common usecase for creating types programmatically is when we want to check if a type implements a trait. We have
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a section on this in the [Trait Checking](trait_checking.md) chapter, but given the importance of this topic, we will
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also cover it a bit here.
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When we refer to "type" in this context, we refer to `ty::Ty`. To create a `ty::Ty` programmatically, we rely on `Ty::new_*` methods. These methods create a `TyKind` and then wrap it in a `Ty` struct.
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When we refer to "type" in this context, we refer to `ty::Ty`. To create a `ty::Ty` programmatically, we rely on
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`Ty::new_*` methods. These methods create a `TyKind` and then wrap it in a `Ty` struct.
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This means we have access to all the primitive types, such as `Ty::new_char`, `Ty::new_bool`, `Ty::new_int`, etc. We can also create more complex types, such as slices, tuples, and references.
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This means we have access to all the primitive types, such as `Ty::new_char`, `Ty::new_bool`, `Ty::new_int`, etc.
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We can also create more complex types, such as slices, tuples, and references.
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Here's an example of how to create a `Ty` for a slice of `u8`, i.e. `[u8]`
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Here's an example of how to create a `Ty` for a slice of `u8`, i.e. `[u8]`
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