Struct hir_ty::Adjustment

pub struct Adjustment {
    pub kind: Adjust,
    pub target: Ty,
}

Represents coercing a value to a different type of value.

We transform values by following a number of Adjust steps in order. See the documentation on variants of Adjust for more details.

Here are some common scenarios:

1. The simplest cases are where a pointer is not adjusted fat vs thin. Here the pointer will be dereferenced N times (where a dereference can happen to raw or borrowed pointers or any smart pointer which implements Deref, including Box<_>). The types of dereferences is given by autoderefs. It can then be auto-referenced zero or one times, indicated by autoref, to either a raw or borrowed pointer. In these cases unsize is false.

2. A thin-to-fat coercion involves unsizing the underlying data. We start with a thin pointer, deref a number of times, unsize the underlying data, then autoref. The ‘unsize’ phase may change a fixed length array to a dynamically sized one, a concrete object to a trait object, or statically sized struct to a dynamically sized one. E.g., &[i32; 4] -> &i32 is represented by:

   Deref(None) -> [i32; 4],
   Borrow(AutoBorrow::Ref) -> &[i32; 4],
   Unsize -> &[i32],

   Note that for a struct, the ‘deep’ unsizing of the struct is not recorded. E.g., struct Foo<T> { it: T } we can coerce &Foo<[i32; 4]> to &Foo<i32> The autoderef and -ref are the same as in the above example, but the type stored in unsize is Foo<[i32]>, we don’t store any further detail about the underlying conversions from [i32; 4] to [i32].

3. Coercing a Box<T> to Box<dyn Trait> is an interesting special case. In that case, we have the pointer we need coming in, so there are no autoderefs, and no autoref. Instead we just do the Unsize transformation. At some point, of course, Box should move out of the compiler, in which case this is analogous to transforming a struct. E.g., Box<[i32; 4]> -> Box<i32> is an Adjust::Unsize with the target Box<[i32]>.

Fields

kind: Adjust

target: Ty

Implementations

impl Adjustment

pub fn borrow(m: Mutability, ty: Ty, lt: Lifetime) -> Self

Trait Implementations

impl Clone for Adjustment

fn clone(&self) -> Adjustment

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Adjustment

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Hash for Adjustment

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl PartialEq for Adjustment

fn eq(&self, other: &Adjustment) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Eq for Adjustment

impl StructuralPartialEq for Adjustment