Enum rustc_middle::mir::ProjectionElem

pub enum ProjectionElem<V, T1, T2> {
    Deref,
    Field(Field, T1),
    Index(V),
    ConstantIndex {
        offset: u64,
        min_length: u64,
        from_end: bool,
    },
    Subslice {
        from: u64,
        to: u64,
        from_end: bool,
    },
    Downcast(Option<Symbol>, VariantIdx),
    OpaqueCast(T2),
}

The different kinds of projections that can be used in the projection of a Place.

T1 is the generic type for a field projection. For an actual projection on a Place this parameter will always be Ty, but the field type can be unavailable when building (by using PlaceBuilder) places that correspond to upvars. T2 is the generic type for an OpaqueCast (is generic since it’s abstracted over in dataflow analysis, see AbstractElem).

Variants

Deref

Field(Field, T1)

Index(V)

Index into a slice/array.

Note that this does not also dereference, and so it does not exactly correspond to slice indexing in Rust. In other words, in the below Rust code:

let x = &[1, 2, 3, 4];
let i = 2;
x[i];

The x[i] is turned into a Deref followed by an Index, not just an Index. The same thing is true of the ConstantIndex and Subslice projections below.

ConstantIndex

Fields

offset: u64

index or -index (in Python terms), depending on from_end

min_length: u64

The thing being indexed must be at least this long. For arrays this is always the exact length.

from_end: bool

Counting backwards from end? This is always false when indexing an array.

These indices are generated by slice patterns. Easiest to explain by example:

[X, _, .._, _, _] => { offset: 0, min_length: 4, from_end: false },
[_, X, .._, _, _] => { offset: 1, min_length: 4, from_end: false },
[_, _, .._, X, _] => { offset: 2, min_length: 4, from_end: true },
[_, _, .._, _, X] => { offset: 1, min_length: 4, from_end: true },

Subslice

Fields

from: u64

to: u64

from_end: bool

Whether to counts from the start or end of the array/slice. For PlaceElems this is true if and only if the base is a slice. For ProjectionKind, this can also be true for arrays.

These indices are generated by slice patterns.

If from_end is true slice[from..slice.len() - to]. Otherwise array[from..to].

Downcast(Option<Symbol>, VariantIdx)

“Downcast” to a variant of an enum or a generator.

The included Symbol is the name of the variant, used for printing MIR.

OpaqueCast(T2)

Like an explicit cast from an opaque type to a concrete type, but without requiring an intermediate variable.

Implementations

impl<V, T, U> ProjectionElem<V, T, U>

fn is_indirect(&self) -> bool

Returns true if the target of this projection may refer to a different region of memory than the base.

pub fn is_downcast_to(&self, v: VariantIdx) -> bool

Returns true if this is a Downcast projection with the given VariantIdx.

pub fn is_field_to(&self, f: Field) -> bool

Returns true if this is a Field projection with the given index.

Trait Implementations

impl<V: Clone, T1: Clone, T2: Clone> Clone for ProjectionElem<V, T1, T2>

fn clone(&self) -> ProjectionElem<V, T1, T2>

Returns a copy of the value.

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

Performs copy-assignment from source.

impl<V: Debug, T1: Debug, T2: Debug> Debug for ProjectionElem<V, T1, T2>

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

Formats the value using the given formatter.

impl<'tcx, V, T1, T2, __D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<__D> for ProjectionElem<V, T1, T2>where
    T1: Decodable<__D>,
    V: Decodable<__D>,
    T2: Decodable<__D>,

fn decode(__decoder: &mut __D) -> Self

impl<'tcx, V, T1, T2, __E: TyEncoder<I = TyCtxt<'tcx>>> Encodable<__E> for ProjectionElem<V, T1, T2>where
    T1: Encodable<__E>,
    V: Encodable<__E>,
    T2: Encodable<__E>,

fn encode(&self, __encoder: &mut __E)

impl<'tcx> From<ProjectionElem<Local, Ty<'tcx>, Ty<'tcx>>> for UpvarProjectionElem<'tcx>

fn from(elem: PlaceElem<'tcx>) -> Self

Converts to this type from the input type.

impl<V: Hash, T1: Hash, T2: Hash> Hash for ProjectionElem<V, T1, T2>

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<'__ctx, V, T1, T2> HashStable<StableHashingContext<'__ctx>> for ProjectionElem<V, T1, T2>where
    T1: HashStable<StableHashingContext<'__ctx>>,
    V: HashStable<StableHashingContext<'__ctx>>,
    T2: HashStable<StableHashingContext<'__ctx>>,

fn hash_stable(
    &self,
    __hcx: &mut StableHashingContext<'__ctx>,
    __hasher: &mut StableHasher
)

impl<V: Ord, T1: Ord, T2: Ord> Ord for ProjectionElem<V, T1, T2>

fn cmp(&self, other: &ProjectionElem<V, T1, T2>) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Selfwhere
    Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Selfwhere
    Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Selfwhere
    Self: Sized + PartialOrd<Self>,

Restrict a value to a certain interval.

impl<V: PartialEq, T1: PartialEq, T2: PartialEq> PartialEq<ProjectionElem<V, T1, T2>> for ProjectionElem<V, T1, T2>

fn eq(&self, other: &ProjectionElem<V, T1, T2>) -> bool

This method tests for self and other values to be equal, and is used by ==.

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

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

impl<V: PartialOrd, T1: PartialOrd, T2: PartialOrd> PartialOrd<ProjectionElem<V, T1, T2>> for ProjectionElem<V, T1, T2>

fn partial_cmp(&self, other: &ProjectionElem<V, T1, T2>) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

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

This method tests less than (for self and other) and is used by the < operator.

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

This method tests less than or equal to (for self and other) and is used by the <= operator.

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

This method tests greater than (for self and other) and is used by the > operator.

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

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl<'tcx, V, T1, T2> TypeFoldable<'tcx> for ProjectionElem<V, T1, T2>where
    T1: TypeFoldable<'tcx>,
    V: TypeFoldable<'tcx>,
    T2: TypeFoldable<'tcx>,

fn try_fold_with<__F: FallibleTypeFolder<'tcx>>(
    self,
    __folder: &mut __F
) -> Result<Self, __F::Error>

The entry point for folding. To fold a value t with a folder f call: t.try_fold_with(f).

fn fold_with<F: TypeFolder<'tcx>>(self, folder: &mut F) -> Self

A convenient alternative to try_fold_with for use with infallible folders. Do not override this method, to ensure coherence with try_fold_with.

impl<'tcx, V, T1, T2> TypeVisitable<'tcx> for ProjectionElem<V, T1, T2>where
    T1: TypeVisitable<'tcx>,
    V: TypeVisitable<'tcx>,
    T2: TypeVisitable<'tcx>,

fn visit_with<__V: TypeVisitor<'tcx>>(
    &self,
    __visitor: &mut __V
) -> ControlFlow<__V::BreakTy>

The entry point for visiting. To visit a value t with a visitor v call: t.visit_with(v).

fn has_vars_bound_at_or_above(&self, binder: DebruijnIndex) -> bool

Returns true if self has any late-bound regions that are either bound by binder or bound by some binder outside of binder. If binder is ty::INNERMOST, this indicates whether there are any late-bound regions that appear free.

fn has_vars_bound_above(&self, binder: DebruijnIndex) -> bool

Returns true if this type has any regions that escape binder (and hence are not bound by it).

fn has_escaping_bound_vars(&self) -> bool

Return true if this type has regions that are not a part of the type. For example, for<'a> fn(&'a i32) return false, while fn(&'a i32) would return true. The latter can occur when traversing through the former.

fn has_type_flags(&self, flags: TypeFlags) -> bool

fn has_projections(&self) -> bool

fn has_opaque_types(&self) -> bool

fn references_error(&self) -> bool

fn error_reported(&self) -> Result<(), ErrorGuaranteed>

fn has_non_region_param(&self) -> bool

fn has_infer_regions(&self) -> bool

fn has_infer_types(&self) -> bool

fn has_non_region_infer(&self) -> bool

fn needs_infer(&self) -> bool

fn has_placeholders(&self) -> bool

fn needs_subst(&self) -> bool

fn has_free_regions(&self) -> bool

“Free” regions in this context means that it has any region that is not (a) erased or (b) late-bound.

fn has_erased_regions(&self) -> bool

fn has_erasable_regions(&self) -> bool

True if there are any un-erased free regions.

fn is_global(&self) -> bool

Indicates whether this value references only ‘global’ generic parameters that are the same regardless of what fn we are in. This is used for caching.

fn has_late_bound_regions(&self) -> bool

True if there are any late-bound regions

fn still_further_specializable(&self) -> bool

Indicates whether this value still has parameters/placeholders/inference variables which could be replaced later, in a way that would change the results of impl specialization.

impl<V: Copy, T1: Copy, T2: Copy> Copy for ProjectionElem<V, T1, T2>

impl<V: Eq, T1: Eq, T2: Eq> Eq for ProjectionElem<V, T1, T2>

impl<V, T1, T2> StructuralEq for ProjectionElem<V, T1, T2>

impl<V, T1, T2> StructuralPartialEq for ProjectionElem<V, T1, T2>

Layout

Note: Unable to compute type layout, possibly due to this type having generic parameters. Layout can only be computed for concrete, fully-instantiated types.