Enum rustc_middle::mir::ProjectionElem
source · pub enum ProjectionElem<V, T> {
Deref,
Field(FieldIdx, T),
Index(V),
ConstantIndex {
offset: u64,
min_length: u64,
from_end: bool,
},
Subslice {
from: u64,
to: u64,
from_end: bool,
},
Downcast(Option<Symbol>, VariantIdx),
OpaqueCast(T),
Subtype(T),
}
Variants§
Deref
Field(FieldIdx, T)
A field (e.g., f
in _1.f
) is one variant of ProjectionElem
. Conceptually,
rustc can identify that a field projection refers to either two different regions of memory
or the same one between the base and the ‘projection element’.
Read more about projections in the rustc-dev-guide
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
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
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(T)
Like an explicit cast from an opaque type to a concrete type, but without requiring an intermediate variable.
Subtype(T)
A Subtype(T)
projection is applied to any StatementKind::Assign
where
type of lvalue doesn’t match the type of rvalue, the primary goal is making subtyping
explicit during optimizations and codegen.
This projection doesn’t impact the runtime behavior of the program except for potentially changing some type metadata of the interpreter or codegen backend.
This goal is achieved with mir_transform pass Subtyper
, which runs right after
borrowchecker, as we only care about subtyping that can affect trait selection and
TypeId
.
Implementations§
source§impl<V, T> ProjectionElem<V, T>
impl<V, T> ProjectionElem<V, T>
sourcefn is_indirect(&self) -> bool
fn is_indirect(&self) -> bool
Returns true
if the target of this projection may refer to a different region of memory
than the base.
sourcepub fn is_stable_offset(&self) -> bool
pub fn is_stable_offset(&self) -> bool
Returns true
if the target of this projection always refers to the same memory region
whatever the state of the program.
sourcepub fn is_downcast_to(&self, v: VariantIdx) -> bool
pub fn is_downcast_to(&self, v: VariantIdx) -> bool
Returns true
if this is a Downcast
projection with the given VariantIdx
.
sourcepub fn is_field_to(&self, f: FieldIdx) -> bool
pub fn is_field_to(&self, f: FieldIdx) -> bool
Returns true
if this is a Field
projection with the given index.
sourcepub fn can_use_in_debuginfo(&self) -> bool
pub fn can_use_in_debuginfo(&self) -> bool
Returns true
if this is accepted inside VarDebugInfoContents::Place
.
Trait Implementations§
source§impl<V: Clone, T: Clone> Clone for ProjectionElem<V, T>
impl<V: Clone, T: Clone> Clone for ProjectionElem<V, T>
source§fn clone(&self) -> ProjectionElem<V, T>
fn clone(&self) -> ProjectionElem<V, T>
1.0.0 · source§fn clone_from(&mut self, source: &Self)
fn clone_from(&mut self, source: &Self)
source
. Read moresource§impl<'tcx, V, T, __D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<__D> for ProjectionElem<V, T>where
T: Decodable<__D>,
V: Decodable<__D>,
impl<'tcx, V, T, __D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<__D> for ProjectionElem<V, T>where T: Decodable<__D>, V: Decodable<__D>,
source§impl<'tcx, V, T, __E: TyEncoder<I = TyCtxt<'tcx>>> Encodable<__E> for ProjectionElem<V, T>where
T: Encodable<__E>,
V: Encodable<__E>,
impl<'tcx, V, T, __E: TyEncoder<I = TyCtxt<'tcx>>> Encodable<__E> for ProjectionElem<V, T>where T: Encodable<__E>, V: Encodable<__E>,
source§impl<'__ctx, V, T> HashStable<StableHashingContext<'__ctx>> for ProjectionElem<V, T>where
T: HashStable<StableHashingContext<'__ctx>>,
V: HashStable<StableHashingContext<'__ctx>>,
impl<'__ctx, V, T> HashStable<StableHashingContext<'__ctx>> for ProjectionElem<V, T>where T: HashStable<StableHashingContext<'__ctx>>, V: HashStable<StableHashingContext<'__ctx>>,
fn hash_stable( &self, __hcx: &mut StableHashingContext<'__ctx>, __hasher: &mut StableHasher )
source§impl<V: Ord, T: Ord> Ord for ProjectionElem<V, T>
impl<V: Ord, T: Ord> Ord for ProjectionElem<V, T>
source§fn cmp(&self, other: &ProjectionElem<V, T>) -> Ordering
fn cmp(&self, other: &ProjectionElem<V, T>) -> Ordering
1.21.0 · source§fn max(self, other: Self) -> Selfwhere
Self: Sized,
fn max(self, other: Self) -> Selfwhere Self: Sized,
source§impl<V: PartialEq, T: PartialEq> PartialEq<ProjectionElem<V, T>> for ProjectionElem<V, T>
impl<V: PartialEq, T: PartialEq> PartialEq<ProjectionElem<V, T>> for ProjectionElem<V, T>
source§fn eq(&self, other: &ProjectionElem<V, T>) -> bool
fn eq(&self, other: &ProjectionElem<V, T>) -> bool
self
and other
values to be equal, and is used
by ==
.source§impl<V: PartialOrd, T: PartialOrd> PartialOrd<ProjectionElem<V, T>> for ProjectionElem<V, T>
impl<V: PartialOrd, T: PartialOrd> PartialOrd<ProjectionElem<V, T>> for ProjectionElem<V, T>
source§fn partial_cmp(&self, other: &ProjectionElem<V, T>) -> Option<Ordering>
fn partial_cmp(&self, other: &ProjectionElem<V, T>) -> Option<Ordering>
1.0.0 · source§fn le(&self, other: &Rhs) -> bool
fn le(&self, other: &Rhs) -> bool
self
and other
) and is used by the <=
operator. Read moresource§impl<'tcx, V, T> TypeFoldable<TyCtxt<'tcx>> for ProjectionElem<V, T>where
T: TypeFoldable<TyCtxt<'tcx>>,
V: TypeFoldable<TyCtxt<'tcx>>,
impl<'tcx, V, T> TypeFoldable<TyCtxt<'tcx>> for ProjectionElem<V, T>where T: TypeFoldable<TyCtxt<'tcx>>, V: TypeFoldable<TyCtxt<'tcx>>,
source§fn try_fold_with<__F: FallibleTypeFolder<TyCtxt<'tcx>>>(
self,
__folder: &mut __F
) -> Result<Self, __F::Error>
fn try_fold_with<__F: FallibleTypeFolder<TyCtxt<'tcx>>>( self, __folder: &mut __F ) -> Result<Self, __F::Error>
source§fn fold_with<F>(self, folder: &mut F) -> Selfwhere
F: TypeFolder<I>,
fn fold_with<F>(self, folder: &mut F) -> Selfwhere F: TypeFolder<I>,
try_fold_with
for use with infallible
folders. Do not override this method, to ensure coherence with
try_fold_with
.source§impl<'tcx, V, T> TypeVisitable<TyCtxt<'tcx>> for ProjectionElem<V, T>where
T: TypeVisitable<TyCtxt<'tcx>>,
V: TypeVisitable<TyCtxt<'tcx>>,
impl<'tcx, V, T> TypeVisitable<TyCtxt<'tcx>> for ProjectionElem<V, T>where T: TypeVisitable<TyCtxt<'tcx>>, V: TypeVisitable<TyCtxt<'tcx>>,
source§fn visit_with<__V: TypeVisitor<TyCtxt<'tcx>>>(
&self,
__visitor: &mut __V
) -> ControlFlow<__V::BreakTy>
fn visit_with<__V: TypeVisitor<TyCtxt<'tcx>>>( &self, __visitor: &mut __V ) -> ControlFlow<__V::BreakTy>
impl<V: Copy, T: Copy> Copy for ProjectionElem<V, T>
impl<V: Eq, T: Eq> Eq for ProjectionElem<V, T>
impl<V, T> StructuralEq for ProjectionElem<V, T>
impl<V, T> StructuralPartialEq for ProjectionElem<V, T>
Auto Trait Implementations§
impl<V, T> RefUnwindSafe for ProjectionElem<V, T>where T: RefUnwindSafe, V: RefUnwindSafe,
impl<V, T> Send for ProjectionElem<V, T>where T: Send, V: Send,
impl<V, T> Sync for ProjectionElem<V, T>where T: Sync, V: Sync,
impl<V, T> Unpin for ProjectionElem<V, T>where T: Unpin, V: Unpin,
impl<V, T> UnwindSafe for ProjectionElem<V, T>where T: UnwindSafe, V: UnwindSafe,
Blanket Implementations§
source§impl<'tcx, T> ArenaAllocatable<'tcx, IsCopy> for Twhere
T: Copy,
impl<'tcx, T> ArenaAllocatable<'tcx, IsCopy> for Twhere T: Copy,
fn allocate_on<'a>(self, arena: &'a Arena<'tcx>) -> &'a mut T
fn allocate_from_iter<'a>( arena: &'a Arena<'tcx>, iter: impl IntoIterator<Item = T> ) -> &'a mut [T]
source§impl<T> BorrowMut<T> for Twhere
T: ?Sized,
impl<T> BorrowMut<T> for Twhere T: ?Sized,
source§fn borrow_mut(&mut self) -> &mut T
fn borrow_mut(&mut self) -> &mut T
source§impl<T, R> CollectAndApply<T, R> for T
impl<T, R> CollectAndApply<T, R> for T
source§impl<Tcx, T> DepNodeParams<Tcx> for Twhere
Tcx: DepContext,
T: for<'a> HashStable<StableHashingContext<'a>> + Debug,
impl<Tcx, T> DepNodeParams<Tcx> for Twhere Tcx: DepContext, T: for<'a> HashStable<StableHashingContext<'a>> + Debug,
default fn fingerprint_style() -> FingerprintStyle
source§default fn to_fingerprint(&self, tcx: Tcx) -> Fingerprint
default fn to_fingerprint(&self, tcx: Tcx) -> Fingerprint
default fn to_debug_str(&self, _: Tcx) -> String
source§default fn recover(_: Tcx, _: &DepNode) -> Option<T>
default fn recover(_: Tcx, _: &DepNode) -> Option<T>
DepNode
,
something which is needed when forcing DepNode
s during red-green
evaluation. The query system will only call this method if
fingerprint_style()
is not FingerprintStyle::Opaque
.
It is always valid to return None
here, in which case incremental
compilation will treat the query as having changed instead of forcing it.source§impl<P> IntoQueryParam<P> for P
impl<P> IntoQueryParam<P> for P
fn into_query_param(self) -> P
source§impl<'tcx, T> IsSuggestable<'tcx> for Twhere
T: TypeVisitable<TyCtxt<'tcx>> + TypeFoldable<TyCtxt<'tcx>>,
impl<'tcx, T> IsSuggestable<'tcx> for Twhere T: TypeVisitable<TyCtxt<'tcx>> + TypeFoldable<TyCtxt<'tcx>>,
source§impl<T> MaybeResult<T> for T
impl<T> MaybeResult<T> for T
source§impl<'tcx, T> ToPredicate<'tcx, T> for T
impl<'tcx, T> ToPredicate<'tcx, T> for T
fn to_predicate(self, _tcx: TyCtxt<'tcx>) -> T
source§impl<'tcx, T> TypeVisitableExt<'tcx> for Twhere
T: TypeVisitable<TyCtxt<'tcx>>,
impl<'tcx, T> TypeVisitableExt<'tcx> for Twhere T: TypeVisitable<TyCtxt<'tcx>>,
source§fn has_vars_bound_at_or_above(&self, binder: DebruijnIndex) -> bool
fn has_vars_bound_at_or_above(&self, binder: DebruijnIndex) -> bool
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.source§fn has_vars_bound_above(&self, binder: DebruijnIndex) -> bool
fn has_vars_bound_above(&self, binder: DebruijnIndex) -> bool
true
if this type has any regions that escape binder
(and
hence are not bound by it).source§fn has_escaping_bound_vars(&self) -> bool
fn has_escaping_bound_vars(&self) -> bool
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. Read morefn has_type_flags(&self, flags: TypeFlags) -> bool
fn has_projections(&self) -> bool
fn has_inherent_projections(&self) -> bool
fn has_opaque_types(&self) -> bool
fn has_generators(&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 has_infer(&self) -> bool
fn has_placeholders(&self) -> bool
fn has_non_region_placeholders(&self) -> bool
fn has_param(&self) -> bool
source§fn has_free_regions(&self) -> bool
fn has_free_regions(&self) -> bool
fn has_erased_regions(&self) -> bool
source§fn has_erasable_regions(&self) -> bool
fn has_erasable_regions(&self) -> bool
source§fn is_global(&self) -> bool
fn is_global(&self) -> bool
source§fn has_late_bound_regions(&self) -> bool
fn has_late_bound_regions(&self) -> bool
source§fn has_non_region_late_bound(&self) -> bool
fn has_non_region_late_bound(&self) -> bool
source§fn has_late_bound_vars(&self) -> bool
fn has_late_bound_vars(&self) -> bool
source§fn still_further_specializable(&self) -> bool
fn still_further_specializable(&self) -> bool
impl
specialization.source§impl<Tcx, T> Value<Tcx> for Twhere
Tcx: DepContext,
impl<Tcx, T> Value<Tcx> for Twhere Tcx: DepContext,
default fn from_cycle_error( tcx: Tcx, cycle: &[QueryInfo], _guar: ErrorGuaranteed ) -> T
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.