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),
}

Variants§

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Deref

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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

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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.

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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 },
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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].

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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.

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OpaqueCast(T)

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

Implementations§

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

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fn is_indirect(&self) -> bool

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

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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.

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

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

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

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

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pub fn can_use_in_debuginfo(&self) -> bool

Returns true if this is accepted inside VarDebugInfoContents::Place.

Trait Implementations§

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impl<V: Clone, T: Clone> Clone for ProjectionElem<V, T>

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

Returns a copy of the value. Read more
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fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source. Read more
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impl<V: Debug, T: Debug> Debug for ProjectionElem<V, T>

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

Formats the value using the given formatter. Read more
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impl<'tcx, V, T, __D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<__D> for ProjectionElem<V, T>where T: Decodable<__D>, V: Decodable<__D>,

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

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impl<'tcx, V, T, __E: TyEncoder<I = TyCtxt<'tcx>>> Encodable<__E> for ProjectionElem<V, T>where T: Encodable<__E>, V: Encodable<__E>,

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

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impl<V: Hash, T: Hash> Hash for ProjectionElem<V, T>

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

Feeds this value into the given Hasher. Read more
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fn hash_slice<H>(data: &[Self], state: &mut H)where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher. Read more
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impl<'__ctx, V, T> HashStable<StableHashingContext<'__ctx>> for ProjectionElem<V, T>where T: HashStable<StableHashingContext<'__ctx>>, V: HashStable<StableHashingContext<'__ctx>>,

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

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impl<V: Ord, T: Ord> Ord for ProjectionElem<V, T>

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

This method returns an Ordering between self and other. Read more
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fn max(self, other: Self) -> Selfwhere Self: Sized,

Compares and returns the maximum of two values. Read more
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fn min(self, other: Self) -> Selfwhere Self: Sized,

Compares and returns the minimum of two values. Read more
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fn clamp(self, min: Self, max: Self) -> Selfwhere Self: Sized + PartialOrd<Self>,

Restrict a value to a certain interval. Read more
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impl<V: PartialEq, T: PartialEq> PartialEq<ProjectionElem<V, T>> for ProjectionElem<V, T>

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

This method tests for self and other values to be equal, and is used by ==.
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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.
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impl<V: PartialOrd, T: PartialOrd> PartialOrd<ProjectionElem<V, T>> for ProjectionElem<V, T>

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

This method returns an ordering between self and other values if one exists. Read more
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fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator. Read more
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fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator. Read more
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fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator. Read more
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fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator. Read more
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impl<'tcx, V, T> TypeFoldable<TyCtxt<'tcx>> for ProjectionElem<V, T>where T: TypeFoldable<TyCtxt<'tcx>>, V: TypeFoldable<TyCtxt<'tcx>>,

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fn try_fold_with<__F: FallibleTypeFolder<TyCtxt<'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). Read more
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fn fold_with<F>(self, folder: &mut F) -> Selfwhere F: TypeFolder<I>,

A convenient alternative to try_fold_with for use with infallible folders. Do not override this method, to ensure coherence with try_fold_with.
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impl<'tcx, V, T> TypeVisitable<TyCtxt<'tcx>> for ProjectionElem<V, T>where T: TypeVisitable<TyCtxt<'tcx>>, V: TypeVisitable<TyCtxt<'tcx>>,

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fn visit_with<__V: TypeVisitor<TyCtxt<'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). Read more
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impl<V: Copy, T: Copy> Copy for ProjectionElem<V, T>

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impl<V: Eq, T: Eq> Eq for ProjectionElem<V, T>

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impl<V, T> StructuralEq for ProjectionElem<V, T>

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impl<V, T> StructuralPartialEq for ProjectionElem<V, T>

Auto Trait Implementations§

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impl<V, T> RefUnwindSafe for ProjectionElem<V, T>where T: RefUnwindSafe, V: RefUnwindSafe,

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impl<V, T> Send for ProjectionElem<V, T>where T: Send, V: Send,

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impl<V, T> Sync for ProjectionElem<V, T>where T: Sync, V: Sync,

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impl<V, T> Unpin for ProjectionElem<V, T>where T: Unpin, V: Unpin,

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impl<V, T> UnwindSafe for ProjectionElem<V, T>where T: UnwindSafe, V: UnwindSafe,

Blanket Implementations§

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impl<T> Aligned for T

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const ALIGN: Alignment = _

Alignment of Self.
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impl<T> Any for Twhere T: 'static + ?Sized,

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fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
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impl<'tcx, T> ArenaAllocatable<'tcx, IsCopy> for Twhere T: Copy,

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fn allocate_on<'a>(self, arena: &'a Arena<'tcx>) -> &'a mut T

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fn allocate_from_iter<'a>( arena: &'a Arena<'tcx>, iter: impl IntoIterator<Item = T> ) -> &'a mut [T]

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impl<T> Borrow<T> for Twhere T: ?Sized,

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fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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impl<T> BorrowMut<T> for Twhere T: ?Sized,

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fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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impl<T, R> CollectAndApply<T, R> for T

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fn collect_and_apply<I, F>(iter: I, f: F) -> Rwhere I: Iterator<Item = T>, F: FnOnce(&[T]) -> R,

Equivalent to f(&iter.collect::<Vec<_>>()).

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type Output = R

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impl<Tcx, T> DepNodeParams<Tcx> for Twhere Tcx: DepContext, T: for<'a> HashStable<StableHashingContext<'a>> + Debug,

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default fn fingerprint_style() -> FingerprintStyle

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default fn to_fingerprint(&self, tcx: Tcx) -> Fingerprint

This method turns the parameters of a DepNodeConstructor into an opaque Fingerprint to be used in DepNode. Not all DepNodeParams support being turned into a Fingerprint (they don’t need to if the corresponding DepNode is anonymous).
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default fn to_debug_str(&self, _: Tcx) -> String

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default fn recover(_: Tcx, _: &DepNode) -> Option<T>

This method tries to recover the query key from the given DepNode, something which is needed when forcing DepNodes 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.
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impl<T> From<T> for T

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fn from(t: T) -> T

Returns the argument unchanged.

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impl<T, U> Into<U> for Twhere U: From<T>,

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fn into(self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

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impl<P> IntoQueryParam<P> for P

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impl<'tcx, T> IsSuggestable<'tcx> for Twhere T: TypeVisitable<TyCtxt<'tcx>> + TypeFoldable<TyCtxt<'tcx>>,

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fn is_suggestable(self, tcx: TyCtxt<'tcx>, infer_suggestable: bool) -> bool

Whether this makes sense to suggest in a diagnostic. Read more
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fn make_suggestable( self, tcx: TyCtxt<'tcx>, infer_suggestable: bool ) -> Option<T>

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impl<T> MaybeResult<T> for T

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type Error = !

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fn from(_: Result<T, <T as MaybeResult<T>>::Error>) -> T

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fn to_result(self) -> Result<T, <T as MaybeResult<T>>::Error>

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impl<T> ToOwned for Twhere T: Clone,

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type Owned = T

The resulting type after obtaining ownership.
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fn to_owned(&self) -> T

Creates owned data from borrowed data, usually by cloning. Read more
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fn clone_into(&self, target: &mut T)

Uses borrowed data to replace owned data, usually by cloning. Read more
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impl<'tcx, T> ToPredicate<'tcx, T> for T

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fn to_predicate(self, _tcx: TyCtxt<'tcx>) -> T

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impl<T, U> TryFrom<U> for Twhere U: Into<T>,

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type Error = Infallible

The type returned in the event of a conversion error.
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fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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impl<T, U> TryInto<U> for Twhere U: TryFrom<T>,

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type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.
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impl<'tcx, T> TypeVisitableExt<'tcx> for Twhere T: TypeVisitable<TyCtxt<'tcx>>,

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

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fn has_projections(&self) -> bool

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fn has_inherent_projections(&self) -> bool

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fn has_opaque_types(&self) -> bool

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fn has_generators(&self) -> bool

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fn references_error(&self) -> bool

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

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fn has_non_region_param(&self) -> bool

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fn has_infer_regions(&self) -> bool

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fn has_infer_types(&self) -> bool

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fn has_non_region_infer(&self) -> bool

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fn has_infer(&self) -> bool

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fn has_placeholders(&self) -> bool

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fn has_non_region_placeholders(&self) -> bool

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fn has_param(&self) -> bool

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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.
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fn has_erased_regions(&self) -> bool

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fn has_erasable_regions(&self) -> bool

True if there are any un-erased free regions.
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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.
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fn has_late_bound_regions(&self) -> bool

True if there are any late-bound regions
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fn has_non_region_late_bound(&self) -> bool

True if there are any late-bound non-region variables
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fn has_late_bound_vars(&self) -> bool

True if there are any late-bound variables
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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.
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impl<Tcx, T> Value<Tcx> for Twhere Tcx: DepContext,

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default fn from_cycle_error( tcx: Tcx, cycle: &[QueryInfo], _guar: ErrorGuaranteed ) -> T

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