Scope in rustc_hir_analysis::collect::resolve_bound_vars - Rust
Description: API documentation for the Rust `Scope` enum in crate `rustc_hir_analysis`.

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## Scope

# Enum Scope

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    enum Scope<'a, 'tcx> {
        Binder {
            bound_vars: FxIndexMap<LocalDefId, ResolvedArg>,
            scope_type: BinderScopeType,
            hir_id: HirId,
            s: &'a Scope<'a, 'tcx>,
            where_bound_origin: Option<PredicateOrigin>,
        },
        Body {
            id: BodyId,
            s: &'a Scope<'a, 'tcx>,
        },
        ObjectLifetimeDefault {
            lifetime: Option<ResolvedArg>,
            s: &'a Scope<'a, 'tcx>,
        },
        Supertrait {
            bound_vars: Vec<BoundVariableKind<'tcx>>,
            s: &'a Scope<'a, 'tcx>,
        },
        TraitRefBoundary {
            s: &'a Scope<'a, 'tcx>,
        },
        Opaque {
            def_id: LocalDefId,
            captures: &'a RefCell<FxIndexMap<ResolvedArg, LocalDefId>>,
            s: &'a Scope<'a, 'tcx>,
        },
        LateBoundary {
            s: &'a Scope<'a, 'tcx>,
            what: &'static str,
            deny_late_regions: bool,
        },
        Root {
            opt_parent_item: Option<LocalDefId>,
        },
    }

## Variants§

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### Binder

Declares lifetimes, and each can be early-bound or late-bound. The `DebruijnIndex` of late-bound lifetimes starts at `1` and it should be shifted by the number of `Binder`s in between the declaration `Binder` and the location it’s referenced from.

#### Fields

§`bound_vars: FxIndexMap<LocalDefId, ResolvedArg>`

We use an IndexMap here because we want these lifetimes in order for diagnostics.

§`scope_type: BinderScopeType`
§`hir_id: HirId`

The late bound vars for a given item are stored by `HirId` to be queried later. However, if we enter an elision scope, we have to later append the elided bound vars to the list and need to know what to append to.

§`s: &'a Scope<'a, 'tcx>`
§`where_bound_origin: Option<PredicateOrigin>`

If this binder comes from a where clause, specify how it was created. This is used to diagnose inaccessible lifetimes in APIT:

ⓘ

    fn foo(x: impl for<'a> Trait<'a, Assoc = impl Copy + 'a>) {}

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### Body

Lifetimes introduced by a fn are scoped to the call-site for that fn, if this is a fn body, otherwise the original definitions are used. Unspecified lifetimes are inferred, unless an elision scope is nested, e.g., `(&T, fn(&T) -> &T);` becomes `(&'_ T, for<'a> fn(&'a T) -> &'a T)`.

#### Fields

§`id: BodyId`
§`s: &'a Scope<'a, 'tcx>`
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### ObjectLifetimeDefault

Use a specific lifetime (if `Some`) or leave it unset (to be inferred in a function body or potentially error outside one), for the default choice of lifetime in a trait object type.

#### Fields

§`lifetime: Option<ResolvedArg>`
§`s: &'a Scope<'a, 'tcx>`
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### Supertrait

When we have nested trait refs, we concatenate late bound vars for inner trait refs from outer ones. But we also need to include any HRTB lifetimes encountered when identifying the trait that an associated type is declared on.

#### Fields

§`bound_vars: Vec<BoundVariableKind<'tcx>>`
§`s: &'a Scope<'a, 'tcx>`
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### TraitRefBoundary

#### Fields

§`s: &'a Scope<'a, 'tcx>`
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### Opaque

Remap lifetimes that appear in opaque types to fresh lifetime parameters. Given: `fn foo<'a>() -> impl MyTrait<'a> { ... }`

HIR tells us that `'a` refer to the lifetime bound on `foo`. However, typeck and borrowck for opaques work based on using a new generic type. `type MyAnonTy<'b> = impl MyTrait<'b>;`

This scope collects the mapping `'a -> 'b`.

#### Fields

§`def_id: LocalDefId`

The opaque type we are traversing.

§`captures: &'a RefCell<FxIndexMap<ResolvedArg, LocalDefId>>`

Mapping from each captured lifetime `'a` to the duplicate generic parameter `'b`.

§`s: &'a Scope<'a, 'tcx>`
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### LateBoundary

Disallows capturing late-bound vars from parent scopes.

This is necessary for something like `for<T> [(); { /* references T */ }]:`, since we don’t do something more correct like replacing any captured late-bound vars with early-bound params in the const’s own generics.

#### Fields

§`s: &'a Scope<'a, 'tcx>`
§`what: &'static str`
§`deny_late_regions: bool`
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### Root

#### Fields

§`opt_parent_item: Option<LocalDefId>`

## Implementations§

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### impl<'a, 'tcx> Scope<'a, 'tcx>

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#### fn debug_truncated(&self) -> impl Debug

## Trait Implementations§

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### impl<'a, 'tcx> Debug for Scope<'a, 'tcx>

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

Formats the value using the given formatter. Read more

## Auto Trait Implementations§

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### impl<'a, 'tcx> !DynSend for Scope<'a, 'tcx>

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### impl<'a, 'tcx> !DynSync for Scope<'a, 'tcx>

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### impl<'a, 'tcx> !RefUnwindSafe for Scope<'a, 'tcx>

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### impl<'a, 'tcx> !Send for Scope<'a, 'tcx>

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### impl<'a, 'tcx> !Sync for Scope<'a, 'tcx>

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### impl<'a, 'tcx> !UnwindSafe for Scope<'a, 'tcx>

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### impl<'a, 'tcx> Freeze for Scope<'a, 'tcx>

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### impl<'a, 'tcx> Unpin for Scope<'a, 'tcx>

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### impl<'a, 'tcx> UnsafeUnpin for Scope<'a, 'tcx>

## 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 T
where T: 'static + ?Sized,

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#### fn type_id(&self) -> TypeId

Gets the `TypeId` of `self`. Read more
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### impl<T> Borrow<T> for T
where 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 T
where 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) -> R
where 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<T> ErasedDestructor for T
where T: 'static,

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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> Instrument for T

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#### fn instrument(self, span: Span) -> Instrumented<Self>

Instruments this type with the provided `Span`, returning an `Instrumented` wrapper. Read more
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#### fn in_current_span(self) -> Instrumented<Self>

Instruments this type with the current `Span`, returning an `Instrumented` wrapper. Read more
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### impl<T, U> Into<U> for T
where 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<T> IntoEither for T

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#### fn into_either(self, into_left: bool) -> Either<Self, Self>

Converts `self` into a `Left` variant of `Either<Self, Self>` if `into_left` is `true`. Converts `self` into a `Right` variant of `Either<Self, Self>` otherwise. Read more
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#### fn into_either_with<F>(self, into_left: F) -> Either<Self, Self>
where F: FnOnce(&Self) -> bool,

Converts `self` into a `Left` variant of `Either<Self, Self>` if `into_left(&self)` returns `true`. Converts `self` into a `Right` variant of `Either<Self, Self>` otherwise. Read more
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### impl<K> IntoQueryKey<K> for K

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#### fn into_query_key(self) -> K

Argument conversion from `Self` to `K`. This should always be a very cheap conversion, e.g. `LocalDefId::to_def_id`.
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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> Pointable for T

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#### const ALIGN: usize

The alignment of pointer.
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#### type Init = T

The type for initializers.
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#### unsafe fn init(init: <T as Pointable>::Init) -> usize

Initializes a with the given initializer. Read more
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#### unsafe fn deref<'a>(ptr: usize) -> &'a T

Dereferences the given pointer. Read more
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#### unsafe fn deref_mut<'a>(ptr: usize) -> &'a mut T

Mutably dereferences the given pointer. Read more
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#### unsafe fn drop(ptr: usize)

Drops the object pointed to by the given pointer. Read more
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### impl<T> Same for T

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#### type Output = T

Should always be `Self`
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### impl<T, U> TryFrom<U> for T
where 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 T
where 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<I, T, U> Upcast<I, U> for T
where U: UpcastFrom<I, T>,

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#### fn upcast(self, interner: I) -> U

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### impl<I, T> UpcastFrom<I, T> for T

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#### fn upcast_from(from: T, _tcx: I) -> T

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### impl<V, T> VZip<V> for T
where V: MultiLane<T>,

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#### fn vzip(self) -> V

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### impl<T> WithSubscriber for T

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#### fn with_subscriber<S>(self, subscriber: S) -> WithDispatch<Self>
where S: Into<Dispatch>,

Attaches the provided `Subscriber` to this type, returning a `WithDispatch` wrapper. Read more
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#### fn with_current_subscriber(self) -> WithDispatch<Self>

Attaches the current default `Subscriber` to this type, returning a `WithDispatch` wrapper. Read more

## Layout§

Note: Most layout information is completely unstable and may even differ between compilations. The only exception is types with certain `repr(...)` attributes. Please see the Rust Reference's “Type Layout” chapter for details on type layout guarantees.

Size: 80 bytes

Size for each variant:

- `Binder`: 80 bytes
- `Body`: 24 bytes
- `ObjectLifetimeDefault`: 32 bytes
- `Supertrait`: 40 bytes
- `TraitRefBoundary`: 16 bytes
- `Opaque`: 32 bytes
- `LateBoundary`: 40 bytes
- `Root`: 12 bytes