Enum Scope

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

Variants

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 Binders 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>

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>) {}

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>

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>

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>

s: &'a Scope<'a>

TraitRefBoundary

Fields

s: &'a Scope<'a>

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>

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>

what: &'static str

deny_late_regions: bool

Root

Fields

opt_parent_item: Option<LocalDefId>

Trait Implementations

impl<'a> Debug for Scope<'a>

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

Formats the value using the given formatter.

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