enum Scope<'a> {
Binder {
lifetimes: FxIndexMap<LocalDefId, Region>,
scope_type: BinderScopeType,
hir_id: HirId,
s: &'a Scope<'a>,
where_bound_origin: Option<PredicateOrigin>,
},
Body {
id: BodyId,
s: &'a Scope<'a>,
},
Elision {
s: &'a Scope<'a>,
},
ObjectLifetimeDefault {
lifetime: Option<Region>,
s: &'a Scope<'a>,
},
Supertrait {
lifetimes: Vec<BoundVariableKind>,
s: &'a Scope<'a>,
},
TraitRefBoundary {
s: &'a Scope<'a>,
},
Root,
}
Variants
Binder
Fields
lifetimes: FxIndexMap<LocalDefId, Region>
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>) {}
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.
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)
.
Elision
Fields
s: &'a Scope<'a>
A scope which either determines unspecified lifetimes or errors on them (e.g., due to ambiguity).
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.
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.
TraitRefBoundary
Fields
s: &'a Scope<'a>
Root
Trait Implementations
Auto Trait Implementations
impl<'a> RefUnwindSafe for Scope<'a>
impl<'a> Send for Scope<'a>
impl<'a> Sync for Scope<'a>
impl<'a> Unpin for Scope<'a>
impl<'a> UnwindSafe for Scope<'a>
Blanket Implementations
sourceimpl<T> BorrowMut<T> for Twhere
T: ?Sized,
impl<T> BorrowMut<T> for Twhere
T: ?Sized,
const: unstable · sourcefn borrow_mut(&mut self) -> &mut T
fn borrow_mut(&mut self) -> &mut T
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
: 79 bytesBody
: 23 bytesElision
: 15 bytesObjectLifetimeDefault
: 31 bytesSupertrait
: 39 bytesTraitRefBoundary
: 15 bytesRoot
: 0 bytes