Struct rustc_middle::ty::visit::HasEscapingVarsVisitor
source · struct HasEscapingVarsVisitor {
outer_index: DebruijnIndex,
}
Expand description
An “escaping var” is a bound var whose binder is not part of t
. A bound var can be a
bound region or a bound type.
So, for example, consider a type like the following, which has two binders:
for<’a> fn(x: for<’b> fn(&’a isize, &’b isize)) ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ outer scope ^~~~~~~~~~~~~~~~~~~~~~~~~~~~ inner scope
This type has bound regions ('a
, 'b
), but it does not have escaping regions, because the
binders of both 'a
and 'b
are part of the type itself. However, if we consider the inner
fn type, that type has an escaping region: 'a
.
Note that what I’m calling an “escaping var” is often just called a “free var”. However, we already use the term “free var”. It refers to the regions or types that we use to represent bound regions or type params on a fn definition while we are type checking its body.
To clarify, conceptually there is no particular difference between an “escaping” var and a “free” var. However, there is a big difference in practice. Basically, when “entering” a binding level, one is generally required to do some sort of processing to a bound var, such as replacing it with a fresh/placeholder var, or making an entry in the environment to represent the scope to which it is attached, etc. An escaping var represents a bound var for which this processing has not yet been done.
Fields§
§outer_index: DebruijnIndex
Anything bound by outer_index
or “above” is escaping.
Trait Implementations§
source§impl<'tcx> TypeVisitor<'tcx> for HasEscapingVarsVisitor
impl<'tcx> TypeVisitor<'tcx> for HasEscapingVarsVisitor
type BreakTy = FoundEscapingVars
fn visit_binder<T: TypeVisitable<'tcx>>(
&mut self,
t: &Binder<'tcx, T>
) -> ControlFlow<Self::BreakTy>
fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy>
fn visit_region(&mut self, r: Region<'tcx>) -> ControlFlow<Self::BreakTy>
fn visit_const(&mut self, ct: Const<'tcx>) -> ControlFlow<Self::BreakTy>
fn visit_predicate(
&mut self,
predicate: Predicate<'tcx>
) -> ControlFlow<Self::BreakTy>
Auto Trait Implementations§
impl RefUnwindSafe for HasEscapingVarsVisitor
impl Send for HasEscapingVarsVisitor
impl Sync for HasEscapingVarsVisitor
impl Unpin for HasEscapingVarsVisitor
impl UnwindSafe for HasEscapingVarsVisitor
Blanket Implementations§
source§impl<T, R> InternIteratorElement<T, R> for T
impl<T, R> InternIteratorElement<T, R> for T
type Output = R
fn intern_with<I, F>(iter: I, f: F) -> <T as InternIteratorElement<T, R>>::Outputwhere
I: Iterator<Item = T>,
F: FnOnce(&[T]) -> R,
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> Value<Tcx> for Twhere
Tcx: DepContext,
impl<Tcx, T> Value<Tcx> for Twhere
Tcx: DepContext,
default fn from_cycle_error(tcx: Tcx, _: &[QueryInfo]) -> 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: 4 bytes