pub struct RegionConstraintData<'tcx> {
pub constraints: BTreeMap<Constraint<'tcx>, SubregionOrigin<'tcx>, Global>,
pub member_constraints: Vec<MemberConstraint<'tcx>, Global>,
pub verifys: Vec<Verify<'tcx>, Global>,
pub givens: HashSet<(Region<'tcx>, RegionVid), BuildHasherDefault<FxHasher>>,
}
Expand description
The full set of region constraints gathered up by the collector. Describes constraints between the region variables and other regions, as well as other conditions that must be verified, or assumptions that can be made.
Fields
constraints: BTreeMap<Constraint<'tcx>, SubregionOrigin<'tcx>, Global>
Constraints of the form A <= B
, where either A
or B
can
be a region variable (or neither, as it happens).
member_constraints: Vec<MemberConstraint<'tcx>, Global>
Constraints of the form R0 member of [R1, ..., Rn]
, meaning that
R0
must be equal to one of the regions R1..Rn
. These occur
with impl Trait
quite frequently.
verifys: Vec<Verify<'tcx>, Global>
A “verify” is something that we need to verify after inference is done, but which does not directly affect inference in any way.
An example is a A <= B
where neither A
nor B
are
inference variables.
givens: HashSet<(Region<'tcx>, RegionVid), BuildHasherDefault<FxHasher>>
A “given” is a relationship that is known to hold. In particular, we often know from closure fn signatures that a particular free region must be a subregion of a region variable:
foo.iter().filter(<’a> |x: &’a &’b T| …)
In situations like this, 'b
is in fact a region variable
introduced by the call to iter()
, and 'a
is a bound region
on the closure (as indicated by the <'a>
prefix). If we are
naive, we wind up inferring that 'b
must be 'static
,
because we require that it be greater than 'a
and we do not
know what 'a
is precisely.
This hashmap is used to avoid that naive scenario. Basically
we record the fact that 'a <= 'b
is implied by the fn
signature, and then ignore the constraint when solving
equations. This is a bit of a hack but seems to work.
Auto Trait Implementations
impl<'tcx> !RefUnwindSafe for RegionConstraintData<'tcx>
impl<'tcx> !Send for RegionConstraintData<'tcx>
impl<'tcx> !Sync for RegionConstraintData<'tcx>
impl<'tcx> Unpin for RegionConstraintData<'tcx>
impl<'tcx> !UnwindSafe for RegionConstraintData<'tcx>
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: 104 bytes