Enum rustc_mir_build::thir::pattern::usefulness::Usefulness
source · enum Usefulness<'p, 'tcx> {
NoWitnesses {
useful: bool,
},
WithWitnesses(Vec<Witness<'p, 'tcx>>),
}
Expand description
This carries the results of computing usefulness, as described at the top of the file. When
checking usefulness of a match branch, we use the NoWitnesses
variant, which also keeps track
of potential unreachable sub-patterns (in the presence of or-patterns). When checking
exhaustiveness of a whole match, we use the WithWitnesses
variant, which carries a list of
witnesses of non-exhaustiveness when there are any.
Which variant to use is dictated by ArmType
.
Variants§
NoWitnesses
If we don’t care about witnesses, simply remember if the pattern was useful.
WithWitnesses(Vec<Witness<'p, 'tcx>>)
Carries a list of witnesses of non-exhaustiveness. If empty, indicates that the whole pattern is unreachable.
Implementations§
source§impl<'p, 'tcx> Usefulness<'p, 'tcx>
impl<'p, 'tcx> Usefulness<'p, 'tcx>
fn new_useful(preference: ArmType) -> Self
fn new_not_useful(preference: ArmType) -> Self
fn is_useful(&self) -> bool
sourcefn extend(&mut self, other: Self)
fn extend(&mut self, other: Self)
Combine usefulnesses from two branches. This is an associative operation.
sourcefn apply_constructor(
self,
pcx: &PatCtxt<'_, 'p, 'tcx>,
matrix: &Matrix<'p, 'tcx>,
ctor: &Constructor<'tcx>
) -> Self
fn apply_constructor( self, pcx: &PatCtxt<'_, 'p, 'tcx>, matrix: &Matrix<'p, 'tcx>, ctor: &Constructor<'tcx> ) -> Self
After calculating usefulness after a specialization, call this to reconstruct a usefulness that makes sense for the matrix pre-specialization. This new usefulness can then be merged with the results of specializing with the other constructors.
Trait Implementations§
Auto Trait Implementations§
impl<'p, 'tcx> !RefUnwindSafe for Usefulness<'p, 'tcx>
impl<'p, 'tcx> !Send for Usefulness<'p, 'tcx>
impl<'p, 'tcx> !Sync for Usefulness<'p, 'tcx>
impl<'p, 'tcx> Unpin for Usefulness<'p, 'tcx>
impl<'p, 'tcx> !UnwindSafe for Usefulness<'p, 'tcx>
Blanket Implementations§
source§impl<T> BorrowMut<T> for Twhere
T: ?Sized,
impl<T> BorrowMut<T> for Twhere T: ?Sized,
source§fn 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: 24 bytes
Size for each variant:
NoWitnesses
: 9 bytesWithWitnesses
: 24 bytes