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Factor out constructor subtraction

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Nadrieril 2019-10-27 16:58:04 +00:00 committed by Nadrieril
parent 92101b7655
commit b7fa9f12ca
1 changed files with 36 additions and 27 deletions
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63
src/librustc_mir/hair/pattern/_match.rs
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@ -646,6 +646,41 @@ impl<'tcx> Constructor<'tcx> {
}
}
// Returns the set of constructors covered by `self` but not by
// anything in `other_ctors`.
fn subtract_ctors(
&self,
tcx: TyCtxt<'tcx>,
param_env: ty::ParamEnv<'tcx>,
other_ctors: &Vec<Constructor<'tcx>>,
) -> Vec<Constructor<'tcx>> {
let mut refined_ctors = vec![self.clone()];
for other_ctor in other_ctors {
if other_ctor == self {
// If a constructor appears in a `match` arm, we can
// eliminate it straight away.
refined_ctors = vec![]
} else if let Some(interval) = IntRange::from_ctor(tcx, param_env, other_ctor) {
// Refine the required constructors for the type by subtracting
// the range defined by the current constructor pattern.
refined_ctors = interval.subtract_from(tcx, param_env, refined_ctors);
}
// If the constructor patterns that have been considered so far
// already cover the entire range of values, then we know the
// constructor is not missing, and we can move on to the next one.
if refined_ctors.is_empty() {
break;
}
}
// If a constructor has not been matched, then it is missing.
// We add `refined_ctors` instead of `self`, because then we can
// provide more detailed error information about precisely which
// ranges have been omitted.
refined_ctors
}
/// This returns one wildcard pattern for each argument to this constructor.
fn wildcard_subpatterns<'a>(
&self,
@ -1313,33 +1348,7 @@ impl<'tcx> MissingConstructors<'tcx> {
/// Iterate over all_ctors \ used_ctors
fn iter<'a>(&'a self) -> impl Iterator<Item = Constructor<'tcx>> + Captures<'a> {
self.all_ctors.iter().flat_map(move |req_ctor| {
let mut refined_ctors = vec![req_ctor.clone()];
for used_ctor in &self.used_ctors {
if used_ctor == req_ctor {
// If a constructor appears in a `match` arm, we can
// eliminate it straight away.
refined_ctors = vec![]
} else if let Some(interval) =
IntRange::from_ctor(self.tcx, self.param_env, used_ctor)
{
// Refine the required constructors for the type by subtracting
// the range defined by the current constructor pattern.
refined_ctors = interval.subtract_from(self.tcx, self.param_env, refined_ctors);
}
// If the constructor patterns that have been considered so far
// already cover the entire range of values, then we know the
// constructor is not missing, and we can move on to the next one.
if refined_ctors.is_empty() {
break;
}
}
// If a constructor has not been matched, then it is missing.
// We add `refined_ctors` instead of `req_ctor`, because then we can
// provide more detailed error information about precisely which
// ranges have been omitted.
refined_ctors
req_ctor.subtract_ctors(self.tcx, self.param_env, &self.used_ctors)
})
}
}