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Special-case subtracting from a range if that range is not an IntRange

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Nadrieril 2019-11-09 09:43:15 +00:00
parent 6de7afdf95
commit c6c862574d
1 changed files with 36 additions and 21 deletions
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57
src/librustc_mir/hair/pattern/_match.rs
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@ -763,31 +763,46 @@ impl<'tcx> Constructor<'tcx> {
remaining_ctors
}
ConstantRange(..) | ConstantValue(..) => {
let mut remaining_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.
remaining_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.
remaining_ctors = interval.subtract_from(tcx, param_env, remaining_ctors);
if let Some(_self_range) = IntRange::from_ctor(tcx, param_env, self) {
let mut remaining_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.
remaining_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.
remaining_ctors =
interval.subtract_from(tcx, param_env, remaining_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 remaining_ctors.is_empty() {
break;
}
}
// 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 remaining_ctors.is_empty() {
break;
// If a constructor has not been matched, then it is missing.
// We add `remaining_ctors` instead of `self`, because then we can
// provide more detailed error information about precisely which
// ranges have been omitted.
remaining_ctors
} else {
if other_ctors.iter().any(|c| {
c == self
// FIXME(Nadrieril): This condition looks fishy
|| IntRange::from_ctor(tcx, param_env, c).is_some()
}) {
vec![]
} else {
vec![self.clone()]
}
}
// If a constructor has not been matched, then it is missing.
// We add `remaining_ctors` instead of `self`, because then we can
// provide more detailed error information about precisely which
// ranges have been omitted.
remaining_ctors
}
// This constructor is never covered by anything else
NonExhaustive => vec![NonExhaustive],