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ConstantValue is the only other ctor allowed when subtracting from slice ctors

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This commit is contained in:
Nadrieril 2019-11-17 19:24:48 +00:00
parent bd0e3ccd0b
commit 7f5e0441e2
1 changed files with 39 additions and 33 deletions

72
src/librustc_mir/hair/pattern/_match.rs

@ -742,44 +742,50 @@ impl<'tcx> Constructor<'tcx> {
Single | Variant(_) | ConstantValue(..) | FloatRange(..) => {
if other_ctors.iter().any(|c| c == self) { vec![] } else { vec![self.clone()] }
}
&Slice(slice) => match slice.value_kind() {
FixedLen(self_len) => {
let overlaps = |c: &Constructor<'_>| match *c {
Slice(other_slice) => other_slice.value_kind().covers_length(self_len),
_ => false,
};
if other_ctors.iter().any(overlaps) { vec![] } else { vec![Slice(slice)] }
}
VarLen(..) => {
let mut remaining_slices = vec![slice.value_kind()];
&Slice(slice) => {
let mut other_slices = other_ctors
.iter()
.filter_map(|c: &Constructor<'_>| match c {
Slice(slice) => Some(*slice),
// FIXME(#65413): We ignore `ConstantValue`s here.
ConstantValue(..) => None,
_ => bug!("bad slice pattern constructor {:?}", c),
})
.map(Slice::value_kind);
// For each used slice, subtract from the current set of slices.
for other_ctor in other_ctors {
let other_slice = match other_ctor {
Slice(slice) => slice.value_kind(),
// FIXME(#65413): If `other_ctor` is not a slice, we assume it doesn't
// cover any value here.
_ => continue,
};
remaining_slices = remaining_slices
.into_iter()
.flat_map(|remaining_slice| remaining_slice.subtract(other_slice))
.collect();
// If the constructors that have been considered so far already cover
// the entire range of `self`, no need to look at more constructors.
if remaining_slices.is_empty() {
break;
match slice.value_kind() {
FixedLen(self_len) => {
if other_slices.any(|other_slice| other_slice.covers_length(self_len)) {
vec![]
} else {
vec![Slice(slice)]
}
}
kind @ VarLen(..) => {
let mut remaining_slices = vec![kind];
remaining_slices
.into_iter()
.map(|kind| Slice { array_len: slice.array_len, kind })
.map(Slice)
.collect()
// For each used slice, subtract from the current set of slices.
for other_slice in other_slices {
remaining_slices = remaining_slices
.into_iter()
.flat_map(|remaining_slice| remaining_slice.subtract(other_slice))
.collect();
// If the constructors that have been considered so far already cover
// the entire range of `self`, no need to look at more constructors.
if remaining_slices.is_empty() {
break;
}
}
remaining_slices
.into_iter()
.map(|kind| Slice { array_len: slice.array_len, kind })
.map(Slice)
.collect()
}
}
},
}
IntRange(self_range) => {
let mut remaining_ranges = vec![self_range.clone()];
for other_ctor in other_ctors {