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Simplify arity and branching calculation

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Ayaz Hafiz 2022-11-01 15:33:23 -05:00
parent 0706615d29
commit 27b9dd8253
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3 changed files with 46 additions and 81 deletions
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27
crates/compiler/exhaustive/src/lib.rs
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@ -102,22 +102,19 @@ impl ListArity {
/// Could this list pattern include list pattern arity `other`?
fn covers_arities_of(&self, other: &Self) -> bool {
match (self, other) {
(ListArity::Exact(l), ListArity::Exact(r)) => l == r,
(ListArity::Exact(this_exact), ListArity::Slice(other_left, other_right)) => {
// [_, _, _] can only cover [_, _, .., _]
*this_exact == (other_left + other_right)
self.covers_length(other.min_len())
}
pub fn covers_length(&self, length: usize) -> bool {
match self {
ListArity::Exact(l) => {
// [_, _, _] can only cover [_, _, _]
*l == length
}
(ListArity::Slice(this_left, this_right), ListArity::Exact(other_exact)) => {
// [_, _, .., _] can cover [_, _, _], [_, _, _, _], [_, _, _, _, _], and so on
(this_left + this_right) <= *other_exact
}
(
ListArity::Slice(this_left, this_right),
ListArity::Slice(other_left, other_right),
) => {
// [_, _, .., _] can cover [_, _, .., _], [_, .., _, _], [_, _, .., _, _], [_, _, _, .., _, _], and so on
(this_left + this_right) <= (other_left + other_right)
ListArity::Slice(head, tail) => {
// [_, _, .., _] can cover infinite arities >=3 , including
// [_, _, .., _], [_, .., _, _], [_, _, .., _, _], [_, _, _, .., _, _], and so on
head + tail <= length
}
}
}