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correct list pattern match checking to add extra anythings for patterns with rest

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Brendan Hansknecht 2023-11-20 14:35:59 -08:00
parent ee10af2c68
commit 37a8bbd87c
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1 changed files with 28 additions and 6 deletions
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34
crates/compiler/exhaustive/src/lib.rs
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@ -389,7 +389,6 @@ pub fn is_useful(mut old_matrix: PatternMatrix, mut vector: Row) -> bool {
vector.extend(args);
} else {
// TODO turn this into an iteration over the outer loop rather than bouncing
vector.extend(args);
for list_ctor in spec_list_ctors {
let mut old_matrix = old_matrix.clone();
let mut spec_matrix = Vec::with_capacity(old_matrix.len());
@ -400,7 +399,31 @@ pub fn is_useful(mut old_matrix: PatternMatrix, mut vector: Row) -> bool {
&mut spec_matrix,
);
if is_useful(spec_matrix, vector.clone()) {
// Add Anythings for the missing elements.
let full_args = if let ListArity::Slice(before, _) = arity {
if arity.min_len() < list_ctor.min_len() {
let (before, after) = args.split_at(before);
let num_extra_wildcards =
list_ctor.min_len() - arity.min_len();
let extra_wildcards =
std::iter::repeat(&Anything).take(num_extra_wildcards);
before
.iter()
.chain(extra_wildcards)
.chain(after)
.cloned()
.collect()
} else {
args.clone()
}
} else {
args.clone()
};
let mut nested_vector = vector.clone();
nested_vector.extend(full_args);
if is_useful(spec_matrix, nested_vector) {
return true;
}
}
@ -527,9 +550,8 @@ fn specialize_row_by_list(spec_arity: ListArity, mut row: Row) -> Option<Row> {
debug_assert!(spec_arity.min_len() > this_arity.min_len());
match this_arity {
ListArity::Exact(_) => internal_error!("exact-sized lists cannot cover lists of other minimum length"),
ListArity::Slice(before, after) => {
let before = &args[..before];
let after = &args[this_arity.min_len() - after..];
ListArity::Slice(before, _) => {
let (before, after) = args.split_at(before);
let num_extra_wildcards = spec_arity.min_len() - this_arity.min_len();
let extra_wildcards = std::iter::repeat(&Anything).take(num_extra_wildcards);
@ -847,7 +869,7 @@ fn build_list_ctors_covering_patterns(
}
(max_prefix_len, max_suffix_len)
};
let l = inf_cover_prefix + inf_cover_suffix;
let l = inf_cover_prefix + inf_cover_suffix + 1;
let exact_size_lists = (min_len..l) // exclusive
.map(ListArity::Exact);