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Rewrite add_type_requirement to use Entry and check for empty sets.

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Richard Newman 2018-01-29 14:24:17 -08:00
parent c46a13f9e1
commit 13dd67f15a
1 changed files with 31 additions and 13 deletions
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44
query-algebrizer/src/clauses/mod.rs
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@ -557,21 +557,39 @@ impl ConjoiningClauses {
/// the type requirements in place prior to calling `add_type_requirement`.
///
/// If the intersection will leave the variable so that it cannot be any
/// type, we'll call mark_known_empty.
/// type, we'll call `mark_known_empty`.
pub fn add_type_requirement(&mut self, var: Variable, types: ValueTypeSet) {
let existing = self.required_types.get(&var).cloned().unwrap_or(ValueTypeSet::any());
// We have an existing requirement. The new requirement will be
// the intersection, but we'll mark_known_empty if that's empty.
let intersection = types.intersection(&existing);
if intersection.is_empty() {
self.mark_known_empty(EmptyBecause::TypeMismatch {
var: var.clone(),
existing: existing,
desired: types,
});
if types.is_empty() {
// This shouldn't happen, but if it does…
self.mark_known_empty(EmptyBecause::NoValidTypes(var));
return;
}
self.required_types.insert(var, intersection);
// Optimize for the empty case.
let empty_because = match self.required_types.entry(var.clone()) {
Entry::Vacant(entry) => {
entry.insert(types);
return;
},
Entry::Occupied(mut entry) => {
// We have an existing requirement. The new requirement will be
// the intersection, but we'll `mark_known_empty` if that's empty.
let existing = *entry.get();
let intersection = types.intersection(&existing);
entry.insert(intersection);
if !intersection.is_empty() {
return;
}
EmptyBecause::TypeMismatch {
var: var,
existing: existing,
desired: types,
}
},
};
self.mark_known_empty(empty_because);
}
/// Like `constrain_var_to_type` but in reverse: this expands the set of types