[checker][pattern-matching] Add nothing as a convenience factory fu…

…nction
SamChou19815 · Oct 28, 2023 · d7109fe · d7109fe
1 parent 0bc5244
commit d7109fe
Showing 1 changed file with 8 additions and 0 deletions.
diff --git a/crates/samlang-core/src/checker/pattern_matching.rs b/crates/samlang-core/src/checker/pattern_matching.rs
@@ -50,6 +50,10 @@ impl AbstractPatternNode {
     }))
   }
 
+  pub(super) fn nothing() -> Self {
+    Self(Rc::new(AbstractPatternNodeInner::Or(Vec::with_capacity(0))))
+  }
+
   pub(super) fn or(possibilities: Vec<AbstractPatternNode>) -> Self {
     Self(Rc::new(AbstractPatternNodeInner::Or(possibilities)))
   }
@@ -405,6 +409,10 @@ mod tests {
       &[&[P::enum_(OPTION_NONE), P::wildcard()], &[P::wildcard(), P::enum_(OPTION_NONE)],],
       &[P::variant(OPTION_SOME, vec![P::wildcard()]), P::variant(OPTION_SOME, vec![P::wildcard()])]
     ));
+    assert!(!useful(
+      &[&[P::enum_(OPTION_NONE), P::wildcard()], &[P::wildcard(), P::enum_(OPTION_NONE)],],
+      &[P::nothing()]
+    ));
     assert!(!useful(
       &[
         &[P::enum_(OPTION_NONE), P::wildcard()],