plum

#treesitter#compiler#wasm

git clone https://git.pyrossh.dev/plum

A statically typed, imperative programming language inspired by rust, python

acc2f1f — Peter John 2026-11-01T20:55:22+05:30 
fix: exhaustiveness through union member sub-patterns
Files changed (3) hide show
  1. plum-checker/src/lib.rs +17 -3
  2. plum-checker/tests/unions_pattern_test.rs +29 -0
  3. plum-examples/match.plum +0 -3
plum-checker/src/lib.rs CHANGED
@@ -2654,10 +2654,24 @@ fn coverRows<'a>(
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  continue;
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  }
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  if c.member {
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- if !fs.iter().all(patCatchAll) {
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+ if fs.iter().all(patCatchAll) {
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+ row.extend(std::iter::repeat(&COVER_WILDCARD).take(c.fields.len()));
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+ } else {
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+ // Refutable sub-patterns: the hidden variant's one field is
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+ // the member type, matched by the user's pattern itself (a
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+ // record destructures its own fields) or, for a non-record
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+ // member, by its single sub-pattern.
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+ let is_record = c.fields.first().and_then(nominalName).is_some_and(|m| {
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+ ctx.enum_variants.get(m).is_some_and(|i| i.enum_name == m)
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+ });
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+ if is_record {
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+ row.push(r[0]);
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+ } else if fs.len() == 1 {
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+ row.push(&fs[0]);
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+ } else {
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- continue;
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+ continue;
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+ }
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  }
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- row.extend(std::iter::repeat(&COVER_WILDCARD).take(c.fields.len()));
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  } else if let ast::CasePattern::Name(_) = r[0] {
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  // Bare `Circle` against a payload variant: tag check only.
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  row.extend(std::iter::repeat(&COVER_WILDCARD).take(c.fields.len()));
plum-checker/tests/unions_pattern_test.rs CHANGED
@@ -107,3 +107,32 @@ fn primitive_member_narrows() {
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  r.unwrap();
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  assert_eq!(p.narrowings.len(), 2);
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  }
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+
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+ const NEST: &str = "\
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+ enum IntOpt = Present | Absent
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+ record Present(v: Int)
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+ enum Nested = Wrap | Empty
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+ record Wrap(v: IntOpt)
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+ record Point(x: Int, y: Int)
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+ enum Geo = Located | Nowhere
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+ record Located(p: Point)
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+ ";
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+
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+ #[test]
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+ fn refutable_member_subpatterns_exhaustive() {
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+ let (r, _) = run(&format!("{NEST}\nfun f(n: Nested) -> Int =\n match n\n Wrap(Present(v)) => v\n Wrap(Absent) => -1\n Empty => 0"));
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+ r.unwrap();
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+ let (r, _) = run(&format!("{NEST}\nfun f(g: Geo) -> Int =\n match g\n Located(Point(x, y)) => x + y\n Nowhere => 0"));
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+ r.unwrap();
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+ }
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+
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+ #[test]
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+ fn refutable_member_subpatterns_missing_case() {
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+ let (r, _) = run(&format!("{NEST}\nfun f(n: Nested) -> Int =\n match n\n Wrap(Present(v)) => v\n Empty => 0"));
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+ let e = errs(r);
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+ assert!(e.contains("non-exhaustive match") && e.contains("Absent"), "{e}");
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+ assert!(!e.contains("__"), "{e}");
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+ let (r, _) = run(&format!("{NEST}\nfun f(n: Nested) -> Int =\n match n\n Wrap(Present(v)) => v\n Wrap(Absent) => -1"));
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+ let e = errs(r);
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+ assert!(e.contains("missing Empty") && !e.contains("__"), "{e}");
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+ }
plum-examples/match.plum CHANGED
@@ -54,7 +54,6 @@ fun unwrapNested(n: Nested) -> Int =
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  match n
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  Wrap(Present(v)) => v
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  Wrap(Absent) => -1
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- Wrap(_) => -2
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  Empty => 0
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  enum Reading[T] = Sample[T] | NoSignal
@@ -72,7 +71,6 @@ fun unwrapGenericBox(b: GenericBox[Reading[Int]]) -> Int =
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  match b
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  GFull(Sample(v)) => v
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  GFull(NoSignal) => -1
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- GFull(_) => -2
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  GEmpty => 0
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  enum RecOption = RSome | RNone
@@ -156,7 +154,6 @@ enum Shape =
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  match self
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  Circle(Point(x, y)) => x + y
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  Square(Point(x, y)) => x * y
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- _ => 0
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157
 
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  record Circle(v: Point)
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  record Square(v: Point)