Check that predicate expression isn't Nothing

1 files changed, 1 insertions, 0 deletions

diff --git a/src/c.bqn b/src/c.bqn
index f94e87e6..c4889f7a 100644
--- a/src/c.bqn
+++ b/src/c.bqn
@@ -233,6 +233,7 @@ Parse ← {r‿vn‿i‿e‿def←𝕨⋄nv←≠vn
   tr←1≤er←ir⊏˜IT»ps                         # er: expression role; tr: train or modifier expression
   no←0⌈-ir⋄ne←0⌈-er⋄nei↩g⋄nx⊏˜↩gr           # Nothing value; expression
   "Nothing (·) cannot be assigned"_nerr ne×a
+  "Can't use Nothing (·) as predicate"_nerr ne×𝕩=2+⊑bH
   oa←⌽/hg<op←(er<2)∧r≥2⋄ro←op∨«op∧m2←r=3    # op: active modifiers; ro: mod or right operand
   "Missing operand"_nerr op×2(«⌈m2×»)no⌈2×m2≥ro∨r∊↕2
   s←𝕩=sep⋄fo←𝕩∊⟨2+⊑bB,1+⊑bH⟩                # Separators, function open { or ;