Assert against empty conjunctions and disjunctions

src/ast.rs

@@ -491,6 +491,8 @@ impl Formula
 {
 	pub fn and(arguments: Formulas) -> Self
 	{
+		assert!(!arguments.is_empty());
+
 		Self::And(arguments)
 	}
 
@@ -566,6 +568,8 @@ impl Formula
 
 	pub fn or(arguments: Formulas) -> Self
 	{
+		assert!(!arguments.is_empty());
+
 		Self::Or(arguments)
 	}