feat: implement an Expr trait

argus-core/src/expr/traits.rs

@@ -0,0 +1,53 @@
+use std::any::Any;
+
+use super::iter::AstIter;
+
+/// A trait representing expressions
+pub trait Expr {
+    fn args(&self) -> Vec<&dyn Expr>;
+
+    fn as_any(&self) -> &dyn Any;
+
+    fn iter(&self) -> AstIter<'_>
+    where
+        Self: Sized,
+    {
+        AstIter::new(self)
+    }
+}
+
+impl dyn Expr {
+    pub fn downcast_expr_ref<T>(&self) -> Option<&T>
+    where
+        T: Any,
+    {
+        self.as_any().downcast_ref::<T>()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::super::{arbitrary, BoolExpr, NumExpr};
+    use super::*;
+    use proptest::prelude::*;
+
+    proptest! {
+        #[test]
+        fn downcast_expr_bool(bool_expr in arbitrary::bool_expr()) {
+            let expr_ref = bool_expr.as_ref() as &dyn Expr;
+
+            let downcast_ref = expr_ref.downcast_expr_ref::<BoolExpr>().unwrap();
+            assert_eq!(downcast_ref, bool_expr.as_ref());
+        }
+    }
+
+    proptest! {
+        #[test]
+        fn downcast_expr_num(num_expr in arbitrary::num_expr()) {
+            let expr_ref = num_expr.as_ref() as &dyn Expr;
+
+            let downcast_ref = expr_ref.downcast_expr_ref::<NumExpr>().unwrap();
+            assert_eq!(downcast_ref, num_expr.as_ref());
+        }
+    }
+}