wip addin syntax parser

src/middleend/visit_ast.rs

@@ -136,6 +136,8 @@ pub fn walk_expr<V: Visitor>(visitor: &mut V, expr: &AstNode) -> LoxResult<()> {
             visitor.visit_expr(increment)?;
             visitor.visit_expr(body)
         }
+        // Struct declarations carry only type information, no child expressions.
+        Expr::Struct { .. } => Ok(()),
     }
 }