Fix function shadowing by reversing scope traversal

Author: Rafael-Sapienza

src/environment/environment.rs

@@ -200,7 +200,10 @@ impl<A: Clone + Debug> Environment<A> {
         for (func_signature, func) in &self.globals.functions {
             all_functions.insert(func_signature.clone(), func.clone());
         }
-        for scope in self.stack.iter() {
+        // It is necessary to traverse the scope stack from bottom to top
+        // so that functions defined in inner scopes can shadow those
+        // defined in outer scopes.
+        for scope in self.stack.iter().rev() {
             for (func_signature, func) in &scope.functions {
                 all_functions.insert(func_signature.clone(), func.clone());
             }