Simplify tuple flattening and destructuring

The `flatten_tuple` function was unnecessarily recursive. It can now
simply return the elements of the tuple directly. The VM's destructuring
logic has been updated to handle nested destructuring more efficiently.
A new integration test case for multi-level destructuring has been
added.

examples/tuple-struct.myc

@@ -0,0 +1,12 @@
+(do
+     (def pipe (fn [conf]
+       (do
+          (def [str s] conf)
+          (def [f ss] s)
+          ["Symbol:" str "field:" f "id:" ss]
+       )
+      )
+     )
+
+     (pipe ["btc" [:close "cls"]])
+   )

src/ast/compiler/specializer.rs

@@ -308,13 +308,7 @@ impl Specializer {
 
     fn flatten_tuple(&self, node: AnalyzedNode) -> Vec<AnalyzedNode> {
         match node.kind {
-            BoundKind::Tuple { elements } => {
+            BoundKind::Tuple { elements } => elements,
-                let mut flat = Vec::new();
-                for el in elements {
-                    flat.extend(self.flatten_tuple(el));
-                }
-                flat
-            }
             _ => vec![node],
         }
     }

src/ast/vm.rs

@@ -416,7 +416,15 @@ impl VM {
                                 {
                                     self.stack.extend(arg_vals);
                                 } else {
-                                    self.unpack(&closure.parameter_node, &arg_vals, &mut 0)?;
+                                    // Map each parameter pattern to the provided arguments
+                                    if let BoundKind::Tuple { elements } = &closure.parameter_node.kind {
+                                        let mut offset = 0;
+                                        for el in elements {
+                                            self.unpack(el, &arg_vals, &mut offset)?;
+                                        }
+                                    } else {
+                                        self.unpack(&closure.parameter_node, &arg_vals, &mut 0)?;
+                                    }
                                 }
                                 let result = self.eval_internal(obs, &closure.exec_node);
                                 self.frames.pop();

src/integration_test.rs

@@ -369,4 +369,25 @@ mod tests {
             }
         }
     }
+
+    #[test]
+    fn test_multi_level_destructuring() {
+        let env = Environment::new();
+        let source = "(do
+          (def pipe (fn [conf]
+            (do
+               (def [str s] conf)
+               (def [f ss] s)
+               [\"Symbol:\" str \"field:\" f \"id:\" ss]
+            )
+           )
+          )
+          (pipe [\"btc\" [:close \"cls\"]]))";
+
+        let res = env.run_script(source).unwrap();
+        assert_eq!(
+            format!("{}", res),
+            "[\"Symbol:\" \"btc\" \"field:\" :close \"id:\" \"cls\"]"
+        );
+    }
 }