Refactor Destructure to handle assignments

Renames `DefDestructure` to `Destructure` to better reflect its use in
both definitions and assignments.
Introduces `bind_assign_pattern` to handle assignment destructuring in
the binder.
Adds `test_assign_destructuring` to verify assignment destructuring
functionality.

src/ast/vm.rs

@@ -281,7 +281,7 @@ impl VM {
                 globals[idx] = val.clone();
                 Ok(val)
             }
-            BoundKind::DefDestructure { pattern, value } => {
+            BoundKind::Destructure { pattern, value } => {
                 let val = self.eval_internal(obs, value)?;
                 let mut offset = 0;
 
@@ -289,7 +289,7 @@ impl VM {
                 if let Some(vals) = val.as_slice() {
                     self.unpack(pattern, vals, &mut offset)?;
                 } else {
-                    self.unpack(pattern, &[val.clone()], &mut offset)?;
+                    self.unpack(pattern, std::slice::from_ref(&val), &mut offset)?;
                 }
                 Ok(val)
             }
@@ -704,6 +704,11 @@ impl VM {
                 globals[idx] = val;
                 Ok(())
             }
+            BoundKind::Set { addr, .. } => {
+                let val = values.get(*offset).cloned().unwrap_or(Value::Void);
+                *offset += 1;
+                self.set_value(*addr, val)
+            }
             BoundKind::Tuple { elements } => {
                 if let Some(sub_values) = values.get(*offset).and_then(|v| v.as_slice()) {
                     *offset += 1;