Fix str.__str__

Author: youknowone

vm/src/builtins/str.rs

@@ -364,6 +364,7 @@ impl PyStr {
 #[pyclass(
     flags(BASETYPE),
     with(
+        PyRef,
         AsMapping,
         AsNumber,
         AsSequence,
@@ -481,11 +482,6 @@ impl PyStr {
         Self::repeat(zelf, value.into(), vm)
     }
 
-    #[pymethod(magic)]
-    fn str(zelf: PyRef<Self>) -> PyStrRef {
-        zelf
-    }
-
     #[inline]
     pub(crate) fn repr(&self, vm: &VirtualMachine) -> PyResult<String> {
         rustpython_common::str::repr(self.as_str())
@@ -1270,6 +1266,17 @@ impl PyStr {
     }
 }
 
+#[pyclass]
+impl PyRef<PyStr> {
+    #[pymethod(magic)]
+    fn str(self, vm: &VirtualMachine) -> PyRefExact<PyStr> {
+        self.into_exact_or(&vm.ctx, |zelf| unsafe {
+            // Creating a copy with same kind is safe
+            PyStr::new_str_unchecked(zelf.bytes.to_vec(), zelf.kind.kind()).into_exact_ref(&vm.ctx)
+        })
+    }
+}
+
 impl PyStrRef {
     pub fn concat_in_place(&mut self, other: &str, vm: &VirtualMachine) {
         // TODO: call [A]Rc::get_mut on the str to try to mutate the data in place