message: Impl Display for MutableList
  Summary: For consistency.
diff: @@ -284,6 +284,12 @@ impl<'v> Display for List<'v> {
  }
  }
  +impl<'v> Display for MutableList<'v> {
  + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  + display_list(&self.0.borrow().content, f)
  + }
  +}
  +
  impl Display for FrozenList {
  fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  display_list(coerce_ref(&self.content), f)
  @@ -337,9 +343,9 @@ impl<'v> ListLike<'v> for FrozenList {
  }
  }
  -impl<'v, T: ListLike<'v>> Display for ListGen<T> {
  +impl<T: Display> Display for ListGen<T> {
  fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  - display_list(&*self.0.content(), f)
  + Display::fmt(&self.0, f)
  }
  }
  @@ -356,7 +362,7 @@ fn display_list(xs: &[Value], f: &mut fmt::Formatter<'_>) -> fmt::Result {
  impl<'v, T: ListLike<'v>> StarlarkValue<'v> for ListGen<T>
  where
  - Self: AnyLifetime<'v>,
  + Self: AnyLifetime<'v> + Display,
  {
  starlark_type!(List::TYPE);
  