Function truncate_place_to_len_and_update_capture_kind 

fn truncate_place_to_len_and_update_capture_kind<'tcx>(
    place: &mut Place<'tcx>,
    curr_mode: &mut UpvarCapture,
    len: usize,
)

Truncates place to have up to len projections. curr_mode is the current required capture kind for the place. Returns the truncated place and the updated required capture kind.

Note: Capture kind changes from MutBorrow to UniqueImmBorrow if the truncated part of the place contained Deref of &mut.