Function restrict_capture_precision 

fn restrict_capture_precision(
    place: Place<'_>,
    curr_mode: UpvarCapture,
) -> (Place<'_>, UpvarCapture)

Truncate projections so that the following rules are obeyed by the captured place:

• No Index projections are captured, since arrays are captured completely.
• No unsafe block is required to capture place.

Returns the truncated place and updated capture mode.