Function mode_and_needs_parens_for_adjustment_hints 

fn mode_and_needs_parens_for_adjustment_hints(
    expr: &Expr,
    mode: AdjustmentHintsMode,
) -> (bool, bool, bool)

Returns whatever the hint should be postfix and if we need to add parentheses on the inside and/or outside of expr, if we are going to add (postfix) adjustments hints to it.