Function translate_constant_reference 

pub fn translate_constant_reference<'tcx>(
    s: &impl UnderOwnerState<'tcx>,
    span: Span,
    ucv: UnevaluatedConst<'tcx>,
) -> Option<ConstantExpr>

Attempts to translate a ty::UnevaluatedConst into a constant expression. This handles cases of references to top-level or associated constants. Returns None if the input was not a named constant.