Function rustc_query_impl::make_query::opt_const_param_of

pub fn opt_const_param_of<'tcx>(
    tcx: QueryCtxt<'tcx>, 
    key: opt_const_param_of<'tcx>
) -> QueryStackFrame

Computes the DefId of the corresponding const parameter in case the key is a const argument and returns None otherwise.

let a = foo::<7>();
//            ^ Calling `opt_const_param_of` for this argument,

fn foo<const N: usize>()
//           ^ returns this `DefId`.

fn bar() {
// ^ While calling `opt_const_param_of` for other bodies returns `None`.
}