Function rustc_typeck::collect::is_param

pub(in collect) fn is_param(
    tcx: TyCtxt<'_>, 
    ast_ty: &Ty<'_>, 
    param_id: HirId
) -> bool

Tests whether this is the AST for a reference to the type parameter with ID param_id. We use this so as to avoid running ast_ty_to_ty, because we want to avoid triggering an all-out conversion of the type to avoid inducing unnecessary cycles.