Function rustc_middle::middle::lang_items::required

pub fn required(tcx: TyCtxt<'_>, lang_item: LangItem) -> bool

Returns true if the specified lang_item must be present for this compilation.

Not all lang items are always required for each compilation, particularly in the case of panic=abort. In these situations some lang items are injected by crates and don’t actually need to be defined in libstd.