{"ast_node_type":"other","tokens":[{"end":43,"kind":"keyword","start":0,"text":"///"}]}
    /// fail if the mapping already exists.
    /// Adds a `UniqueTypeId` to metadata mapping to the `TypeMap`. The method will
    pub(super) fn insert(&self, unique_type_id: UniqueTypeId<'tcx>, metadata: &'ll DIType) {