syntax_data: {"ast_node_type":"other","tokens":[{"end":72,"kind":"keyword","start":0,"text":"///"}]}
source_snippet:     /// actually declared. This is called a **placeholder** type, and we
context_before:     /// kind of "fresh" type that is distinct from all other types we have
context_after:     /// use universes to talk about this. In other words, a type name in