syntax_data: {"ast_node_type":"other","tokens":[{"end":77,"kind":"keyword","start":0,"text":"///"}]}
source_snippet:     /// to prove that the source type upholds all of the target type's object
context_before:     /// alias bound or projection predicate. For trait upcasting, this is used
context_after:     /// bounds. For object type bounds, this is used when eagerly replacing