syntax_data: {"ast_node_type":"other","tokens":[{"end":77,"kind":"keyword","start":0,"text":"///"}]}
source_snippet: /// type parameters of the two impls. Here the `source_impl` is the one we've
context_before: /// a parent impl providing a default, we need a way to translate between the
context_after: /// selected, and `source_args` is its generic parameters.