syntax_data: {"ast_node_type":"other","tokens":[{"end":37,"kind":"keyword","start":0,"text":"///"}]}
source_snippet:     /// until we reach a fixed point.
context_before:     /// may cause us to serialize more `SyntaxContext`s, so serialize in a loop
context_after:     latest_ctxts: Lock<FxHashSet<SyntaxContext>>,