syntax_data: {"ast_node_type":"other","tokens":[{"end":55,"kind":"keyword","start":0,"text":"///"}]}
source_snippet:     /// items can be used (that is, a macro marked with
context_before:     /// Checks if a span is "internal" to a macro in which `#[unstable]`
context_after:     /// `#[allow_internal_unstable]`).