syntax_data: {"ast_node_type":"function","tokens":[{"end":73,"kind":"keyword","start":0,"text":"fn"}]}
source_snippet:     fn bytepos_to_file_charpos(&self, bpos: RelativeBytePos) -> CharPos {
context_before:     /// Converts an relative `RelativeBytePos` to a `CharPos` relative to the `SourceFile`.
context_after:         // The number of extra bytes due to multibyte chars in the `SourceFile`.