syntax_data: {"ast_node_type":"function","tokens":[{"end":53,"kind":"keyword","start":0,"text":"fn"}]}
source_snippet:     fn from_str(s: &str) -> Result<Self, Self::Err> {
context_before:     type Err = String;
context_after:         rustc_abi::Endian::from_str(s).map(Self)