syntax_data: {"ast_node_type":"other","tokens":[{"end":40,"kind":"keyword","start":0,"text":".collect::<Result<_,"}]}
source_snippet:             .collect::<Result<_, _>>()?,
context_before:             .map(|(i, ty)| arg_of(ty, Some(i)))
context_after:         c_variadic: sig.c_variadic,