syntax_data: {"ast_node_type":"other","tokens":[{"end":30,"kind":"keyword","start":0,"text":".map(|arg|"}]}
source_snippet:                     .map(|arg|
context_before:                     .iter()
context_after:                         Ok(Spanned { node: self.parse_operand(*arg)?, span: self.thir.exprs[*arg].span  } )