syntax_data: {"ast_node_type":"other","tokens":[{"end":77,"kind":"keyword","start":0,"text":"field:"}]}
source_snippet:                         field: self.typeck_results.field_index(field.hir_id),
context_before:                     .map(|field| FieldPat {
context_after:                         pattern: *self.lower_pattern(field.pat),