syntax_data: {"ast_node_type":"other","tokens":[{"end":67,"kind":"keyword","start":0,"text":"guard:"}]}
source_snippet:             guard: arm.guard.as_ref().map(|g| self.mirror_expr(g)),
context_before:             pattern: self.pattern_from_hir(&arm.pat),
context_after:             body: self.mirror_expr(arm.body),