syntax_data: {"ast_node_type":"variable","tokens":[{"end":48,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:         let pat = self.lower_pattern(&cx, pat)?;
context_before:         let cx = self.new_cx(refutability, None, scrut, pat.span);
context_after:         let arms = [MatchArm { pat, arm_data: self.lint_level, has_guard: false }];