syntax_data: {"ast_node_type":"other","tokens":[{"end":62,"kind":"keyword","start":0,"text":"//"}]}
source_snippet:             // it can be reinstated when we leave the pattern.
context_before:             // This changes the default binding mode to `ref` or `ref mut`. Return the old mode so
context_after:             self.default_mode_span.replace((pat_span, min_mutbl))