syntax_data: {"ast_node_type":"other","tokens":[{"end":51,"kind":"keyword","start":0,"text":"//"}]}
source_snippet:             // unreachable (except via false edge).
context_before:             // This arm has a dummy body, we don't need to generate code for it. `block` is already
context_after:             let source_info = self.source_info(sub_branch.span);