syntax_data: {"ast_node_type":"other","tokens":[{"end":73,"kind":"keyword","start":0,"text":"//"}]}
source_snippet:                     // Generate the implicit `else {}` by assigning unit.
context_before:                     // There is no `else` arm, so we know both arms have type `()`.
context_after:                     let correct_si = this.source_info(expr_span.shrink_to_hi());