syntax_data: {"ast_node_type":"other","tokens":[{"end":78,"kind":"keyword","start":0,"text":"//"}]}
source_snippet:         // Report mutability conflicts for e.g. `ref mut x @ Some(ref mut y)`.
context_before:     if report_mut_mut {
context_after:         sess.dcx().emit_err(MultipleMutBorrows { span: pat.span, occurrences });