syntax_data: {"ast_node_type":"other","tokens":[{"end":91,"kind":"keyword","start":0,"text":"///"}]}
source_snippet:     /// lowered, with the span where it was introduced. `None` for a by-value default mode.
context_before:     /// Internal state: the ref-mutability of the default binding mode at the subpattern being
context_after:     default_mode_span: Option<(Span, ty::Mutability)>,