syntax_data: {"ast_node_type":"other","tokens":[{"end":97,"kind":"keyword","start":0,"text":"///"}]}
source_snippet:     /// `pad_i32` indicates if a `Reg::i32()` dummy argument is emitted before the real argument.
context_before:     ///
context_after:     Cast { pad_i32: bool, cast: Box<CastTarget> },