syntax_data: {"ast_node_type":"other","tokens":[{"end":77,"kind":"keyword","start":0,"text":"//"}]}
source_snippet:         // Unlike `vreg_index`, we can't subtract `x0` to get the u32 because
context_before:     pub fn reg_index(self) -> Option<u32> {
context_after:         // `x19` and `x29` are missing and the integer constants for the