syntax_data: {"ast_node_type":"other","tokens":[{"end":68,"kind":"keyword","start":0,"text":"(\"flagm2\","}]}
source_snippet:     ("flagm2", Unstable(sym::aarch64_unstable_target_feature), &[]),
context_before:     // FEAT_FLAGM2
context_after:     // We forbid directly toggling just `fp-armv8`; it must be toggled with `neon`.