syntax_data: {"ast_node_type":"other","tokens":[{"end":91,"kind":"keyword","start":0,"text":"//"}]}
source_snippet: // on stable. Using a feature not on the list of Rust target features only emits a warning.
context_before: // Note that even unstable (and even entirely unlisted) features can be used with `-Ctarget-feature`
context_after: // Only `cfg(target_feature)` and `#[target_feature]` actually do any stability gating.