syntax_data: {"ast_node_type":"other","tokens":[{"end":46,"kind":"keyword","start":0,"text":"_target:"}]}
source_snippet:                 _target: &crate::spec::Target,
context_before:                 _target_features: &rustc_data_structures::fx::FxIndexSet<Symbol>,
context_after:                 _is_clobber: bool,