syntax_data: {"ast_node_type":"other","tokens":[{"end":58,"kind":"keyword","start":0,"text":"hir::CoroutineSource::Closure,"}]}
source_snippet:                             hir::CoroutineSource::Closure,
context_before:                             hir::CoroutineDesugaring::Async,
context_after:                         ) => write!(self, "async closure")?,