syntax_data: {"ast_node_type":"other","tokens":[{"end":48,"kind":"keyword","start":0,"text":"impl_def_id.to_def_id(),"}]}
source_snippet:                         impl_def_id.to_def_id(),
context_before:                         tcx,
context_after:                         tcx.impl_trait_ref(impl_def_id).unwrap().instantiate_identity().args,