syntax_data: {"ast_node_type":"variable","tokens":[{"end":33,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:                 let parent_args =
context_before:                 let typeck_root_def_id = tcx.typeck_root_def_id(did);
context_after:                     tcx.erase_regions(GenericArgs::identity_for_item(tcx, typeck_root_def_id));