syntax_data: {"ast_node_type":"variable","tokens":[{"end":48,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:     let source_info = builder.source_info(span);
context_before:         region::Scope { local_id: body.id().hir_id.local_id, data: region::ScopeData::Arguments };
context_after:     let call_site_s = (call_site_scope, source_info);