syntax_data: {"ast_node_type":"variable","tokens":[{"end":42,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:                     let annotation_index =
context_before:                     let ty_source_info = this.source_info(user_ty_span);
context_after:                         this.canonical_user_type_annotations.push(CanonicalUserTypeAnnotation {