syntax_data: {"ast_node_type":"variable","tokens":[{"end":78,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:                 let existential_predicates = if data_b.principal().is_some() {
context_before:                 // We already checked the compatibility of auto traits within `assemble_candidates_for_unsizing`.
context_after:                     tcx.mk_poly_existential_predicates_from_iter(