syntax_data: {"ast_node_type":"other","tokens":[{"end":113,"kind":"keyword","start":0,"text":"//"}]}
source_snippet:                 // We already checked the compatibility of auto traits within `assemble_candidates_for_unsizing`.
context_before:                 // See `assemble_candidates_for_unsizing` for more info.
context_after:                 let existential_predicates = if data_b.principal().is_some() {