syntax_data: {"ast_node_type":"variable","tokens":[{"end":72,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:         let ty::Dynamic(a_data, a_region, ty::Dyn) = *a_ty.kind() else {
context_after:             bug!("expected `dyn` type in `confirm_trait_upcasting_unsize_candidate`")