syntax_data: {"ast_node_type":"variable","tokens":[{"end":66,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:                 let cast_kind = mir_cast_kind(source_ty, expr.ty);
context_before:                 let source_ty = source.ty(self.body.local_decls(), self.tcx);
context_after:                 Ok(Rvalue::Cast(cast_kind, source, expr.ty))