{"ast_node_type":"other","tokens":[{"end":34,"kind":"keyword","start":0,"text":"substitution:"}]}
            substitution: FnSubst(
            sig: FnSig { abi: FnAbi::RustCall, safety: chalk_ir::Safety::Safe, variadic: false },
                Substitution::from_iter(Interner, sig_tys.iter().cloned()).shifted_in(Interner),