{"ast_node_type":"variable","tokens":[{"end":83,"kind":"keyword","start":0,"text":"let"}]}
        let sig = match (self.merged_ty().kind(Interner), expr_ty.kind(Interner)) {
        // https://github.com/rust-lang/rust/blob/7b805396bf46dce972692a6846ce2ad8481c5f85/src/librustc_typeck/check/coercion.rs#L877-L916
            (TyKind::FnDef(x, _), TyKind::FnDef(y, _))