{"ast_node_type":"variable","tokens":[{"end":65,"kind":"keyword","start":0,"text":"let"}]}
    let const_ty = ecx.ty(sig_span, TyKind::Tup(ThinVec::new()));
    // Generate anonymous constant serving as container for the allocator methods.
    let const_body = ecx.expr_block(ecx.block(span, stmts));