verilator/test_regress/t/t_sampled_expr_unsup.v

// DESCRIPTION: Verilator: Verilog Test module
//
// This file ONLY is placed under the Creative Commons Public Domain.
// SPDX-FileCopyrightText: 2022 Antmicro Ltd
// SPDX-License-Identifier: CC0-1.0

module t (
    input clk
);

  int a = 0;

  function int f(output int a);
    a = 1;
    return a;
  endfunction

  assert property (@(posedge clk) f(a) >= 0);
endmodule