INIT of LUT1 must be 2 bit ?

[lehaifeng000]

Version

0.47

On which OS did this happen?

Linux

Reproduction Steps

top.v

module top(
    output  led 
);
    LUT1 #(
        .INIT(1'b1)
    ) lut1_inst (
        .I0(1'b1),
        .O(led)
    );

endmodule

command: yosys -p "synth_xilinx -flatten -nowidelut -arch xc7 -top top; json -o synth.json top;" top.v

Expected Behavior

synth pass

Actual Behavior

2.49. Executing OPT_LUT_INS pass (discard unused LUT inputs).
terminate called after throwing an instance of 'std::out_of_range'
what(): vector::_M_range_check: __n (which is 1) >= this->size() (which is 1)

[lehaifeng000]

if the INIT is set .INIT(2'b1), it will pass