fix event control asterisk to accept whitespace between @ and *

[yousifBilal]

This is a fix for EventControlAsterisk to have 2 symbols @ and *. Most compilers seems to accept a whitespace between @ and *. This module was not being parsed with sv-parser. While others like https://sv-lang.com/explore/ and verilator considered it valid.

module test;
    reg a, b;
    reg out; 

    always @ * begin
        out = a & b;
    end

    always @* begin
        out = a | b;
    end
    initial begin
        // Initialize inputs
        a = 0; b = 0;
        #10; a = 1; b = 0;
        #10; a = 0; b = 1;
        #10; a = 1; b = 1;
        #10; $finish;
    end

    initial begin
        $monitor("At time %0t: a = %0b, b = %0b, out = %0b", $time, a, b, out);
    end
endmodule

[dalance]

Thank you for your contribution.
This seems to be difficult problem.

According to IEEE1800-2017, the definition of event_control is below.
It shows space between @ and * is not allowed.

event_control ::=
@ hierarchical_event_identifier
| @ ( event_expression )
| @*
| @ (*)
| @ ps_or_hierarchical_sequence_identifier

Actually, the following code causes syntax error by Synopsys VCS.
We can't request to fix it because it seems to be forbidden by language specification.

always @ /* comment */ * begin
    out = a & b;
end

On the other hand, IEEE1800-2023 is below.
It shows space is allowed.

event_control ::=
clocking_event
| @ *
| @ ( * )

So I think the current behaviour should be kept at least to check IEEE1800-2017 compliant.
And "IEEE1800-2023 mode" which accepts the space is probably required too.

[yousifBilal]

How would realize a "IEEE1800-2023 mode"? would you do it as part of this project or a separate one dedicated for 2023?

[dalance]

I don't have enough motivation to create individual project for 2023.
So I'll consider about adding mode switch in this project.

[ethanuppal]

Could you use Cargo features?