Is `0x_` valid? about d-grammar HOT 4 CLOSED

(dmd-2.076.1)$ cat lex.d
import std.stdio;

void main()
{
    writeln("0b: ", 0b);
    writeln("0buL: ", 0buL);

    writeln("0x_: ", 0x_);
    writeln("0x: ", 0x);
    writeln("0xuL: ", 0xuL);

    writeln("0_.", 0_.);
    writeln("0_e0: ", 0_e0);
}
(dmd-2.076.1)$ rdmd lex.d
0b: 0
0buL: 0
0x_: 0
0x: 0
0xuL: 0
0_.0
0_e0: 0