https://issues.dlang.org/show_bug.cgi?id=19246

          Issue ID: 19246
           Summary: invalid binary literal `0b_` allowed
           Product: D
           Version: D2
          Hardware: x86
                OS: Mac OS X
            Status: NEW
          Severity: enhancement
          Priority: P1
         Component: dmd
          Assignee: nobody@puremagic.com
          Reporter: schveiguy@yahoo.com

In issue 19018, the literals `0x`, `0x_`, and `0b` were deprecated. However, `0b_` was left as a valid literal.

I can't see a good reason to allow this as a literal.

Note that the current compiler implements exactly what is in the spec, but the spec seems inconsistent to me.

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