[Issue 22543] New: [spec] grammar blocks use unspecified notation

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=22543

          Issue ID: 22543
           Summary: [spec] grammar blocks use unspecified notation
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: normal
          Priority: P1
         Component: dlang.org
          Assignee: nobody at puremagic.com
          Reporter: dkorpel at live.nl

Newsgroup discussion:
https://forum.dlang.org/post/gwcvsqctgsuetdyfenyz@forum.dlang.org

Blocks like:
```
SpecialTokenSequence:
    # line IntegerLiteral Filespecopt EndOfLine
    # line __LINE__ Filespecopt EndOfLine
```

```
ByteOrderMark:
    \uFEFF

Shebang:
    #! Charactersopt EndOfShebang

EndOfShebang:
    \u000A
    EndOfFile
```

Have a certain meaning:
- an identifier with a colon denotes a rule
- the following lines denote alternatives
- spaces between elements of a rule denote either immediate concatenation
(lexical grammar), or optional separation by Comments and WhiteSpace (parsing
grammar)
- the 'opt' suffix means 'optional'
- text in boldface denotes a string / character literal (lexical grammar) or
single token (parsing grammar)

But none of this is specified.

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