[Issue 23376] New: Allow multi-code-point HTML entities

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=23376

          Issue ID: 23376
           Summary: Allow multi-code-point HTML entities
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P1
         Component: dmd
          Assignee: nobody at puremagic.com
          Reporter: qs.il.paperinik at gmail.com

On https://dlang.org/spec/entity.html it says:
> The full list of named character entities from the HTML 5 Spec is supported except for the named entities which contain multiple code points.

This exception seems like an arbitrary limitation. It might make the
implementation easier, but could surprise users.

Even if this enhancement is rejected, the compiler should at least recognize
HTML5 multi-code-point entities and emit a specific error, something like:
“character entity ∾̳ specifies multiple code points (U+223E, U+0333) which
is not supported. Use \u223E\u0333 instead.”

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