Unable to use literal astral-plane unicode character in identifier in JavaScript

[Claude Pache]

Type:

    var 𐋀;

where the character before the semi-colon is U+102C0 (CARIAN LETTER G).

Equivalently, try:

    eval("var \u{102C0};"); // (note that the escape sequence is expanded when evaluating the string)

I get the error:

    SyntaxError: Invalid character '\u55296'

I expect: no error (because U+102C0 is a letter).

Note that the following code works as expected (no error):

    var \u{102C0};

[Claude Pache]

Maybe related: Bug 121541

[Alexey Proskuryakov]

Seems very basic, but I can't remember this come up before. Very surprising.