isIdentChar function
True if codeUnit is an ASCII identifier continuation character.
Shared with TokenGuard.wordBoundary and kept here so the interpreter doesn't need to duplicate the class definition.
Implementation
bool isIdentChar(int codeUnit) =>
(codeUnit >= 0x30 && codeUnit <= 0x39) || // 0-9
(codeUnit >= 0x41 && codeUnit <= 0x5A) || // A-Z
(codeUnit >= 0x61 && codeUnit <= 0x7A) || // a-z
codeUnit == 0x5F;