[This is preliminary documentation and is subject to change.]
Creates a code expression containing all the text values of an
enum value of an enum type with the [FlagsAttribute] set.
The generated code expression.
For example, if an enum class FlagEnum was defined with the values Flag1, Flag2 and Flag3, and an instance was created with the first and last of these set, then calling with separator " | " with fullyQualified false will produce FlagEnum.Flag1 | FlagEnum.Flag3.