Computed value

[Jack-Works]

Should the value be an expression instead of a literal?

enum Computed {
    A = expr(),
}

Computed value, but restricted

The computed value is very useful when we want to support the bit-flag enum.

enum FileAccess {
  None = 0,
  Read = 1 << 1,
  Write = 1 << 2,
  ReadWrite = Read | Write,
}

We can limit the ability of computed value to only allows the following on the RHS:

• string, number, bigint literal
• Unary - operator (to allow negative number)
• Unary ~ operator (bit-flag)
• Binary | & << >> >>>, ^ operator (bit-flag)
• Enum member reference that previously defined in the current enum (differ than TypeScript which allows access of different enum).
• (expr) to allow specify the priority of computation

Problem

The full dynamic computed property value conflicts with inline-able (#4) and hoistable declaration (#18).

The limited version conflicts with Heterogeneous Enum (#8) because you cannot declare an enum member should be a symbol. unless we have some ad-hoc syntax for it.

[ljharb]

Why would this be restricted? Values must be able to be symbols, first of all, and i consider #8 to be a requirement.

[Jack-Works]

This feature conflicts with the statically analyzable requirement (#4). If we give up this requirement, we can have this feature and #8.