E07300: declaration supporting 'uninitialised' is not needed

What went wrong

You've explicitly declared something as 'uninitialized' where it is not needed. The '?' in 'name as String?' declares a variable WITHOUT a value, so it has no place where a value is always there:

• on a PARAMETER: '-> text as String?' - an incoming parameter always arrives with its argument
• beside a VALUE: 'name as String? : "x"' (or ':=', '=', ':~:') - the declaration gives the variable a value, so the '?' did nothing; it compiled to exactly the code the declaration compiles to without it

Worked examples

Compilable examples demonstrating this error and the correct fix:

• ek9 -q 827 (Why does EK9 reject the ? modifier on function parameters?)

Rationale

EK9 handles uninitialized state through tri-state semantics. A variable declared with 'as TypeName?' starts without a value and the compiler proves it is assigned before use; one declared with a value starts with that value. A '?' that says both is a contradiction a reader cannot resolve - so the compiler does not accept it.

How to fix it

1. Remove the '?': '-> text as String' / 'name as String: "x"'
2. If the variable should really start WITHOUT a value, remove the value instead: 'name as String?'

Common causes

• Over-explicit declarations
• Reading '?' as "nullable", as in Kotlin or C#
• Confusion about initialization rules

See also

• E07300: redundant uninitialized (this error)
• E08070: never initialised in any accessible path
• E01092: '?' on the target of an assignment

Examples

Every example is compiled by the EK9 compiler: the first fails exactly as captioned, the others fix it.

Fails with E07300: declaration supporting 'uninitialised' is not needed

#!ek9
defines module error.e07300.bad

  defines class

    Holder
      prop as String? : "p"

      default operator ?

  defines function

    returnWithAValue()
      <- rtn as String? : String()
      rtn: "x"

    localViaAssign()
      <- rtn as String: String()
      label as String? := "x"
      rtn: label

    localViaEquals()
      <- rtn as String: String()
      label as String? = "x"
      rtn: label

    localViaMerge()
      <- rtn as String: String()
      label as String? :~: "x"
      rtn: label

    //Both forms that ARE meant - a value, or no value yet - stay as they were.
    stillFine()
      <- rtn as String: String()
      label as String: "x"
      pending as String?
      pending: label
      rtn: pending

Fixed: Write '?' only where there is no value yet

#!ek9
defines module error.e07300.good

  defines function

    //A value: no '?'
    withAValue()
      <- rtn as String: "x"

    //No value yet: the '?' says so, and it is assigned later
    noValueYet()
      <- rtn as String: String()
      pending as String?
      pending: "x"
      rtn: pending

Questions and answers

These Q&A entries show E07300 and its fix:

• Q827: Why does EK9 reject the ? modifier on function parameters?