What are the most common EK9 compiler errors and what do they mean?

← Debugging and Troubleshooting · Ref: Q983

The most common EK9 compiler errors:

E50001 NOT RESOLVED — a name (variable, type, or function) cannot be found. Likely a typo, missing import, or using := before <- to declare.

E50060 METHOD NOT RESOLVED — calling a method that does not exist on the type. Check the type API with 'ek9 -h TypeName'.

E05030 NOT OPEN TO EXTENSION — trying to extend a class that is closed by default. Add 'as open' to the base class or use composition.

E01072 RETURN NOT SUPPORTED — using 'return' which does not exist in EK9. Declare return variable with <- and the compiler ensures all paths initialise it.

E01073 NULL NOT SUPPORTED — using 'null' which does not exist in EK9. Use tri-state semantics with ? operator to check if a value is set.

E11031 NON DESCRIPTIVE NAME — using a banned variable name like 'temp', 'data', 'flag'. Use a descriptive name instead.

E08030 UNSAFE ACCESS — accessing a value that might be unset without checking first. Use a guard 'if v <- expr()' or check with v? before access.

Use 'ek9 -h Exxxxx' for detailed explanation of any error code.

Example

defines module qa.debugging.commonerrors

  defines function

    safeDivide() as pure
      ->
        numerator as Float
        denominator as Float
      <- rtn as Float: Float()

      if denominator?
        rtn: numerator / denominator

  defines program

    CommonErrorsDemo()
      stdout <- Stdout()

      // Correct: <- to declare, := to update
      greeting <- "Hello"
      greeting := "Hi there"
      stdout.println(greeting)

      // Correct: ? to check before use
      answer <- safeDivide(10.0, 3.0)
      if answer?
        stdout.println(`Result: ${answer}`)

      // Correct: guard instead of null check
      if safeAnswer <- safeDivide(10.0, 0.0)
        stdout.println(`Got: ${safeAnswer}`)
      else
        stdout.println("Division returned unset")

Common mistakes

E50001 — E50001 means the name is not resolved. If you used := before <-, the variable does not exist yet. Use <- to declare it first.

Incorrect:

      greeting := "Hello"

Correct:

      greeting <- "Hello"

Coming from another language?

Java developers most often hit E05030 (closed types) and E01072 (no return). Python developers hit E50001 (typos) and E11031 (banned names). All hit E01073 (no null) initially.

Keywords: error, common, troubleshoot, E05030, debug, E50060, E50001