E01020: invalid module name

Category: E01xxx Parsing and excluded constructs · Reported in phase: SYMBOL_DEFINITION · Classification: INVALID_MODULE_NAME · All error codes

What went wrong

The module names of the EK9 core, org.ek9.lang and org.ek9.math, are reserved. User code cannot define a module with either name.

Worked examples

Compilable examples demonstrating this error and the correct fix:

ek9 -q 852 (Which module names are reserved in EK9?)

Reserved names

The rule is EXACT membership, not a prefix:

org.ek9.lang - Core language types (String, Integer, List, etc.)
org.ek9.math - Mathematical types and functions

Other names under org.ek9 (org.ek9.lang.custom, org.ek9.tools) are not reserved by this check - that namespace is where official libraries written in EK9 live.

How to fix it

Choose a different namespace for your module:

Use your organisation's domain (com.mycompany, net.example)
Use a project-specific prefix (myproject.utils)
Any name other than org.ek9.lang and org.ek9.math passes this check

Common causes

Attempting to extend built-in types by adding to reserved namespace
Copy-paste from documentation examples without changing namespace

Note

This restriction is enforced at compile time and cannot be bypassed.

Examples

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

Fails with E01020: invalid module name

#!ek9
defines module org.ek9.lang

  defines function

    helper()
      <- rtn as String: "only the compiler's bootstrap may define this module"

Fixed: Name the module for your own organisation; other org.ek9 names are allowed too

#!ek9
defines module error.e01020.good

  defines function

    helper()
      <- rtn as String: "a module of your own"

Questions and answers

These Q&A entries show E01020 and its fix:

Q852: Which module names are reserved in EK9?