E08140: component injection not allowed when scope is marked as 'pure'

What went wrong

You're trying to inject a COMPONENT inside a PURE context. Component injection is an impure operation (it involves runtime state).

Worked examples

Compilable examples demonstrating this error and the correct fix:

• ek9 -q 666 (Why can't I inject components in a pure context?)

Rationale

Components represent stateful resources - not compatible with purity.

How to fix it

1. Inject at field level instead of inside pure method
2. Pass required data as parameters to pure method
3. Remove 'pure' if component access needed

Common causes

• Component injection in pure method
• Pure function trying to access services

See also

• E08140: injection in pure context (this error)
• E08150: injecting concrete component

Examples

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

Fails with E08140: component injection not allowed when scope is marked as 'pure'

#!ek9
defines module error.e08140.bad

  defines function

    stamp() as pure
      <- rtn as String?
      timekeeper as Timekeeper!
      rtn: timekeeper.now()

  defines component

    Timekeeper as abstract
      now() as pure abstract
        <- rtn as String?

Fixed: Inject only where the scope is not pure

#!ek9
defines module error.e08140.good

  defines function

    stamp()
      <- rtn as String?
      timekeeper as Timekeeper!
      rtn: timekeeper.now()

  defines component

    Timekeeper as abstract
      now() as pure abstract
        <- rtn as String?

Fixed: Or keep the function pure and pass the component in

#!ek9
defines module error.e08140.good.parameter

  defines component

    Timekeeper as abstract
      now() as pure abstract
        <- rtn as String?

  defines function

    stamp() as pure
      -> timekeeper as Timekeeper
      <- rtn as String: timekeeper.now()

Questions and answers

These Q&A entries show E08140 and its fix:

• Q666: Why can't I inject components in a pure context?