unison/unison-src/transcripts/fix1800.output.md

printLine : Text ->{IO} ()
printLine msg =
  _ = putBytes.impl (stdHandle StdOut) (Text.toUtf8 (msg ++ "\n"))
  ()

-- An unannotated main function
main1 = '(printLine "\nhello world!")

-- Another variation
main2 _ = printLine "🌹"

-- An annotated main function
main3 : '{IO} ()
main3 _ = printLine "🦄 ☁️  🌈"

Testing a few variations here:

• Should be able to run annotated and unannotated main functions in the current file.
• Should be able to run annotated and unannotated main functions from the codebase.

.> run main1

  ()

.> run main2

  ()

.> run main3

  ()

.> add

  ⍟ I've added these definitions:
  
    main1     : '{IO} ()
    main2     : ∀ _. _ ->{IO} ()
    main3     : '{IO} ()
    printLine : Text ->{IO} ()

.> rename.term main1 code.main1

  Done.

.> rename.term main2 code.main2

  Done.

.> rename.term main3 code.main3

  Done.

The renaming just ensures that when running code.main1, it has to get that main from the codebase rather than the scratch file:

.> run code.main1

  ()

.> run code.main2

  ()

.> run code.main3

  ()

Now testing a few variations that should NOT typecheck.

main4 : Nat ->{IO} Nat
main4 n = n

main5 : Nat ->{IO} ()
main5 _ = ()

This shouldn't work since main4 and main5 don't have the right type.

.> run main4

  😶
  
  I found this function:
  
    main4 : Nat ->{IO} Nat
  
  but in order for me to `run` it needs to be a subtype of:
  
    main4 : '{IO, Exception} result

.> run main5

  😶
  
  I found this function:
  
    main5 : Nat ->{IO} ()
  
  but in order for me to `run` it needs to be a subtype of:
  
    main5 : '{IO, Exception} result