unison/unison-src/transcripts/fix1800.md

.> builtins.mergeio

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
.> rename.term main1 code.main1
.> rename.term main2 code.main2
.> rename.term main3 code.main3

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

.> run main5