JS/Node codegen for Stream cause error

[luochen1990]

Steps to Reproduce

the file bug1.idr:

symbols : Stream Char
symbols = cycle (unpack "abc")

main : IO ()
main = do
    print $ take 10 symbols

and the command:

$ idris --codegen node bug1.idr -o bug1.js
idris: Can't happen pickAlt - impossible case found
CallStack (from HasCallStack):
  error, called at src\IRTS\LangOpts.hs:241:25 in idris-1.3.0-CM7OgpWXYDl5DkSeW84F9Q:IRTS.LangOpts

Expected Behavior

Compiles successfully.

Observed Behavior

Compiles failed.

[jfdm]

@luochen1990

In case you were not aware, IO is short hand for IO' FFI_C, and as such IO is only for use with the C codegen. For other backends, i.e. JS, there should be an equivalent IO' FFI_JS instances.

Thus, what you are experiencing is expected behaviour. However, the error message could be made better, as it is not clear (from the message) why Idris itself is failing.

Jan

[luochen1990]

@jfdm thanks for your explanation, but the IO and JS_IO problem seems not explain everything, consider the following test:

symbols : Stream Char
symbols = cycle (unpack "abc")

symbols2 : Stream Char
symbols2 = cycle ['a', 'b', 'c']

symbols3 : List Char
symbols3 = unpack "abc"

main : IO ()
main = do
    print $ take 10 symbols3

when I use symbols3, it works correctly and the correct js file is generated. and things works well on symbols2 too, but for symbols it is just not working. it seems weird for me, and I thought there must be something wrong when we use Stream and unpack and js codegen together.