Dynamic import doesn't work with `external` that defines a function

[anmonteiro]

#6663 fixed an issue where @module("..") external .. would also emit a static import. But it looks like external + dynamic import isn't very well supported if the external is an arrow. Here's a playground link.

Wondering if that's on purpose or an oversight. Obviously you can extract the arrow to type f = string => unit or something along those lines, but that disables a few optimizations and you can't use attributes such as @unwrap and friends.

[anmonteiro]

I guess this is what has been described as a limitation in #6664 (comment)

[mununki]

I guess this is what has been described as a limitation in #6664 (comment)

Thanks for refreshing my memory. You're right, it's something we didn't implement due to the limitations of our implementation at the time.

[anmonteiro]

@mununki to fix this, you can probably attach an attribute to the primitive translation here:

https://github.com/rescript-lang/rescript-compiler/blob/30b38a0aaab27ad4c99f34037b1cc4d61589da8e/jscomp/ml/translcore.ml#L504-L510

that you then use when compiling the lambda