rescript-lang
Support coercing on a function type
I recently discovered that coercion works for variants where everything is represented by the same primitive type: https://rescript-lang.org/docs/manual/latest/variant#coercing-variants-to-primitives
This is great, but I have a function that returns one of these variants and I can't coerce that. It seems to work for no-argument functions, but not functions with arguments. https://rescript-lang.org/try?version=v11.1.1&code=C4TwDgpgBAhgzgSQHbCgXigHygAXgCgEYBKKAeSWmzznwCZSAVAdwHstcCBmJgCwCcIEAFDCANhFStKyYAC5YiFOnKVxkqMFayV+aRB1yAfFACWKYqImpBwAK78ksgKpJTqDPlJoTFEdahbBycUAGVzAHMJXQB9b181dVQtWQAxQl0gxxc3VGMofDtc9BNzYGJLAJSUVLpMyWDZcKQo6Hz8AHIYErMLYiA
The specific example I'm trying to model is array sort, so I'd need it to work on 2-argument functions as well. https://rescript-lang.org/try?version=v11.1.1&code=C4TwDgpgBAxg9gWzAQwE4EsDOcB2UC8AUFFAD5QACymAFALQCMAlFADISaYAqAFsjsTKVqNAAwsAogEcArsgA2g8lVrMoAcVQRkwCKl79ChOJDwApTADoAgqlTIQAJkLyIwKNlTv8UGmlQANFAAfgBmAFy+AOTIQTEs+AB8sIgoGNg4CYmCnsAAkjgACvLIMBAA6ujAPH52dImY8uhlAGKoiGJMQTShUOHJ6DjATExAA
One observation: the coercion in the example seems to work if the argument type is not polymorphic, e.g. float.
Coercion was not modified for function types, it still uses the original implementation, but the way it's been implemented for variants might interfere with the pre-existing mechanism in certain cases (e.g. polymorphic argument).
Ah, that makes sense. Unfortunately the way I'm trying to use it with Array sort requires polymorphism.
For now I've just used an obj magic.
@TheSpyder any more tests for https://github.com/rescript-lang/rescript-compiler/pull/6828 ?
@cristianoc the second example is the one I pulled from my codebase, I haven't come across any others (although I haven't really been looking). I appreciate you looking at this!
@cristianoc the second example is the one I pulled from my codebase, I haven't come across any others (although I haven't really been looking). I appreciate you looking at this!
Great, that example is covered already.