fix pattern aliases for strings when targeting erlang

[wgancar]

Hello, this is my attempt to fix the issue described here

#2733

Currently making aliases for string patterns doesn't work when complied to erlang. The problem is that erlang doesn't allow aliases for constant binary patterns.

My workaround is to match the number of bytes first and then write additional guard to check if matched bytes matches the provided pattern

so that this

case x {
  "Hello, " as greeting <> name  -> greeting
}

becomes this

<<Greeting:7/binary, Name/binary>> when Greeting =:= <<"Hello, ">> ->
            Greeting;

instead of invalid code that we have today

<<"Hello, "/utf8 = Greeting, Name/binary>> ->
            Greeting;

If this is acceptable approach I still have one issue to fix, If there are some user defined guards on the clause level I have to replace when with andalso to make sure that both guards are supported

[lpil]

The approach looks great to me! We do something similar to this on JavaScript. Let me know when you would like a code review, thank you.

[wgancar]

Ok, I think im ready for review. Ive made sure that user defined guards are working properly and I've added test to verify that

[lpil]

Thank you but we cannot introspect the algebra to learn things about the code. The code is source of information here.

Could you also add comments like the ones you removed please 🙏

[lpil]

Remove this please, it's not appropriate to introspect the printing alegbra, and this isn't a correct implementation as it could be across multiple variants.

[wgancar]

You are absolutely right, sorry

[wgancar]

Thank you but we cannot introspect the algebra to learn things about the code. The code is source of information here.

Could you also add comments like the ones you removed please 🙏

Thank you for the review I appreciate it a lot 💜 Im still not sure where this guard check should happen. Right now I made simple function in patterns module but Im not sure if its feels right. Any suggestions?

[lpil]

Beautiful work! Thank you very much! 💜