crystal-lang/crystal

The Crystal programming language | http://crystal-lang.org | Fund Crystal's development: http://is.gd/X7PRtI | Docs: http://crystal-lang.org/docs/ | API: http://crystal-lang.org/api/

didactic-drunk

@didactic-drunk

I guess that wasn't a shortened answer

ryanprior

@ryanprior:matrix.org

[m]

I'm having trouble casting a type to a more permissive type. For example, suppose I define my type as:

alias PermissiveType = Array(String | Int32) | String
s : PermissiveType = "hello world" #works
ss : PermissiveType = ["hello", "world"] # must be (Array(Int32 | String) | String), not Array(String)

It seems like since PermissiveType is strictly more permissive than Array(String) this cast should be possible - any possible value of that more restrictive type should satisfy the more permissive type.

How do I accomplish that?

Kirk Haines

@wyhaines

@ryanprior:matrix.org What you are running into is that while one can logically look at an Array(String) and see that an Array(String | Int32) can store everything in it, type specifications are very specific, and your type specification is for two things, either an Array(String | Int32), or String, and what you are trying to assign is an Array(String), which is not either of those things.

ss : PermissiveType = Array(String | Int32).new + ["hello", "world"]

That will create an array with a type signature that matches what PermissiveType allows.

Ali Naqvi

@naqvis

^ or provide the type of literal
ss : PermissiveType = ["hello", "world"] of String | Int32

if yo don't provide the type, compiler will infer that as Array(String)

Kirk Haines

@wyhaines

Thanks. My daughter interrupted me to move the van, and you finished for me. :)

Ali Naqvi

@naqvis

Kirk Haines

@wyhaines

@ryanprior:matrix.org are you the current maintainer of crystal-readline? I have a private fork of it that I have been forced to maintain because the mainline lacks proper Crystal 1.0+ support. If I provide a PR, can we get the mainline project updated and a new release built?

ryanprior

@ryanprior:matrix.org

[m]

I'm not the maintainer but that would be useful for me too

Kirk Haines

@wyhaines

OK. I saw a commit from you on the main repo, so I was wondering.

Holden Omans

@kalinon

Anyone know how to build with -Dpreview_mt in the alpine-build docker image?

George Dietrich

@Blacksmoke16

try in the nightly image

3 replies

crystal-lang/distribution-scripts#63 was merged recently but not sure if it's actually in the nightly image atm or if there's another step that needs done to enable it

Holden Omans

@kalinon

oh nice ill try it out

didactic-drunk

@didactic-drunk

Is there a macro or easy way I can store the caller of .newfor reference later in finalize to track potential API misuse? I would prefer easy single line way to add this to any class

Kirk Haines

@wyhaines

@didactic-drunk that complete functionality doesn't exist so far as I am aware, but all of the building blocks exist. Maybe it can be my macro-hacking project of the week to build it.

Right now I am picturing something such as simple as include CallTrace, followed by an annotation on top of any method that one want's to build a call tracing stack for.

The actual call trace would be accessible at any time.

Jonathan Silverman

@mixflame

hello guys... this code pings out on Rizon (Ping Timeout) after it joins the #8chan channel... I asked in #Help on Rizon but I'll post the code here in case anyone wants to try to find the issue.... it has to do with the level of chatting... I suspect I need a "spawn" somewhere. https://gist.github.com/mixflame/e4bc13dd5d9a73af1524b2fe52c430a6

note that rizon is a custom network with special requirements that other networks don't possess.... like pinging on connect... might look wrong for other networks or just be fine... not sure about IRC internals as much as others might be

if you want to use it to build a bot, go ahead, it's based on the irc lib for crystal on github

be aware of the ping issue and if you find a solution let me know

Matthew Berry

@mattrberry

How do you properly case over a runtime type of an object? https://carc.in/#/r/bc3v

George Dietrich

@Blacksmoke16

https://carc.in/#/r/bc3w

Matthew Berry

@mattrberry

Thank you

I feel like mine should still work though

Or am I misunderstanding something?
(sorry for sending 4 messages when I could have sent 1 lol)

Also as a side note, I feel like we shouldn't need to include A as one of the branches of the case since it cannot have an instantiation at runtime

Quinton Miller

@HertzDevil

crystal-lang/crystal#9116

George Dietrich

@Blacksmoke16

Is nothing preventing you or someone else to extend it and break it

Quinton Miller

@HertzDevil

well you definitely cannot omit A.class for the original snippet because A is indeed an instantiation of A.class

Matthew Berry

@mattrberry

Ah, gotcha

If I wanted to check the runtime type of an object in my example there, but I defined === on A, how would I go about doing that? Or would I just have to use a conditional expression to check the class?

George Dietrich

@Blacksmoke16

sure you want === and not ==?

Matthew Berry

@mattrberry

I don't actually have a use-case for it

I'm just wondering

George Dietrich

@Blacksmoke16

=== should only be needed if you need custom case equality logic

it might just work tbh, like see the the when value is a type as the compiler expands it to is_a?

Matthew Berry

@mattrberry

Oh does the compiler special-case that?

George Dietrich

@Blacksmoke16

i think so yea

be easy enough to try

Matthew Berry

@mattrberry

Yeah seems like it does

Only other thing then would be that this should technically be able to compile I believe, since foo.is_a? cannot be an A, right? https://carc.in/#/r/bc45

Quinton Miller

@HertzDevil

that's what that rfc discusses

Matthew Berry

@mattrberry

Ah gotcha, thank you

George Dietrich

@Blacksmoke16

well technically foo.is_a? A would be true in either case

since its a parent to both

e.g. https://carc.in/#/r/bc4n

Ali Naqvi

@naqvis

true, case will end on the very first match, so for such scenario its better to move the parent or more general type to the end

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