Issues with invoking lib functions in other ways

[papamarkou]

Crystal says i've hit a bug and I should report it by opening an issue, so although I don't know what is the origin of the bug, here is the error message:

Bug: LibDSFMT doesn't implement lookup_def_instance
*Exception#initialize<Exception, String, Nil>:Array(String) +21 [32]
*Exception::new<String>:Exception +125 [32]
*raise<String>:NoReturn +6 [32]
*Crystal::Type+@Crystal::Type#lookup_def_instance<Crystal::Type+, Crystal::DefInstanceKey>:NoReturn +89 [32]
*Crystal::Call#instantiate<Crystal::Call, Crystal::Matches, Crystal::Type+, Nil>:Array(Crystal::Def+) +4008 [32]
*Crystal::Call#lookup_matches_in_type<Crystal::Call, Crystal::Type+, Array(Crystal::Type+), Nil, String>:Array(Crystal::Def+) +25691 [32]
*Crystal::Call#lookup_matches_in<Crystal::Call, Crystal::Type+, Array(Crystal::Type+), Nil, String>:Array(Crystal::Def+) +11 [32]
*Crystal::Call#lookup_matches_in<Crystal::Call, Crystal::Type+, Array(Crystal::Type+)>:Array(Crystal::Def+) +161 [32]
*Crystal::Call#lookup_matches_without_splat<Crystal::Call, Array(Crystal::Type+)>:Array(Crystal::Def+)? +854 [32]
*Crystal::Call#lookup_matches<Crystal::Call>:Array(Crystal::Def+)? +431 [32]
*Crystal::Call#recalculate<Crystal::Call>:(Bool | Nil) +1834 [32]
*Crystal::TypeVisitor#visit<Crystal::TypeVisitor, Crystal::Call>:Bool +2718 [32]
*Crystal::ASTNode+@Crystal::ASTNode#accept<Crystal::ASTNode+, Crystal::TypeVisitor>:Nil +1792 [32]
*Crystal::TypeVisitor#visit<Crystal::TypeVisitor, Crystal::Path>:(Nil | Array(Crystal::Call) | Crystal::Type+ | Bool) +420 [32]
*Crystal::ASTNode+@Crystal::ASTNode#accept<Crystal::ASTNode+, Crystal::TypeVisitor>:Nil +3622 [32]
*Crystal::TypeVisitor#visit<Crystal::TypeVisitor, Crystal::Call>:Bool +630 [32]
*Crystal::ASTNode+@Crystal::ASTNode#accept<Crystal::ASTNode+, Crystal::TypeVisitor>:Nil +1792 [32]
*Crystal::Expressions#accept_children<Crystal::Expressions, Crystal::TypeVisitor>:Array(Crystal::ASTNode+) +108 [32]
*Crystal::ASTNode+@Crystal::ASTNode#accept<Crystal::ASTNode+, Crystal::TypeVisitor>:Nil +9151 [32]
*Crystal::Expressions#accept_children<Crystal::Expressions, Crystal::TypeVisitor>:Array(Crystal::ASTNode+) +108 [32]
*Crystal::Expressions@Crystal::ASTNode#accept<Crystal::Expressions, Crystal::TypeVisitor>:Nil +80 [32]
*Crystal::Program#infer_type<Crystal::Program, Crystal::Expressions>:Crystal::Expressions +32 [32]
*Crystal::Compiler#infer_type<Crystal::Compiler, Crystal::Program, Crystal::Expressions>:Crystal::Expressions +238 [32]
*Crystal::Compiler#compile<Crystal::Compiler, Array(Crystal::Compiler::Source), String>:Crystal::Compiler::Result +334 [32]
*Crystal::Command::CompilerConfig#compile<Crystal::Command::CompilerConfig, String>:Crystal::Compiler::Result +57 [32]
*Crystal::Command::run_command<Array(String)>:Nil +398 [32]
*Crystal::Command::run<Array(String)>:(Crystal::Compiler::Result | Bool | CFileIO | Nil) +161 [32]
*Crystal::Command::run:(Crystal::Compiler::Result | Bool | CFileIO | Nil) +34 [32]
__crystal_main +5597 [32]
main +40 [32]
__libc_start_main +245 [32]
_start +41 [32]
 +41 [32]

Error: you've found a bug in the Crystal compiler. Please open an issue: https://github.com/manastech/crystal/issues

[asterite]

Thanks for reporting!

Code to reproduce:

class A
  def self.foo
  end
end

lib B
  fun foo : Int32
end

(A || B).foo

What is your code doing? It's strange that you have a union of a lib type and a Crystal type.

[papamarkou]

Hm, I think I was doing sth meaningless. I wanted to define a constant, whose value is computed via a libdSFMT function binding. Instead of putting the constant definition in the DSFMT struct, i put it in libdSFMT, which wasns't so clever. Initially I had the statement MINSIZE = dsfmt_get_min_array_size in libdSFMT, but once I moved it to the DSFMT struct (as in MINSIZE = LibDSFMT.dsfmt_get_min_array_size), the problem was sorted (and this is more reasonable than my first approach if I am not wrong :) ). The relevant code is in the latest commit in random.cr

[asterite]

Hmm... do you have a small code to reproduce this issue? One way is the code I posted, but I'm not sure it's exactly the same issue. I checked out random.cr and ran the specs but they compile. How can I trigger the error?

[papamarkou]

Hey @asterite, so here is what I did to trigger the issue (some pseudocode below, in an attempt to disentangle the issue from dsfmt and generalize):

lib LibX
  MYCONSTANT = get_minimum_fee

  fun get_minimum_fee() : Int32
end

Basically, we have a binding to a C function and then we use it inside libX to call that function and assign its returned value to the constant MYCONSTANT. I guess I shouldn't be doing this in the first place?

Sorry for the late reply, it is due to the difference in time between Argentina and UK :)

[asterite]

Thanks! That's another way to reproduce the bug. I'll fix both of them... eventually.

You should be able to do what you did there, to have a constant based on the return value of a function. A constant in Crystal means: once the value is set, it can't change. But it doesn't mean that the value must be known at compile time. So you can for example do:

NOW = Time.now
puts NOW
puts NOW

That's a perfectly valid constant, only it's not constant across different runs, but only in each run.

No worries about the late reply, there's no need to hurry :-)

[papamarkou]

Yes, I am following what you say. Great, I will change the code in random.cr later, when the bug is fixed in Crystal!