ICE with untyped Array as instance var initializer

[xfbs]

I don't really know how to search if this bug has been posted before because I'm not sure what to search for, the error I'm getting is rather cryptic. This is the error I'm getting:

$ crystal build --verbose paths.cr 
cast from Nil to Crystal::GenericInstanceType+ failed, at /private/tmp/crystal-lang-20171012-68849-1f0n4y5/crystal-0.23.1/src/compiler/crystal/types.cr:1420:20:1420
0x10e81dc58: *raise<TypeCastError>:NoReturn at ??
0x10eee0cd4: *Crystal::TypeParameter#solve<Crystal::NonGenericClassType>:Crystal::ASTNode+ at ??
0x10eee1990: *Crystal::GenericInstanceType+@Crystal::GenericInstanceType#replace_type_parameters<Crystal::NonGenericClassType>:Crystal::Type+ at ??
0x10eedea0a: *Crystal::TypeDeclarationProcessor#process_owner_guessed_instance_var_declaration<Crystal::Type+, String, Crystal::TypeDeclarationProcessor::InstanceVarTypeInfo>:(Crystal::MetaTypeVar | Crystal::TypeDeclarationProcessor::Error | Nil) at ??
0x10eed86a3: *Crystal::TypeDeclarationProcessor#process_instance_vars_declarations:Nil at ??
0x10ee2adeb: *Crystal::Program#top_level_semantic<Crystal::ASTNode+>:Tuple(Crystal::ASTNode+, Crystal::TypeDeclarationProcessor) at ??
0x10ee24e09: *Crystal::Program#semantic<Crystal::ASTNode+, Bool>:Crystal::ASTNode+ at ??
0x10f2a35b5: *Crystal::Compiler#compile<Array(Crystal::Compiler::Source), String>:Crystal::Compiler::Result at ??
0x10e85bf8c: *Crystal::Command#run:(Bool | Crystal::Compiler::Result | IO::FileDescriptor | Nil) at ??
0x10e832ff6: main at ??

Error: you've found a bug in the Crystal compiler. Please open an issue, including source code that will allow us to reproduce the bug: https://github.com/crystal-lang/crystal/issues

This is the minimal file to trigger the bug:

class Paths
  def initialize(x, y)
    @count = Array.new(max_x){Array.new(max_y)}
  end
end

And this is the version of the compiler I'm using:

$ crystal -v
Crystal 0.23.1 (2017-10-12) LLVM 4.0.1

I'm running crystal on an OS X 10.11 El Capitan, and I installed crystal with homebrew if that makes any difference. Btw kudos to the team, I've really enjoyed playing with the language in the past few days!

[mig-hub]

@xfbs, Where do max_x and max_y come from? Is it a typo and you meant to put these names for the arguments of the method? or does the bug come from the fact that these variables don't exist?

[xfbs]

Oh, my bad. I guess I simplified the code too much before posting. So the original code that triggers the bug was something like this:

class Paths
  def initialize(x, y)
    max_x = 0
    max_y = 0
    @count = Array.new(max_x){Array.new(max_y)}
  end
end

So, both max_x and max_y exist. I think what triggers the bug is because I didn't specify the type of the Array — this code works:

Array(Array(Int32)).new(max_x){Array(Int32).new(max_y)}

I'm wildly guessing here that the compiler doesn't like the fact that I've omitted the type specifiers, and that triggered some kind of internal bug?

[bew]

Minimal:

Array.new(0) { Array.new(0) }

Fixed:

Array.new(0) { Array(Int32).new(0) }

[RX14]

Can anyone confirm if this is fixed by #4974? (and by extension 0.24.1) I'm 98% sure it's a dupe.

[larubujo]

same same but different. crashes in master

[RX14]

Works for me on master:

$ bin/crystal /tmp/test.cr
Using compiled compiler at `.build/crystal'
Error in /tmp/test.cr:1: instantiating 'Array(T):Class#new(Int32)'

Array.new(0) { Array.new(0) }
                     ^~~

in src/array.cr:77: can't infer the type parameter T for the generic class Array(T). Please provide it explicitly

  def initialize(initial_capacity : Int)

Did you make sure to make crystal before checking @larubujo?

[larubujo]

@RX14 try this, which is original/similar code by op:

class Paths
  def initialize
    @count = Array.new(0) { }
  end
end

[larubujo]

also for this, which is op code:

class Paths
  def initialize(x, y)
    max_x = 0
    max_y = 0
    @count = Array.new(max_x) { Array.new(max_y) }
  end
end

failure on both

[RX14]

Thanks. Seems using any type of generic parameter inference is broken but only at the class level.