Backtrace of Crystal compiler error when trying @grid = Array.new(@size_x) { |i| [0] }

gistfile1.txt

Svens-MacBook-Pro-2:src sven$ crystal world.cr 
cast from Nil to Crystal::GenericInstanceType+ failed, at /private/tmp/crystal-lang-20180127-57131-6tccbo/crystal-0.24.1/src/compiler/crystal/types.cr:1428:20:1428
Crystal::TypeParameter#solve<Crystal::NonGenericClassType>:Crystal::ASTNode+
Crystal::GenericInstanceType+@Crystal::GenericInstanceType#replace_type_parameters<Crystal::NonGenericClassType>:Crystal::Type+
Crystal::TypeDeclarationProcessor#process_owner_guessed_instance_var_declaration<Crystal::Type+, String, Crystal::TypeDeclarationProcessor::InstanceVarTypeInfo>:(Crystal::MetaTypeVar | Crystal::TypeDeclarationProcessor::Error | Nil)
Crystal::TypeDeclarationProcessor#process_instance_vars_declarations:Nil
Crystal::Program#top_level_semantic<Crystal::ASTNode+>:Tuple(Crystal::ASTNode+, Crystal::TypeDeclarationProcessor)
Crystal::Program#semantic<Crystal::ASTNode+, Bool>:Crystal::ASTNode+
Crystal::Compiler#compile<Array(Crystal::Compiler::Source), String>:Crystal::Compiler::Result
Crystal::Command#run_command<Bool>:Nil
Crystal::Command#run:(Bool | Crystal::Compiler::Result | IO::FileDescriptor | Nil)
main

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
Svens-MacBook-Pro-2:src sven$