crystal error message

can't instantiate StaticArray(T, N) with N = Int32 (N must be an integer)
*raise<String>:NoReturn +70 [0]
*Crystal::StaticArrayType#new_generic_instance<Crystal::StaticArrayType, Crystal::Program, Crystal::GenericClassType+, Hash(String, Crystal::ASTNode+)>:Crystal::StaticArrayInstanceType +434 [0]
*Crystal::GenericClassType+@Crystal::GenericType#instantiate<Crystal::GenericClassType+, Array((Crystal::Type+ | Crystal::ASTNode+))>:Crystal::GenericClassInstanceType+ +1105 [0]
*Crystal::ASTNode+@Crystal::ASTNode#accept<Crystal::ASTNode+, Crystal::Call::MatchTypeLookup>:Nil +4305 [0]
*Crystal::Call#match_block_arg<Crystal::Call, Crystal::Match>:({Array(Crystal::Var+)?, (Crystal::Type+ | Nil)} | {Nil, Nil}) +678 [0]
*Crystal::Call#instantiate<Crystal::Call, Crystal::Matches, Crystal::Program, Nil>:Array(Crystal::Def+) +902 [0]
*Crystal::Call#lookup_matches_in_type<Crystal::Call, Crystal::Program, Array(Crystal::Type+), Nil, String>:Array(Crystal::Def+) +1620 [0]
*Crystal::Call#recalculate<Crystal::Call>:Array(Crystal::Def+)? +2155 [0]
*Crystal::TypeVisitor#visit<Crystal::TypeVisitor, Crystal::Call>:Bool +10239 [0]
*Crystal::ASTNode+@Crystal::ASTNode#accept<Crystal::ASTNode+, Crystal::TypeVisitor>:Nil +2099 [0]
*Crystal::ASTNode+@Crystal::ASTNode#accept<Crystal::ASTNode+, Crystal::TypeVisitor>:Nil +23044 [0]
*Crystal::Compiler#compile<Crystal::Compiler, Array(Crystal::Compiler::Source), String>:Crystal::Compiler::Result +4403 [0]
*Crystal::Command::run_command<Array(String)>:Nil +319 [0]
*Crystal::Command::run<Array(String)>:(Array(Crystal::Init::View+:Class) | Crystal::Compiler::Result | File | Bool | CFileIO | Nil) +67 [0]
main +15450 [0]
__libc_start_main +245 [0]
_start +41 [0]
 +41 [0]

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