bug Hash#fetch

[kostya]

class A
end

x = {} of Int32 => A
x.fetch(10) { A.new }

got big llvm error

Nil assertion failed:
*raise<String>:NoReturn + [53765888]
*Nil#not_nil!<Nil>:NoReturn + [53765888]
*Crystal::LLVMTyper#create_llvm_struct_type<Crystal::LLVMTyper, Crystal::NonGenericClassType+ | Crystal::Metaclass+ | Crystal::GenericClassInstanceType+ | Crystal::HierarchyType+>:Pointer(Void) + [53765888]
*Crystal::LLVMTyper#llvm_type<Crystal::LLVMTyper, Crystal::Type+>:Pointer(Void) + [53765888]
*Crystal::LLVMTyper#llvm_type<Crystal::LLVMTyper, Crystal::Type+>:Pointer(Void) + [53765888]
...

[asterite]

@kostya Thanks for reporting this. It's a bug we've known for some time but we still don't know how to fix it.

The good thing is that once you insert something in your hash, the error is gone (and typically a program will insert something in the hash, otherwise... why use it?).

But we believe it's something fixable. And the good thing is now this bug is being tracked somewhere :-)

[asterite]

The smallest example to reproduce it is this:

class Foo
  def initialize(@x)
  end

  def x
    @x
  end
end

p = Pointer(Foo).malloc(1)
p.value.x

Because Foo is never initialized, we never get to know the type of @x. So we can't tell LLVM what's the complete type of Foo.

We'll think of something...