[Interpeter] BUG: called llvm_struct_type for (Log::ShortColorFormat | TestFormat) (Exception)

[Vici37]

I'm playing around with I3oris/ic on my largest project to see what edge cases I can run into. ic is a bit ahead of crystal's interpreter as it has the change from #12061 merged already, and this bug only appears after that one is fixed. Thankfully, this bug comes from one of my shards I've split out, so I have a simple reproducer below.

Stack trace:

BUG: called llvm_struct_type for (Log::ShortColorFormat | TestFormat) (Exception)                          
  from lib/ic/share/crystal-ic/src/compiler/crystal/codegen/llvm_typer.cr:365:7 in 'create_llvm_struct_type'    
  from lib/ic/share/crystal-ic/src/compiler/crystal/codegen/llvm_typer.cr:263:33 in 'llvm_struct_type'
  from lib/ic/share/crystal-ic/src/compiler/crystal/codegen/llvm_typer.cr:257:5 in 'llvm_struct_type'          
  from lib/ic/share/crystal-ic/src/compiler/crystal/codegen/codegen.cr:99:26 in 'instance_size_of'   
  from lib/ic/share/crystal-ic/src/compiler/crystal/interpreter/context.cr:324:11 in 'aligned_instance_sizeof_type'
  from lib/ic/share/crystal-ic/src/compiler/crystal/interpreter/compiler.cr:3210:5 in 'aligned_instance_sizeof_type'
  from lib/ic/share/crystal-ic/src/compiler/crystal/interpreter/primitives.cr:134:20 in 'visit_primitive'
  from lib/ic/share/crystal-ic/src/compiler/crystal/interpreter/primitives.cr:9:11 in 'visit_primitive'  
[snipped]

Reproducing:

> git clone https://github.com/Vici37/cr-color-logging
> cd cr-color-logging
> shards install
> ./bin/ic spec/color-logging_spec.cr

The shard is largely a reproduction of ShortFormat but with color configuration support added (I thought it looked a little bland).

[Vici37]

@I3oris new issue I ran into with ic

[I3oris]

Reduced!:

require "log"

abstract struct Parent
  extend Log::Formatter

  def self.format(entry, io) : Nil
    new
  end
end

struct Child1 < Parent
end

struct Child2 < Parent
end

But it could surely be reduced more by going through log.

self.format is an abstract method defined by Log::Formater.

The bug doesn't happen if struct is replaced by class, It doesn't happen if format is defined in both Child classes instead of Parent.

Hope this help :)

[I3oris]

After unfolding the log API I could reduce more:

module Formatter
end

abstract struct Parent
  extend Formatter

  def self.format
    new
  end
end

struct Child1 < Parent
end

struct Child2 < Parent
end

class Backend
  def initialize(@formatter : Formatter = Child1)
  end

  def write
    @formatter.format
  end
end

Backend.new.write

It seems when calling @formatter.format it tries to instantiate new on Parent because it includes Formatter, but Parent is abstract. However it work well with normal crystal run.

[I3oris]

In fact, it's weird that is def initialize(@formatter : Formatter = Child1).

def initialize(@formatter : Formatter.class = Child1) sound more logical to me. but it doesn't compile:

Error: can't restrict Child1.class to Formatter.class

However that was the equivalent of what is in the log API. Maybe a bug here ?, or it's a property of extend keyword?

crystal/src/log/io_backend.cr

Lines 12 to 14 in b7377c0

	def initialize(@io = STDOUT, *, @formatter : Formatter = ShortFormat, dispatcher : Dispatcher::Spec = DispatchMode::Async)
	super(dispatcher)
	end

[asterite]

I looked into it a bit. It's because we are missing handling virtual struct types in the interpreter. I'll probably fix it later this week.