Crystal: Another generics error

[Grabli66]

Code:

abstract class Protocol
end

# Base modbus protocol
abstract class ModbusProtocol < Protocol
end

# Base modbus protocol
class ModbusRtuProtocol < ModbusProtocol
end

# Base device info
abstract class DeviceInfo
end


# Base device info
class MeterDeviceInfo < DeviceInfo
  # Device network number
  getter networkNumber : Int32 = 1
end

# Base driver task executer
abstract class CollectorDriverExecuter(TDevice, TProtocol, TResponseType)
  def initialize(@deviceInfo : TDevice, @protocol : TProtocol)      
  end

  def initialize(@deviceInfo : TDevice, @protocol : TProtocol, &block : TResponseType -> _)
    execute(&block)
  end

  # Execute and iterate values in block
  abstract def execute(&block : TResponseType -> _)
end

# Base executer
abstract class BaseExecuter(TResponseType) < CollectorDriverExecuter(MeterDeviceInfo, ModbusRtuProtocol, TResponseType)
end

# Common executer with start session
abstract class CommonExecuter(TResponseType) < BaseExecuter(TResponseType)
  # To implement
  abstract def postExecute(&block : TResponseType -> _) : Void    

  # Start session and execute other
  def execute(&block : TResponseType -> _) : Void
    StartSessionExecuter.new(@deviceInfo, @protocol) do
      postExecute(&block)
    end        
  end
end

class StartSessionExecuter < BaseExecuter(Bool)   
  def execute(&block : Bool -> _)
    data = Bytes[0xCC, 0x80, 0x00, 0x00, 0x00]
    p data
  end
end

StartSessionExecuter.new(MeterDeviceInfo.new, ModbusRtuProtocol.new) do
end

Error:
Error in line 60: instantiating 'StartSessionExecuter:Class#new(MeterDeviceInfo, ModbusRtuProtocol)'

in line 29: instantiating 'execute()'

in line 55: expanding macro

in /usr/lib/crystal/slice.cr:34: undefined constant T

{% if @type.name != "Slice(T)" && T < Number %}
                                  ^

Crystal 0.25.1 (2018-06-29)
LLVM: 6.0.0
Default target: x86_64-pc-linux-gnu

https://play.crystal-lang.org/#/r/4l20

[straight-shoota]

Reduced:

def execute
  Bytes[1_u8]
end

execute

https://play.crystal-lang.org/#/r/4l2k

Error in line 5: instantiating 'execute()'

in line 2: expanding macro

in /usr/lib/crystal/slice.cr:34: undefined constant T

    {% if @type.name != "Slice(T)" && T < Number %}

The error does not happen when Bytes.[] is called from to level scope or Slice.[] is used.

[bew]

Duplicate of #5343

[bew]

This can be closed now that #5354 is merged

[Grabli66]

I tested it, and it works.
Thanks.