tmp$ booc -r:attr.dll attruser.boo
Boo Compiler version 0.9.3.3478 (2.7 (/trunk/mono r154183 Thu Mar 25 16:08:41 SGT 2010))
at System.Reflection.MonoCMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) [0x00000] in <filename unknown>:0
at System.Reflection.MonoCMethod.Invoke (BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) [0x00000] in <filename unknown>:0
at System.Activator.CreateInstance (System.Type type, BindingFlags bindingAttr, System.Reflection.Binder binder, System.Object[] args, System.Globalization.CultureInfo culture, System.Object[] activationAttributes) [0x00000] in <filename unknown>:0
at System.Activator.CreateInstance (System.Type type, System.Object[] args, System.Object[] activationAttributes) [0x00000] in <filename unknown>:0
at System.Activator.CreateInstance (System.Type type, System.Object[] args) [0x00000] in <filename unknown>:0
at Boo.Lang.Compiler.Steps.MacroProcessing.ApplyAttributeTask.CreateAstAttributeInstance () [0x00000] in <filename unknown>:0
at Boo.Lang.Compiler.Steps.MacroProcessing.ApplyAttributeTask.Execute () [0x00000] in <filename unknown>:0
attruser.boo(1,2): BCE0009: An error occurred during the resolution of the 'Method' ast attribute: 'parameters do not match signature'.
1 error(s).
Forgot to change priority: it actually should be Critical/Blocker.
The code is valid and compiles successfully under Windows.