I have a code that fails to compile (boo from SVN): ====== import System; class MyAttribute(Attribute): def constructor(t): pass class K: pass [assembly:MyAttribute(typeof(K))] ====== BCE0015: Node 'K' has not been correctly processed. When I replace typeof(K) with some string or integer literal - it works. When I replace typeof(K) with K, it works as well... ... BUT ... The code presented is actually generated from a code generator that is based on CodeDOM. Boo's CodeGenerator produces "typeof(T)" for CodeTypeOfExpression(typeof(T)). When I modify the CodeDOM provider to emit just "T" in this case: Index: BooCodeGenerator.boo =================================================================== — BooCodeGenerator.boo (revision 2308) +++ BooCodeGenerator.boo (working copy) @@ -92,6 +92,9 @@ protected override def GenerateBaseReferenceExpression(e as CodeBaseReferenceExpression) : Output.Write("super") + protected override def GenerateTypeOfExpression(e as CodeTypeOfExpression) : + OutputType(e.Type) + protected override def GenerateCastExpression(e as CodeCastExpression) : Output.Write("cast(") OutputType(e.TargetType) It works here but starts to fail in other places. The expression "typeof(K).Assembly" (written in C# syntax) becomes indistinguishable from K.Assembly which obviously fails, because K doesn't have a property named Assembly. I'm not sure if this is a CodeDOM bug or compiler bug so I'm filing in both categories.