Hi, In 40516 there is now a strange, but rather powerful mechanism for CompiledMethod: the Twin. What does that do? you can call on a method #createTwin (ReflectivityExamples>>#exampleMethod) createTwin. after this, the CompiledMethod has a high-level representation (the AST) attached that itself references the CompiledMethod (they form a twin). (ReflectivityExamples>>#exampleMethod) reflectiveMethod The fun thing is now that one can install either in the class. Call #invalidate to make sure the reflective method is installed. ReflectiveMethod implements #run:with:in: which calls a compilation hook (too re-create from the AST) and then installs that in the method dict and then executes the method: (ReflectivityExamples>>#exampleMethod) createTwin. (ReflectivityExamples>>#exampleMethod) invalidate. self assert: (ReflectivityExamples>>#exampleMethod) class = ReflectiveMethod. self assert: ReflectivityExamples new exampleMethod = 5. self assert: (ReflectivityExamples>>#exampleMethod) class = CompiledMethod. Which means that this gives us an in-image, on-demand JIT compiler AST->Bytecode. In 50 lines of code. e.g. try on Morph: Morph methods do: #createTwin. Morph methods do: #invalidate. Counting which twin is installed shows us the working set of Morph: (Morph methods select: [ :each | each class = CompiledMethod ]) size some 330 method out of nearly 900â¦. So what can one do with this? In essence this turns the AST into a reflective representation for Methods (if you care to set up twin creation + invalidation correctly). What will this allow us to do? stay tuned... Marcus