Hello everyone, Reflectivity beta is out ! Reflectivity is a tool that permit to annotate AST nodes with "metalinks". You can put metalinks at different "positions": before: the metalink is executed before the node instead: the metalink is executed instead the node after: the metalink is executed after the node onError: the metalink is executed only if the execution of the node raises an error onSuccess: the metalink is executed only if the execution of the node raises no error When you put metalinks on some node of a method's AST, a wrapper is installed in place of the method. When executed, this wrapper compiles an expanded version of the AST that takes metalinks into account and install the resulting compiled method. Examples: increaseAllNumbersIn: aCompiledMethod "A method that increases all numbers in aCompiledMethod" aCompiledMethod reflectiveAST forAllNodes: [ :node | node isLiteral and: [ node value isNumber ] ] putInstead: [ :node | RFMetalink fromExpression: (node value + 1) asString ]. removeMetalinksIn: aCompiledMethod aCompiledMethod reflectiveAST removeAllMetalinks In nautilus, you have a menu entry called 'Edit metalinks' that permit to edit the metalinks of the node corresponding to the selected piece of code. As an example use case, another entry called 'Put breakpoint' adds a metalink that corresponds to 'Halt now' before the selected node. Remember that it is a beta, so you might find errors and things are likely to change. You can load Reflectivity with: Gofer it smalltalkhubUser: 'RMoD' project: 'Reflectivity'; configuration; loadDevelopment Or you can download it from RMoD's CI: https://ci.inria.fr/rmod/job/Reflectivity/ Camille