Hello, I'm interested in inspecting the strictness of functions at runtime and the depth of thunks "in the wild." For this reason I'm modifying GHC 8.10.2, essentially to add additional information to breakpoints. I'd like to reuse the logic behind GHCi's :print command (pprintClosureCommand, obtainTermFromId, ...) for which I suppose I need Id's. Those however don't exist for destructuring patterns, such as those in the following equations: last [x] = x last (_:xs) = last xs So I'm wondering where would be a good place in the pipeline to transform patterns like these into at-patterns, to give them Id's. However, the breakpoint logic only looks at the free variables of the right-hand sides and not transitively, which means that e.g. in the following example neither ':print arg1' nor ':print as' works when the interpreter hits a breakpoint in the top level expression on the RHS: qsort arg1@(a:as) = qsort left ++ [a] ++ qsort right where (left, right) = (filter (<=a) as, filter (>a) as) Thus I'd also like to know how to extend the free var logic for Tickish that eventually leads to CgBreakInfo and :print's ability to inspect these bindings at runtime. My goal would be to determine to what extent was a thunk evaluated during function application. Any advice would be greatly appreciated! Regards, Andrew Kvapil