Hello, I spent some time to make Yi work with 6.8, and failed up to now. Before I go into details, let's see what I'm trying to do with Yi. The idea is to have a fully dynamic application where the user is allowed to run arbitrary haskell code on the command line. This can be used to quickly test new code, etc. In particular, one needs to be able to "reload" the configuration in that manner. This is achieved basically by having everything running inside a specially made "GHC Session". The dynamic code is able to "reload itself" because it is passed a pointer to the GHC session. The GHC experts will see here that this cannot work :) Indeed, GHC has a number of "global variables", which, if accessed through code loaded in a GHC session, will be instanciated again. This means that accessing a "level 1" session with "level 2" code is normally not possible. However, I found a workaround: encapsulate all calls to the GHC API in a data structure in "level 1" code, which is then passed to "level 2". (A haskell version of C-style callbacks). While this worked beautifully with GHC 6.6, it fails with 6.8rc. with exception :: GhcException yi: panic! (the 'impossible' happened) (GHC version 6.8.0.20071019 for i386-unknown-linux): a static opt was looked at too early! This happens at a seemingly unrelated point in the code. (inside the bytecode interpreter?) I can't really report a bug here, because what I'm trying to do is probably fairly unsupported by GHC. However, I'd appreciate some sort of advice. Is my workaround the correct approach? How would GHC people implement a dynamic application? Should I drop the idea completely? ... Thanks in advance for your help :) -- JP Attached: a darcs patch to the Yi repo to (try to) support 6.8.