libraries/base/GHC/Stack/Types.hs¶
Note [Definition of CallStack]¶
CallStack is defined very early in base because it is used by error and undefined. At this point in the dependency graph, we do not have enough functionality to (conveniently) write a nice pretty-printer for CallStack. The sensible place to define the pretty-printer would be GHC.Stack, which is the main access point, but unfortunately GHC.Stack imports GHC.Exception, which needs the pretty-printer. So the CallStack type and functions are split between three modules:
- GHC.Stack.Types: defines the type and simple functions
- GHC.Exception: defines the pretty-printer
- GHC.Stack: exports everything and acts as the main access point
