Sounds useful to me (though one might occasionally want to have access to just the current location, without context - suggesting perhaps a list/stack of strings rather than a pre-concatenated string).
actually, there's a bit about your proposal (on the wiki page) that I don't quite follow, namely whether the annotated function versions are hand-written (needed only for making explicit use of the annotation parameter) or generated (convenient for passing on the annotation parameter). here are the use cases I can see arising: case 1: I want to have explicit access to the call site location info - I write both head and headError, and the pragma - calls to head will be translated into calls to headError <srcLoc>, where I can process that information however I need to. {-# SRC_LOC_ANNOTATE head #-} head (h:_) = h headError srcLoc (h:_) = h headError srcLoc _ = error ("head of empty list: "++show srcLoc) case 2: I have a function that calls annotated functions 2a: I want to have explicit access to the location info - I write both the function and its variant, and the pragma - calls to the function will be translated into annotated calls to its variant, I have to handle the information myself 2b: I just want to build up call stack information - I write only the function, and its pragma - a variant is generated, affecting calls to annotated functions as described on the web page case 0: I have a function with non-exhaustive left-hand sides, and I want the default branch to refer to the call site - I write only head, and its pragma - a definition of headError is generated, differing from head only in the extra parameter, and in the error branch which refers to that parameter (see case 1 for code) - calls to head will be translated into calls to headError <srcLoc>. {-# SRC_LOC_ANNOTATE head #-} head (h:_) = h [instead of generating variants as separate functions, one might simply transform the originals; the default branch should also be augmented in 2b, as in 0] cases 1&2 are as on the wiki page, where I think 2b is suggested, as a convenient default. case 2a would arise naturally if we annotate a function that also happens to call other annotated functions. and case 0 is the one that started this discussion, so it would be nice not to have to write out the boilerplate variants by hand. does this make sense? claus