@hackage file-location0.4.9.1

Common debugging/error/exception functions that give file location information

$(err "OH NO!")
main:Main main.hs:16:1 OH NO!

Notice how it displays package:module file:line:character

It exposes the functions err (error), undef (undefined), and trc (Debug.Trace.trace). All of these behave the same as their normal counterpart but also spit out a location.

Here is my favorite helper, debug, which is like trace but just show the value.

debug [1,2,3]
DEBUG: [1,2,3]
[1,2,3]

And The Template Haskell version.

$(dbg) [1,2,3]
DEBUG main:Main main.hs:1:3 [1,2,3]
[1,2,3]

Also there is a version of thrwIO that gives location information

($(thrwIO) $ AException) catch e -> putStrLn ("Caught " ++ show (e :: AException))
Caught AException "main:Main test/main.hs:25:6"

See module for a listing of all the functions with short descriptions, and the homepage for some more examples https://github.com/gregwebs/ErrorLocation.hs