runghc does not infer module file extensions

In ghc-6.8 (and possibly earlier), runghc will infer the extension of a module filename if it is not specified at the command line. This feature lets us type, for example, runghc Setup configure without worrying whether there's a Setup.lhs or Setup.hs file present.

For example:

$ cat Useful.hs 
main = putStrLn "Hello, world"
$ runghc Useful
Hello, world

However, this does not work for ghc-6.9.20080824:

$ ~/tmp/ghc-stage/bin/runghc Useful

<no location info>: can't find file: Useful
$ ~/tmp/ghc-stage/bin/runghc Useful.hs
Hello, world

Trac metadata

Trac field	Value
Version	6.8.3
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system	Unknown
Architecture	Unknown