ghci doesn't always use compiled modules

Here is a small program:

module T where
foo :: Int -> Int
foo n = n+1

module U where
import T
main = print (foo 1)

Now I do this:

$ ghc -c T.hs
$ runhaskell -v U.hs
...
[1 of 2] Skipping  T                ( T.hs, T.o )
...  
$ touch T.hs
$ runhaskell -v U.hs
...
[1 of 2] Compiling T                ( T.hs, interpreted )
...
$ ghc -c T.hs -fforce-recomp
$ runhaskell -v U.hs
...
[1 of 2] Compiling T                ( T.hs, interpreted )
...

Note that runhaskell doesn't use T.o even though I recompiled T. As far as I understand, this is because compilation has regenerated T.o but hasn't updated T.hi because the interface hasn't changed. So T.hi is older than T.hs and ghci seems to ignore the compiled version in this case. I'm not sure why the .hi file's timestamped is checked here, it seems that checking the .o file should be sufficient.

Trac metadata

Trac field	Value
Version	7.2.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system
Architecture