id,summary,reporter,owner,description,type,status,priority,milestone,component,version,resolution,keywords,cc,os,architecture,failure,difficulty,testcase,blockedby,blocking,related
481,Recompilation check fails for TH,simonpj,simonmar,"The recompilation check only recompiles a module when 
the ''interface'' of a module it imports changes.  But 
with Template Haskell, it may need to be recompiled 
when the ''implementation'' changes.

Concrete example below.  It's quite awkward to fix.

 * Perhaps a module that contains any splices should be recompiled always.
 * Perhaps a module that exports any TH stuff (how would we tell?) should be flagged as changed if anything about it changes.  

Simon

The following scenario reproduces this error
(thanks to Bulat Ziganshin bulatz@HotPOP.com):

1) create Main.hs containing code

{{{
module Main where
import Sub
main = print $x
}}}

and Sub.hs containing code

{{{
module Sub where
x = [| 1 |]
}}}

2) compile them with --make:

{{{
C:\!\Haskell\!>ghc --make -fth Main.hs
Chasing modules from: Main.hs
Compiling Sub              ( ./Sub.hs, ./Sub.o )
Compiling Main             ( Main.hs, Main.o )
Loading package base-1.0 ... linking ... done.
Loading package haskell98-1.0 ... linking ... done.
Loading package template-haskell-1.0 ... linking ... 
done.
Linking ...

C:\!\Haskell\!>main.exe
1
}}}

3) now change Sub.hs to the following code:

{{{
module Sub where
x = [| 2 |]
}}}

4) and recompile program:

{{{
C:\!\Haskell\!>ghc --make -fth Main.hs
Chasing modules from: Main.hs
Compiling Sub              ( ./Sub.hs, ./Sub.o )
Skipping  Main             ( Main.hs, Main.o )
Linking ...

C:\!\Haskell\!>main.exe
1
}}}

As you see, Main.hs is not recompiled despite the fact 
that definition
of x is changed and now program must print ""2""",bug,closed,normal,7.2.1,Template Haskell,6.4.1,fixed,,jonas.duregard@…,Unknown/Multiple,Unknown/Multiple,Incorrect result at runtime,Unknown,TH_recompile,,,