id,summary,reporter,owner,description,type,status,priority,milestone,component,version,resolution,keywords,cc,os,architecture,failure,difficulty,testcase,blockedby,blocking,related
2888,Source file that compiled fine no longer compiles after touching it.,Eelis-,igloo,"In the following session, {{{t.hs}}} first compiles fine, then after being touched, no longer does:
{{{
  eelis ~/sand : cat M.hs
  {-# LANGUAGE TypeFamilies #-}
  module M where
  class C a where data D :: * -> *

  eelis ~/sand : cat t.hs
  {-# LANGUAGE TypeFamilies #-}
  import M
  data Bla = Bla
  instance C Bla where data D a = D
  main = return ()

  eelis ~/sand : ghc --make t.hs
  [1 of 2] Compiling M                ( M.hs, M.o )
  [2 of 2] Compiling Main             ( t.hs, t.o )
  Linking t ...

  eelis ~/sand : touch t.hs

  eelis ~/sand : ghc --make t.hs
  [2 of 2] Compiling Main             ( t.hs, t.o )

  t.hs:4:21:
      Type indexes must match class instance head
      Found a but expected Bla
      In the associated type instance for `D'
      In the instance declaration for `C Bla'
}}}
It seems to me that {{{t.hs}}} should either compile both times, or not compile at all, but not only part of the time.
",merge,closed,normal,,Compiler,6.10.1,fixed,,,Unknown/Multiple,Unknown/Multiple,,Unknown,indexed-types/should_fail/T2888,,,