[GHC] #2648: Report out of date interface files robustly

[GHC]

#2648: Report out of date interface files robustly
---------------------------------+------------------------------------------
    Reporter:  simonpj           |       Owner:                  
        Type:  feature request   |      Status:  new             
    Priority:  normal            |   Milestone:  6.12 branch     
   Component:  Compiler          |     Version:  6.8.3           
    Severity:  normal            |    Keywords:                  
  Difficulty:  Unknown           |    Testcase:                  
Architecture:  Unknown/Multiple  |          Os:  Unknown/Multiple
---------------------------------+------------------------------------------
 Suppose `X.hi` refers to `Y.f77`, but `Y.hi` is out of date and has no
 `f77`. Then you get a bad crash:
 {{{
 (GHC version 6.8.3 for i386-unknown-mingw32):
     tcIfaceGlobal (local): not found:
 Please report this as a GHC bug
 }}}
 The solution lies within our grasp:
  * X.hi already contains a fingerprint for Y.hi
  * So, we should simply check Y.hi's fingerprint when we suck it in
 (Currently we do this fingerprint checking only for the module we are
 currently compiling, to see if the bits it depends on have changed.)

 Simon

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/2648>
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