[GHC] #10333: hs-boot modification doesn't induce recompilation

[GHC]

#10333: hs-boot modification doesn't induce recompilation
-------------------------------------+-------------------------------------
              Reporter:  ezyang      |             Owner:
                  Type:  bug         |            Status:  new
              Priority:  normal      |         Milestone:
             Component:  Compiler    |           Version:  7.11
              Keywords:              |  Operating System:  Unknown/Multiple
          Architecture:              |   Type of failure:  GHC accepts
  Unknown/Multiple                   |  invalid program
             Test Case:              |        Blocked By:
              Blocking:              |   Related Tickets:
Differential Revisions:              |
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 Consider these modules:

 X.hs-boot
 {{{
 module X where
 }}}

 Y.hs
 {{{
 module Y where
 import {-# SOURCE #-} X
 data T = T
 data S = S T
 }}}

 X.hs
 {{{
 module X where
 import Y
 }}}

 `ghc --make Y.hs` will compile fine. Now, modify `X.hs-boot` to add a
 `data T` (which will cause an ambiguous identifier error in Y.hx`. Run
 `ghc --make Y.hs` and nothing happens!

 (You might also notice something else a bit funny, which is that `X.hs`
 gets compiled, even though it's not directly in the import chain of Y. I
 think this might be intentional but I'm not sure.)

 Discovered this while poking around #10182.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10333>
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