#9562: Type families + hs-boot files = unsafeCoerce -------------------------------------+------------------------------------- Reporter: goldfire | Owner: ezyang Type: bug | Status: new Priority: high | Milestone: Component: Compiler | Version: 7.8.3 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: GHC accepts | Unknown/Multiple invalid program | Test Case: Blocked By: | Blocking: Related Tickets: #10270 | Differential Revisions: -------------------------------------+------------------------------------- Comment (by ezyang): Here is something curious: {{{ ezyang@sabre:~/Dev/haskell/T9562/p$ ghc --make D -fforce-recomp [1 of 5] Compiling A ( A.hs, A.o ) [2 of 5] Compiling B[boot] ( B.hs-boot, B.o-boot ) [3 of 5] Compiling C ( C.hs, C.o ) [4 of 5] Compiling B ( B.hs, B.o ) [5 of 5] Compiling D ( D.hs, D.o ) B.hs:8:15: Conflicting family instance declarations: type instance F a b -- Defined at B.hs:8:15 type instance F a b -- Defined at D.hs:8:15 }}} however, {{{ ezyang@sabre:~/Dev/haskell/T9562/p$ ghc --make B C D A -fforce-recomp [1 of 5] Compiling A ( A.hs, A.o ) [2 of 5] Compiling B[boot] ( B.hs-boot, B.o-boot ) [3 of 5] Compiling C ( C.hs, C.o ) [4 of 5] Compiling D ( D.hs, D.o ) [5 of 5] Compiling B ( B.hs, B.o ) }}} I don't know why in the latter case no error is reported. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9562#comment:10 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler