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  • Glasgow Haskell CompilerGlasgow Haskell Compiler
  • GHCGHC
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  • #8553
Closed
Open
Issue created Nov 21, 2013 by Joachim Breitner@nomeataDeveloper

ASSERT failed compiler/typecheck/TcMType.lhs line 809

With current master (9c2dade9) I get

[1 of 1] Compiling ShouldCompile    ( ../ghc/gadt6.hs, ../ghc/gadt6.o )
ghc-stage2: panic! (the 'impossible' happened)
  (GHC version 7.7.20131121 for x86_64-unknown-linux):
	ASSERT failed!
    file compiler/typecheck/TcMType.lhs line 809
    [W] cobox_aBx{v} [lid] :: t_aBv{tv} [tau[0]]
                              ghc-prim:GHC.Types.~{(w) tc 31Q} t_aBu{tv} [tau[0]] (CIrredEvCan)

(And it took me a while to figure out that it was not my code that was introducing the bug.)

According to git log -L 809,809:compiler/typecheck/TcMType.lhs (a useful feature) the history of the ASSERT is:

  • SPJ, “Accommodate Derived constraints in two places”, Sep 17, 8cfbdccb
  • SPJ, “Fix an ASSERT”, Oct 1 2012, adb6bcb7
  • SPJ, “Tidy up and simplify TcMType.zonkFlats”, Sep 17, 2012, bd6b183e
Trac metadata
Trac field Value
Version 7.6.3
Type Bug
TypeOfFailure OtherFailure
Priority normal
Resolution Unresolved
Component Compiler (Type checker)
Test case
Differential revisions
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