Panic using mixing list with parallel arrays incorrectly

ghc: panic! (the 'impossible' happened)
  (GHC version 7.4.1 for i386-unknown-linux):
	DsMonad: uninitialised ds_parr_bi

Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug

changed weight to 5

added Tbug Trac import labels

Attached file Handy.hs ($740).

Attached file Main.hs ($741).

assigned to @mchakravarty

changed title from Requested to report bug as below. to Panic using mixing list with parallel arrays incorrectly

GHC shouldn't panic, but instead give a proper error message, but the definition of transpose in Handy.hs is incorrect. It uses list pattern matching with (:) for parallel arrays. That is impossible as they are not inductively defined.

Trac metadata

Trac field	Value
TypeOfFailure	ValidProgramRejected → CompileTimeCrash

added compiler crash label

Replying to [ticket:7078#comment:63042 chak]:

GHC shouldn't panic, but instead give a proper error message, but the definition of transpose in Handy.hs is incorrect. It uses list pattern matching with (:) for parallel arrays. That is impossible as they are not inductively defined.

Thanks for that. Naive coding. I have changed transposeP to this, and still get the same error.

ansposeP !a = [: [:x !: i | x <- a:] | i <- [:0..l:]:]

where l = (lengthP (a !: 0)) P.- 1

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changed milestone to %7.8.1

mentioned in issue #7736 (closed)

changed milestone to %7.10.1

Moving to 7.10.1.

Trac metadata

Trac field	Value
Related	→ #7736 (closed)

removed milestone

Moving to 7.12.1 milestone; if you feel this is an error and should be addressed sooner, please move it back to the 7.10.1 milestone.

changed milestone to %8.0.1

Milestone renamed

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