GHC -O0 goes into a loop

[EyalLotem]

-O1/-O2 don't loop.

If I remove some of the types or the UNPACK, the problem ceases to reproduce.

It does not reproduce on 7.4.1 or 7.0.4.

Reproduces on multiple machines with 7.6.1.

[EyalLotem]

Reproduces the bug

[EyalLotem]

This also sends ghc7.6.1 -O0 into a loop:

data V = V {-# UNPACK #-} !V

But is of course illegal. The attached example:

data V = V {-# UNPACK #-} !L data L = L V

should be legal and also sends ghc into a loop.

[int-e]

Note that the second example,

data V = V {-# UNPACK #-} !L
data L = L V 

produces an "unusable UNPACK pragma" warning (but not always, see #7447) if compiled with -O1 or -O2. This also seems wrong -- I would expect the compiler to unpack it into something isomorphic to data V = V V.

P.S. reproduced on x86_64.

[maxtaldykin]

possible duplicate #7310

[EyalLotem]

It is a duplicate indeed.