The let/app invariant, evaluated-ness, and reallyUnsafePtrEquality#

Git HEAD of containers compiles fine with ghc-8.0.1, but when compiling with GHC git HEAD gives core lint errors:

*** Core Lint errors : in result of Float out(FOS {Lam = Just 0,
                                                   Consts = True,
                                                   OverSatApps = False}) ***
<no location info>: warning:
    In the expression: tagToEnum#
                         @ Bool (reallyUnsafePtrEquality# @ (Set a) l'_a4Fk l_a4Fi)
    This argument does not satisfy the let/app invariant:
      reallyUnsafePtrEquality# @ (Set a) l'_a4Fk l_a4Fi
*** Offending Program ***
Rec {
$dTypeable_s9vn :: Proxy# Set -> TypeRep

This issue can be reproduced using:

(cd libraries/containers ; git checkout master ; git pull)
perl boot && ./configure && make clean && make -j

Trac metadata

Trac field	Value
Version	8.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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