Type error but types match

> unboxedsums git:(prim_sums_rebase_5) x cat primop_bug.hs
{-# LANGUAGE MagicHash, ScopedTypeVariables, UnboxedTuples #-}

module Main where

import GHC.MVar
import GHC.Prim
import GHC.Types

main :: IO ()
main = IO (\rw -> newMVar# rw) >> return ()

> unboxedsums git:(prim_sums_rebase_5) x ghc-stage1 primop_bug.hs -ddump-stg -ddump-cmm -ddump-to-file -fforce-recomp -dumpdir primop_fails -O -fprint-explicit-kinds
[1 of 1] Compiling Main             ( primop_bug.hs, primop_bug.o )

primop_bug.hs:10:19: error:
    • Couldn't match a lifted type with an unlifted type
      Expected type: (# State# RealWorld, MVar# RealWorld a0 #)
        Actual type: (# State# RealWorld, MVar# RealWorld a0 #)
    • In the expression: newMVar# rw
      In the first argument of ‘IO’, namely ‘(\ rw -> newMVar# rw)’
      In the first argument of ‘(>>)’, namely ‘IO (\ rw -> newMVar# rw)’

Tried with HEAD, 8.0.1.

Trac metadata

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