Unable to infer type when using DuplicateRecordFields

It seems to me that GHC should be able to easily infer the types for the record updates in this simple example. Is there a reason that it is unable to infer the type currently?

{-# LANGUAGE OverloadedLabels, DuplicateRecordFields #-}
module C where

main = do
  print aThing
  print bThing
  print (aThing { a = 5 } )
  print (bThing { a = 5 } )

data B = B { a :: Int} deriving Show

bThing = B 10

data A = A { a :: Int } deriving Show

aThing = A 10

{-

[1 of 1] Compiling C                ( C.hs, C.o )

C.hs:7:10: error:
    • Record update is ambiguous, and requires a type signature
    • In the first argument of ‘print’, namely ‘(aThing {a = 5})’
      In a stmt of a 'do' block: print (aThing {a = 5})
      In the expression:
        do { print aThing;
             print bThing;
             print (aThing {a = 5});
             print (bThing {a = 5}) }
-}

Trac metadata

Trac field	Value
Version	7.10.3
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC	adamgundry
Operating system
Architecture