Bad hpc hash function

In the hpc module Trace.Hpc.Util there is the following code:

instance (HpcHash a,HpcHash b) => HpcHash (a,b) where
  toHash (a,b) = toHash a * 33 `hxor` toHash b

This is bad and I can only presume that what was actually intended was

instance (HpcHash a,HpcHash b) => HpcHash (a,b) where
  toHash (a,b) = (toHash a * 33) `hxor` toHash b

Otherwise a hash of 0 for a will result in a total hash of 0.

Trac metadata

Trac field	Value
Version	7.2.2
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Code Coverage
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