We mustn't define operators or hash functions for types we don't own, esp. not in a header file, because when someone else gets the same idea, we have an ODR violation, unless they get it token-for-token the same as our implementation. One option would be to replace the QHash with an STL container. Those can take per-container Hash and Equal function objects, so we wouldn't need to declare the global ones. But let's use a wrapper around the type on which we define the missing operators instead. As a drive-by, rename the arguments to the idiomatic lhs/rhs/key, from a/b/s. Change-Id: Ibbc2083bcd7423c5d443a0ca1b820cbecb241865 Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>