Absail's hash.h states that the hash might depend on the C++ type and gives as an example that int and double might not hash the same. patrick.freed@mongodb.com has found that in the latest abseil equal values of int32 and int64 types might produce different hashes.

Note: in value::hashValue we already hash as int64_t doubles and decimals that can be represented as int64_t (and presumably those that cannot be represented as such won't compare equal to any int64_t values).