Data.Word64: arithmetic overflow when evaluating maxBound + 1

[guest]

The function (fromInteger x) in Num(Data.Word.Word64) causes a program error, if x is greater or equal 2⁶⁴. This is particularly annoying when two valid Word64 variables are to be multiplied.

Take for instance

Data.Word> maxbound :: Word64
18446744073709551615
Data.Word> 2*(2^63) :: Word64

Program error: arithmetic overflow

Data.Word> (2^64) :: Word64

Program error: arithmetic overflow

GHC and GHCi return values mod 2⁶⁴, as Hugs does also for Word32 and 2³².