Proposal: Warn when using Enum instance of Float or Double

[harry]

The Enum instances for Float and Double have dubious semantics which cause
endless confusion, e.g.
http://stackoverflow.com/questions/13203471/the-math-behind-1-0999999999999999-in-haskell,
http://stackoverflow.com/questions/9810002/floating-point-list-generator,
http://stackoverflow.com/questions/7290438/haskell-ranges-and-floats,
http://stackoverflow.com/questions/10328435/how-to-solve-floating-point-number-getting-wrong-in-list-haskell,
and many more.

I would therefore like to propose that the usage of an Enum instance of
Float or Double generate a compiler warning, such as "The Enum instance of
Float is subject to rounding errors". Deadline: 2 weeks.

Pedantic question: Should it be the Enum instance _of_ Float or _for_ Float?




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