On 22 Sep 2017, at 13:43, Dominic wrote:

Coincidentally, I was playing with this a few days ago. I didn’t seem to have to do anything to get a warning.

...

GHCi, version 8.0.2: http://www.haskell.org/ghc/ :? for help Prelude Data.Word> :m Data.Int Prelude Data.Int> 0x80000000 :: Int32

<interactive>:27:1: warning: [-Woverflowed-literals] Literal 2147483648 is out of the Int32 range -2147483648..2147483647 If you are trying to write a large negative literal, use NegativeLiterals -2147483648 Prelude Data.Int> :set -XNegativeLiterals Prelude Data.Int> 0x80000000 :: Int32

<interactive>:29:1: warning: [-Woverflowed-literals] Literal 2147483648 is out of the Int32 range -2147483648..2147483647 -2147483648

I am not clear why it wanted me to use NegativeLiterals but still give the same warning. Does anyone understand the intent here?

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Message: 1 Date: Fri, 22 Sep 2017 14:14:12 +0200 From: Herbert Valerio Riedel To: Niklas Hambüchen Cc: Haskell Libraries Subject: Re: Deprecating fromIntegral Message-ID: Content-Type: text/plain; charset="UTF-8"

...there's one minor detail I'd like to point out as it doesn't seem to have been mentioned so far:

On Thu, Sep 21, 2017 at 5:34 PM, Niklas Hambüchen wrote:

...

(Though, in practice the current `fromInteger is not partial, e.g. `(fromInteger 256 :: Word8) == 0` without error

That's true. However, here's something you can do already now with recent GHCs which gives turns literal-overflows GHC is able to detect into hard compile errors:

$ ghci -Wall -Werror=overflowed-literals GHCi, version 8.2.1: http://www.haskell.org/ghc/ :? for help Prelude> (256 :: Data.Word.Word8) == 0

<interactive>:1:2: warning: [-Woverflowed-literals] Literal 256 is out of the GHC.Word.Word8 range 0..255

<no location info>: error: Failing due to -Werror. Prelude>

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Dominic Steinitz dominic@steinitz.org http://idontgetoutmuch.wordpress.com