[Haskell-cafe] incomplete-uni-patterns

Thomas Jakway thomasjakway1 at gmail.com
Fri Jan 27 03:02:34 UTC 2023

Just a miscellaneous Haskell user, but that also sounds good to me.

I definitely support having a way to tell the compiler at the most 
specific level possible (per line, in this case) that the author is 
intentionally doing this and not to warn about it.

I wrote in scala for years and was always unhappy that for a very long 
time the designers refused to support [1] ( a scala version of Java's 
@SuppressWarnings annotation. The suggested hack for about a decade was 
to use a compiler plugin.


Unrelated/on the importance of warning about the right things:

Thinking about this made me remember that C's switch 
fall-through-by-default behavior is so bad that you need to tell the 
compiler you actually want to do that. [2] [3]


[2] https://learn.microsoft.com/en-us/cpp/code-quality/c26819?view=msvc-170

[3] https://en.cppreference.com/w/c/language/attributes/fallthrough

On 1/25/23 21:24, Kazu Yamamoto (山本和彦) via Haskell-Cafe wrote:
> Hi David,
>> It seems to me that instead of working around this, we should add a pragma
>> to suppress the warning at the pattern site. Maybe something like
>> let
>>    {-# PARTIAL_MATCH #-}
>>    Just a = blah blah
>> That way GHC can see that you noticed the partial match and that you're
>> okay with it.
> This sounds lovely to me!
> --Kazu
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