expanding type synonyms in error messages
Ömer Sinan Ağacan
omeragacan at gmail.com
Tue Jun 16 15:20:51 UTC 2015
While working with complex types with lots of arguments etc. errors are
becoming annoying very fast. For example, GHC prints errors in this way:
Expected type: <type without any synonyms>
Actual type: <type with synonyms>
Now I have to expand that synonym in my head to understand the error.
I was wondering if implementing something like this is possible:
In type error messages, GHC also prints types that are cleaned from type
synonyms. Maybe something like this:
Expected type: <type1>
(without synonyms): <type1, synonyms are expanded>
Actual type: <type2>
(without synonyms): <type2, synonyms are expanded>
If this is not always desirable for some reason, we can hide this behavior
behind a flag.
What do GHC devs think about this? Is this, in theory, possible to do? How hard
would it be to implement this?
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