First of all, Value is a nicer name than Single. However the main reason is to avoid error calls and to get better feedback about the code from GHC. Because of the GHC bug #6124, we had many calls to 'error' just to avoid spurious warnings. By using data (instead of newtype) for Value we're able to avoid them. This commit removes *19* error calls from Sql.hs that GHC is now able to prove that are unreachable. |
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| Test.hs | ||