Emit a warning for non-fully-initialized records

Non-initialized record fields make it easy to accidentally introduce nondeterminism. Consider the following Curry example, which emits no warnings or errors:

data X = X { n :: Int, m :: Bool }

mkX :: X
mkX = X { n = 3 }

test :: Bool
test = not $ m mkX -- whoops

Since uninitialized fields (like m in this case) are interpreted as free variables in Curry, test evaluates to False and True nondeterministically.

Even if this is what the user intends, making it explicit might be better style:

data X = X { n :: Int, m :: Bool }

mkX :: X
mkX = X { n = 3, m = m' }
    where m' free

test :: Bool
test = not $ m mkX -- whoops

It would therefore be nice to have a warning message, perhaps similar to the one that GHC emits:

NonFullyInitializedRecord.hs:4:7: warning: [-Wmissing-fields]
    • Fields of ‘X’ not initialised:
        m :: Int
    • In the expression: X {n = 3}
      In an equation for ‘mkX’: mkX = X {n = 3}
  |
4 | mkX = X { n = 3 }
  |

If #92 would get integrated at some point, the compiler could potentially generate a quick fix for making the free fields explicit, similar to the example above.