fix: Synthesus should use SafeLookup constraint.

Author: mchav

app/Synthesis.hs

@@ -86,11 +86,11 @@ main = do
 
 clean ::
     ( DT.AssertPresent "Ticket" cols
-    , DT.Lookup "Ticket" cols ~ Maybe T.Text
+    , DT.SafeLookup "Ticket" cols ~ Maybe T.Text
     , DT.AssertPresent "Name" cols
-    , DT.Lookup "Name" cols ~ Maybe T.Text
+    , DT.SafeLookup "Name" cols ~ Maybe T.Text
     , DT.AssertPresent "Cabin" cols
-    , DT.Lookup "Cabin" cols ~ Maybe T.Text
+    , DT.SafeLookup "Cabin" cols ~ Maybe T.Text
     ) =>
     DT.TypedDataFrame cols ->
     DT.TypedDataFrame

src/DataFrame/Typed/Schema.hs

@@ -77,9 +77,10 @@ type family Lookup (name :: Symbol) (cols :: [Type]) :: Type where
         TypeError
             ('Text "Column '" ':<>: 'Text name ':<>: 'Text "' not found in schema")
 
--- | Like 'Lookup', but returns a harmless fallback ('Int') instead of
--- 'TypeError' when the column is not found.  Use together with
--- 'AssertPresent' so the error fires exactly once.
+{- | Like 'Lookup', but returns a harmless fallback ('Int') instead of
+'TypeError' when the column is not found.  Use together with
+'AssertPresent' so the error fires exactly once.
+-}
 type family SafeLookup (name :: Symbol) (cols :: [Type]) :: Type where
     SafeLookup name (Column name a ': _) = a
     SafeLookup name (Column _ _ ': rest) = SafeLookup name rest