On collectOnClauses, match from clauses in the correct order.

Previously it tried matching on the right branch just after
matching on the current node, which means that on the default
right fixity everything was reversed.

Note: SQLite didn't give any error messages for this bug!

src/Database/Esqueleto/Internal/Sql.hs

@@ -85,11 +85,14 @@ collectOnClauses = go []
         Nothing -> (f:) <$> findMatching acc expr
     findMatching [] expr = Left expr
 
-    tryMatch expr (FromJoin l k r Nothing) =
-      return (FromJoin l k r (Just expr))
-    tryMatch expr (FromJoin l k r j@(Just _)) =
-      ((\r' -> FromJoin l k r' j) <$> tryMatch expr r) `mplus`
-      ((\l' -> FromJoin l' k r j) <$> tryMatch expr l)
+    tryMatch expr (FromJoin l k r onClause) =
+      matchR `mplus` matchC `mplus` matchL -- right to left
+        where
+          matchR = (\r' -> FromJoin l k r' onClause) <$> tryMatch expr r
+          matchL = (\l' -> FromJoin l' k r onClause) <$> tryMatch expr l
+          matchC = case onClause of
+                     Nothing -> return (FromJoin l k r (Just expr))
+                     Just _  -> mzero
     tryMatch _ _ = mzero