MDEV-8865 Wrong field type or metadata for COALESCE(signed_int_column, unsigned_int_column)

Item_func_hybrid_field_type did not return correct field_type(), cmp_type()
and result_type() in some cases, because cached_result_type and
cached_field_type were set in independent pieces of the code and
did not properly match to each other.
Fix:
- Removing Item_func_hybrid_result_type
- Deriving Item_func_hybrid_field_type directly from Item_func
- Introducing a new class Type_handler which guarantees that
  field_type(), cmp_type() and result_type() are always properly synchronized
  and using the new class in Item_func_hybrid_field_type.

1 files changed, 1 insertions, 1 deletions

diff --git a/sql/item_timefunc.h b/sql/item_timefunc.h
index edc77038f89..2d02a55b16a 100644
--- a/sql/item_timefunc.h
+++ b/sql/item_timefunc.h
@@ -421,7 +421,7 @@ public:
     set_if_smaller(decimals, TIME_SECOND_PART_DIGITS);
     max_length=17 + (decimals ? decimals + 1 : 0);
     maybe_null= true;
-    cached_result_type= decimals ? DECIMAL_RESULT : INT_RESULT;
+    set_handler_by_result_type(decimals ? DECIMAL_RESULT : INT_RESULT);
   }
   double real_op() { DBUG_ASSERT(0); return 0; }
   String *str_op(String *str) { DBUG_ASSERT(0); return 0; }