MDEV-39002 Fix CREATE TABLE Assertion

Propagate fix_attributes boolean return value to prevent Diagnostics_area assertion failures during error conditions.

Author: kjarir

mysql-test/main/mdev_39002.result

@@ -0,0 +1,2 @@
+CREATE TABLE t (a INT, b VARCHAR(8) DEFAULT (IFNULL(a,''))) CHARSET swe7;
+ERROR HY000: Illegal mix of collations (latin1_swedish_ci,NUMERIC) and (swe7_swedish_ci,COERCIBLE) for operation 'ifnull'

mysql-test/main/mdev_39002.test

@@ -0,0 +1,2 @@
+--error ER_CANT_AGGREGATE_2COLLATIONS
+CREATE TABLE t (a INT, b VARCHAR(8) DEFAULT (IFNULL(a,''))) CHARSET swe7;

sql/item_cmpfunc.h

@@ -1207,9 +1207,9 @@ class Item_func_coalesce :public Item_func_case_expression
   bool fix_length_and_dec(THD *thd) override
   {
     update_nullability_post_fix_fields();
-    if (aggregate_for_result(func_name_cstring(), args, arg_count, true))
+    if (aggregate_for_result(func_name_cstring(), args, arg_count, true) ||
+        fix_attributes(args, arg_count))
       return TRUE;
-    fix_attributes(args, arg_count);
     return FALSE;
   }
   LEX_CSTRING func_name_cstring() const override
@@ -1236,9 +1236,9 @@ class Item_func_case_abbreviation2 :public Item_func_case_expression
 protected:
   bool fix_length_and_dec2(Item **items)
   {
-    if (aggregate_for_result(func_name_cstring(), items, 2, true))
+    if (aggregate_for_result(func_name_cstring(), items, 2, true) ||
+        fix_attributes(items, 2))
       return TRUE;
-    fix_attributes(items, 2);
     return FALSE;
   }
 
@@ -1376,7 +1376,9 @@ class Item_func_if :public Item_func_case_abbreviation2_switch
   bool fix_fields(THD *, Item **) override;
   bool fix_length_and_dec(THD *thd) override
   {
-    return fix_length_and_dec2_eliminate_null(args + 1);
+    if (fix_length_and_dec2_eliminate_null(args + 1))
+      return TRUE;
+    return FALSE;
   }
   LEX_CSTRING func_name_cstring() const override
   {
@@ -1413,7 +1415,9 @@ class Item_func_nvl2 :public Item_func_case_abbreviation2_switch
   }
   bool fix_length_and_dec(THD *thd) override
   {
-    return fix_length_and_dec2_eliminate_null(args + 1);
+    if (fix_length_and_dec2_eliminate_null(args + 1))
+      return TRUE;
+    return FALSE;
   }
 
 protected: