Fixed bug #16382.

When an ambiguous field name is used in a group by clause a warning is issued
in the find_order_in_list function by a call to push_warning_printf.
An expression that was not always valid was passed to this call as the field
name parameter.

mysql-test/r/view.result

@@ -2504,3 +2504,37 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Select tables optimized away
 DROP VIEW v1;
 DROP TABLE t1;
+CREATE TABLE t1 (x varchar(10));
+INSERT INTO t1 VALUES (null), ('foo'), ('bar'), (null);
+CREATE VIEW v1 AS SELECT * FROM t1;
+SELECT IF(x IS NULL, 'blank', 'not blank') FROM v1 GROUP BY x;
+IF(x IS NULL, 'blank', 'not blank')
+blank
+not blank
+not blank
+SELECT IF(x IS NULL, 'blank', 'not blank') AS x FROM t1 GROUP BY x;
+x
+blank
+not blank
+not blank
+Warnings:
+Warning	1052	Column 'x' in group statement is ambiguous
+SELECT IF(x IS NULL, 'blank', 'not blank') AS x FROM v1;
+x
+blank
+not blank
+not blank
+blank
+SELECT IF(x IS NULL, 'blank', 'not blank') AS y FROM v1 GROUP BY y;
+y
+blank
+not blank
+SELECT IF(x IS NULL, 'blank', 'not blank') AS x FROM v1 GROUP BY x;
+x
+blank
+not blank
+not blank
+Warnings:
+Warning	1052	Column 'x' in group statement is ambiguous
+DROP VIEW v1;
+DROP TABLE t1;

mysql-test/t/view.test

@@ -2363,3 +2363,20 @@ EXPLAIN SELECT MIN(a) FROM v1;
 
 DROP VIEW v1;
 DROP TABLE t1;
+
+#
+# Bug#16382: grouping name is resolved against a view column name
+#            which coincides with a select column name
+
+CREATE TABLE t1 (x varchar(10));
+INSERT INTO t1 VALUES (null), ('foo'), ('bar'), (null);
+CREATE VIEW v1 AS SELECT * FROM t1;
+
+SELECT IF(x IS NULL, 'blank', 'not blank') FROM v1 GROUP BY x;
+SELECT IF(x IS NULL, 'blank', 'not blank') AS x FROM t1 GROUP BY x;
+SELECT IF(x IS NULL, 'blank', 'not blank') AS x FROM v1;
+SELECT IF(x IS NULL, 'blank', 'not blank') AS y FROM v1 GROUP BY y;
+SELECT IF(x IS NULL, 'blank', 'not blank') AS x FROM v1 GROUP BY x;
+
+DROP VIEW v1;
+DROP TABLE t1;

sql/sql_select.cc

@@ -12381,7 +12381,8 @@ find_order_in_list(THD *thd, Item **ref_pointer_array, TABLE_LIST *tables,
         overshadows the column reference from the SELECT list.
       */
       push_warning_printf(thd, MYSQL_ERROR::WARN_LEVEL_WARN, ER_NON_UNIQ_ERROR,
-                          ER(ER_NON_UNIQ_ERROR), from_field->field_name,
+                          ER(ER_NON_UNIQ_ERROR),
+                          ((Item_ident*) order_item)->field_name,
                           current_thd->where);
     }
   }