MDEV-31601 Some ALTER TABLEs fail ... with a wrong error message

Report correct algorithm in the error message.

mysql-test/main/alter_table_online.result

@@ -206,3 +206,16 @@ drop table t;
 create table t (a int, b int, c char(8), key(a,b,c));
 alter table t modify c int auto_increment key, algorithm=copy;
 drop table t;
+# MDEV-31601 Some ALTER TABLE .. fail when they worked before, and with
+# a wrong error message
+create table t (a int) engine=aria;
+insert into t values (1),(2);
+alter table t algorithm=nocopy, order by a;
+ERROR 0A000: ALGORITHM=NOCOPY is not supported for this operation. Try ALGORITHM=COPY
+alter table t engine=myisam, algorithm=inplace;
+ERROR 0A000: ALGORITHM=INPLACE is not supported for this operation. Try ALGORITHM=COPY
+drop table t;
+create temporary table t (f int);
+alter table t force, algorithm=instant;
+ERROR 0A000: ALGORITHM=INSTANT is not supported for this operation. Try ALGORITHM=COPY
+drop table t;

mysql-test/main/alter_table_online.test

@@ -207,3 +207,18 @@ drop table t;
 create table t (a int, b int, c char(8), key(a,b,c));
 alter table t modify c int auto_increment key, algorithm=copy;
 drop table t;
+
+--echo # MDEV-31601 Some ALTER TABLE .. fail when they worked before, and with
+--echo # a wrong error message
+create table t (a int) engine=aria;
+insert into t values (1),(2);
+--error ER_ALTER_OPERATION_NOT_SUPPORTED
+alter table t algorithm=nocopy, order by a;
+--error ER_ALTER_OPERATION_NOT_SUPPORTED
+alter table t engine=myisam, algorithm=inplace;
+drop table t;
+
+create temporary table t (f int);
+--error ER_ALTER_OPERATION_NOT_SUPPORTED
+alter table t force, algorithm=instant;
+drop table t;

mysql-test/main/mysql57_virtual.result

@@ -14,7 +14,7 @@ a	b	c
 1	2	4
 2	3	5
 alter online table mysql57_virtual comment "I am now a MariaDB table", algorithm=nocopy;
-ERROR 0A000: ALGORITHM=INPLACE is not supported for this operation. Try ALGORITHM=COPY
+ERROR 0A000: ALGORITHM=NOCOPY is not supported for this operation. Try ALGORITHM=COPY
 alter table mysql57_virtual comment "I am now a MariaDB table";
 SHOW CREATE TABLE mysql57_virtual;
 Table	Create Table

sql/sql_table.cc

@@ -10690,7 +10690,7 @@ do_continue:;
     if (alter_info->algorithm_is_nocopy(thd))
     {
       my_error(ER_ALTER_OPERATION_NOT_SUPPORTED, MYF(0),
-               "ALGORITHM=INPLACE", "ALGORITHM=COPY");
+               alter_info->algorithm_clause(thd), "ALGORITHM=COPY");
       DBUG_RETURN(true);
     }