FKs with 'ON UPDATE CASCADE' can be set in some contexts but not others

First of all - sorry if this should be a comment on the related ticket as opposed to its own ticket; however my report goes further (/has a wider issue than the original report / causes problems with backups); so I believed best to raise as its own ticket.

As per MDEV-30606, trying to create a table with a FK that has ON UPDATE CASCADE and a CHECK CONSTRAINT returns the (slightly unhelpful) error message: Function or expression %s cannot be used in the CHECK clause of %s. (It would be useful if this error was less generic for the use case, as it is known that the referred column is not a function or expression - but the error makes it seem like you have used the wrong column name).

However running `ALTER TABLE` lets you add the constraint without issue (and then the `CREATE TABLE` statement will fail, breaking restoring backups or copying the table/etc).

Test Script:

# Setup

CREATE OR REPLACE TABLE `x1` (

	`a` INT NOT NULL, 

	PRIMARY KEY(`a`)

);

# Fails with 'Function or expression 'b' cannot be used in the CHECK clause of `b-2`'

CREATE OR REPLACE TABLE `x2` (

	`b` INT NULL,  

	CONSTRAINT FOREIGN KEY(`b`) REFERENCES `x1`(`a`) ON UPDATE CASCADE, 

	CONSTRAINT CHECK (`b` > 1)

);

# Succeeds

CREATE OR REPLACE TABLE `x2` (

	`b` INT NULL,  

	CONSTRAINT FOREIGN KEY(`b`) REFERENCES `x1`(`a`) ON UPDATE CASCADE

);

ALTER TABLE `x2` ADD CONSTRAINT CHECK (`b` > 1);

# Then:

SHOW CREATE TABLE `x2`;

/* Outputs, but running this will error as per the initial create command

CREATE TABLE `x2` (

  `b` int(11) DEFAULT NULL,

  KEY `b` (`b`),

  CONSTRAINT `x2_ibfk_1` FOREIGN KEY (`b`) REFERENCES `x1` (`a`) ON UPDATE CASCADE,

  CONSTRAINT `CONSTRAINT_1` CHECK (`b` > 1)

) ENGINE=InnoDB DEFAULT CHARSET=utf8mb3 COLLATE=utf8mb3_general_ci

*/