Multi-part `ALTER TABLE` statements can't reference columns added in the same statement.

[nicktobey]

This works in MySQL (and in the GMS in-memory DB):

create table t1(pk int primary key);
alter table t1 add column b int, add column c int as (b+1);

But trying it in Dolt results in an error:

column "b" could not be found in any table in scope

Most likely this happens because we attempt to resolve all parts of the statement before any of the new columns are added.