PostgreSQL query to rename and change column type with single query

In PostgreSQL, ALTER TABLE can take a series of operations. So:

ALTER TABLE <tablename> RENAME <oldcolumn> TO <newcolumn>;
ALTER TABLE <tablename> ALTER COLUMN <columnname> TYPE <newtype>;

is the same as

ALTER TABLE <tablename> 
  ALTER COLUMN <columnname> TYPE <newtype>
  RENAME <oldcolumn> TO <newcolumn>;

However... why? IIRC the rename won't cause a full-table scan, so there's no benefit over just doing the two statements separately, within one transaction. What problem are you actually trying to solve with this?

PostgreSQL: Alter table column name and data-type:

ALTER TABLE <TableName> 
   ALTER [ COLUMN ] column [ SET DATA ] TYPE data_type [ COLLATE collation ] [ USING expression ]
  RENAME [ COLUMN ] column TO new_column;

See ALTER TABLE.