My developer has created a custom class to extend the datasource.connection class and when he hits SAVE, gets the followin error message:

EROR: Compile Error? Type not visible: DataSource.Connection at line 5 column 15.

Line 5 states:
global class  TestUserDataSourceConnection extends DataSource.Connection {

Problem at botton says: Line 5 Type is not visible: DataSource.Connection

Any ideas what may causing the error?

We'd like to find out our options to reach out to our ERP on demand.   When we pull up an account, we need to know in real time if an account is on credit hold.  We don't need a full integration, just this one piece.  The data won't store in SF, we just need to have a flag showing that an account is on Credit Hold per our ERP (MAS 500).
We just don't know (1) is it possible and (2) what approach to take.   We would like some guidance.
 

My developer has created a custom class to extend the datasource.connection class and when he hits SAVE, gets the followin error message:

EROR: Compile Error? Type not visible: DataSource.Connection at line 5 column 15.

Line 5 states:
global class  TestUserDataSourceConnection extends DataSource.Connection {

Problem at botton says: Line 5 Type is not visible: DataSource.Connection

Any ideas what may causing the error?