The problems being: * External libraries don't do this. See: All those "header-only" libraries you see, starting back with boost * It's a total PITA once the

The problems being: * External libraries don't do this. See: All those "header-only" libraries you see, starting back with boost * It's a total PITA once the types get complicated Source: Have worked for 10 years on a large codebase with "template auto instantiation" off.