Agree, and this is a huge bungle you can make in language design, that will affect compiler performance down the line significantly.

If you know which package each type comes from, you only need to check the exports of that package, otherwise its a local.

Otherwise you have to start compilation by building up a list of every package and its exports. This is particularly bad for incremental compilation, and starts to drag on large projects.

The saving grace of .NET in this case is that most .NET programs traditionally didn't have that many imports. You have mscorlib for the framework itself, which is almost all the basics, and maybe ASP.NET and a dozen other small packages.

But this doesn't have to be the case, and if you have thousands of small packages (because your app is huge), then your performance tanks.