Handle edge cases in import

**Problem**
When working with types, the error messages could be more descriptive.

**Suggestion**
Improve error handling and add detailed error messages.

**Context**
This would help with debugging and maintenance.

The issue does not name files, tests, or a specific failing import case. Start by locating the import handling and type-related error paths in the repository, then reproduce the edge cases described by the issue; done means the relevant failures produce more detailed, useful error messages and the behavior is covered by tests.

Written by the indexing model from the issue text.