I've implemented the AWS IAM engine and all policy types, conditions, etc in here if you want to try it out. It's the most thorough in terms of edge case coverage I'm aware of and I'm constantly adding enhancements and closing edge cases.

https://github.com/act-security-labs/iam-lens

It uses https://github.com/act-security-labs/iam-collect to get all the policies which includes example terraform to gather all the data at scale.