I go farther, all told. I think any sort of diagram should almost certainly be process/pipeline based. Parts can be generated by a declarative markup, certainly. But you need a pipeline to "hand tune" things or you will end with diagrams that are clearly generated by a program. Fine for some things, sure. But there is a reason most of the diagrams that you remember the looks of were bespoke authored in a much more graphical environment.
If this was used as a generator, you could include actual type names, godoc comments (on mouse over for smarter image formats), etc. In this case, it's the fact that the rest of the code could provide context.
I go farther, all told. I think any sort of diagram should almost certainly be process/pipeline based. Parts can be generated by a declarative markup, certainly. But you need a pipeline to "hand tune" things or you will end with diagrams that are clearly generated by a program. Fine for some things, sure. But there is a reason most of the diagrams that you remember the looks of were bespoke authored in a much more graphical environment.