I don't think that's the case. Template Haskell lets you generate Haskell code at compile time, including by doing arbitrary IO. This is technically unsafe but

I don't think that's the case. Template Haskell lets you generate Haskell code at compile time, including by doing arbitrary IO. This is technically unsafe but is usually okay because you're only reading local files and so forth. It's occasionally really useful for generating things like database mappings, lenses, etc.