> we had for instance a library for interacting with a particular service that was generated from an XML schema, making the code perfectly type-safe, with different functions for each datatype. In many languages that allow compile-time metaprogramming, like C++ and D, IO cannot be performed at compile time, so such schema-driven code generation would not be possible.

Actually this would be possible in D since you can read files at compile-time with the "import(filename)" syntax. Then you can use compile-time parser generators to parse it.