[tel]

Haskell has some typesafe template languages. I'm not a huge fan of them, tbh, as they're kind of rough at the moment.

More promising in my opinion is the fact that Javascript is becoming an increasingly popular backend for Haskell via GHCjs which will give a great space for building type-checked front ends which have all the guarantees you like. For instance, type checked routes already exist which prevent you from writing the wrong endpoints or sending invalid typed data to them... these can be transparently extended to the frontend without much more difficulty.