ceylon/ceylon-compiler — comment on commit d6c13b39cc8e66f663368161872403bf45f20e3e
File:  line 0
By quintesse:

Sure, but how many parameters are we talking about? Maybe in the end it turns out to be silly, but right now it's impossible to create a type parameter without having a TypeParameter and the builders are made to be independent code builders, otherwise we could just have continued using the Transformers.
I'm not saying we should blindly adhere to the no-tree-no-model meme, but now you're changing it because of a perceived problem in the future. Better to wait until that moment comes and decide if it's worth it keeping this "independence" or that it would just be too much trouble for a almost no benefit.
You have to think that there is NO code in the transformers anymore that generates it own classes or own methods and that's because we have the builders, we use them even in those cases that we don't *have* a Class or a Method, that's the benefit of decoupling them.
In the mean time we can have helper methods so you can easily pass a Tree.TypeParameter and not having to disassemble anything.