Revert "Fix `impl_trait` function to emit correct ast" This reverts commit 55a4813151a8f36dcdb520c45a461fe5dfbed499. Fix `impl_def_from_trait` It now generates the correct `ast::Impl` using `generate_trait_impl_text` and parses it to form the right node (copied from the private fn 'make::ast_from_text').