a2f303ad09
Various miscellaneous changes pushing towards HRTB support: 1. Update parser and adjust ast to support `for<'a,'b>` syntax, both in closures and trait bounds. Warn on the old syntax (not error, for stage0). 2. Refactor TyTrait representation to include a TraitRef. 3. Purge `once_fns` feature gate and `once` keyword. r? @pcwalton This is a [breaking-change]: - The `once_fns` feature is now officially deprecated. Rewrite using normal closures or unboxed closures. - The new `for`-based syntax now issues warnings (but not yet errors): - `fn<'a>(T) -> U` becomes `for<'a> fn(T) -> U` - `<'a> |T| -> U` becomes `for<'a> |T| -> U`