auto merge of #18743 : nikomatsakis/rust/hrtb-refactor-2, r=pcwalton

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`

2 files changed, 13 insertions, 6 deletions

diff --git a/src/libsyntax/ext/build.rs b/src/libsyntax/ext/build.rs
index 5921d630b89..862cbf3d7ca 100644
--- a/src/libsyntax/ext/build.rs
+++ b/src/libsyntax/ext/build.rs
@@ -68,10 +68,11 @@ pub trait AstBuilder {
                span: Span,
                id: ast::Ident,
                bounds: OwnedSlice<ast::TyParamBound>,
-               unbound: Option<ast::TyParamBound>,
+               unbound: Option<ast::TraitRef>,
                default: Option<P<ast::Ty>>) -> ast::TyParam;
 
     fn trait_ref(&self, path: ast::Path) -> ast::TraitRef;
+    fn poly_trait_ref(&self, path: ast::Path) -> ast::PolyTraitRef;
     fn typarambound(&self, path: ast::Path) -> ast::TyParamBound;
     fn lifetime(&self, span: Span, ident: ast::Name) -> ast::Lifetime;
     fn lifetime_def(&self,
@@ -417,7 +418,7 @@ impl<'a> AstBuilder for ExtCtxt<'a> {
                span: Span,
                id: ast::Ident,
                bounds: OwnedSlice<ast::TyParamBound>,
-               unbound: Option<ast::TyParamBound>,
+               unbound: Option<ast::TraitRef>,
                default: Option<P<ast::Ty>>) -> ast::TyParam {
         ast::TyParam {
             ident: id,
@@ -445,12 +446,18 @@ impl<'a> AstBuilder for ExtCtxt<'a> {
         ast::TraitRef {
             path: path,
             ref_id: ast::DUMMY_NODE_ID,
-            lifetimes: Vec::new(),
+        }
+    }
+
+    fn poly_trait_ref(&self, path: ast::Path) -> ast::PolyTraitRef {
+        ast::PolyTraitRef {
+            bound_lifetimes: Vec::new(),
+            trait_ref: self.trait_ref(path)
         }
     }
 
     fn typarambound(&self, path: ast::Path) -> ast::TyParamBound {
-        ast::TraitTyParamBound(self.trait_ref(path))
+        ast::TraitTyParamBound(self.poly_trait_ref(path))
     }
 
     fn lifetime(&self, span: Span, name: ast::Name) -> ast::Lifetime {
diff --git a/src/libsyntax/ext/deriving/generic/ty.rs b/src/libsyntax/ext/deriving/generic/ty.rs
index a90618a30b6..1ec1e3b1224 100644
--- a/src/libsyntax/ext/deriving/generic/ty.rs
+++ b/src/libsyntax/ext/deriving/generic/ty.rs
@@ -194,7 +194,7 @@ impl<'a> Ty<'a> {
 
 
 fn mk_ty_param(cx: &ExtCtxt, span: Span, name: &str,
-               bounds: &[Path], unbound: Option<ast::TyParamBound>,
+               bounds: &[Path], unbound: Option<ast::TraitRef>,
                self_ident: Ident, self_generics: &Generics) -> ast::TyParam {
     let bounds =
         bounds.iter().map(|b| {
@@ -220,7 +220,7 @@ fn mk_generics(lifetimes: Vec<ast::LifetimeDef>, ty_params: Vec<ast::TyParam>)
 #[deriving(Clone)]
 pub struct LifetimeBounds<'a> {
     pub lifetimes: Vec<(&'a str, Vec<&'a str>)>,
-    pub bounds: Vec<(&'a str, Option<ast::TyParamBound>, Vec<Path<'a>>)>,
+    pub bounds: Vec<(&'a str, Option<ast::TraitRef>, Vec<Path<'a>>)>,
 }
 
 impl<'a> LifetimeBounds<'a> {