libsyntax: use unboxed closures

32 files changed, 377 insertions, 245 deletions

diff --git a/src/libsyntax/ast_map/blocks.rs b/src/libsyntax/ast_map/blocks.rs
index 639a33a8063..75f69f2f6d0 100644
--- a/src/libsyntax/ast_map/blocks.rs
+++ b/src/libsyntax/ast_map/blocks.rs
@@ -181,22 +181,23 @@ impl<'a> FnLikeNode<'a> {
     }
 
     pub fn kind(self) -> visit::FnKind<'a> {
-        let item = |p: ItemFnParts<'a>| -> visit::FnKind<'a> {
+        let item = |: p: ItemFnParts<'a>| -> visit::FnKind<'a> {
             visit::FkItemFn(p.ident, p.generics, p.style, p.abi)
         };
-        let closure = |_: ClosureParts| {
+        let closure = |: _: ClosureParts| {
             visit::FkFnBlock
         };
-        let method = |m: &'a ast::Method| {
+        let method = |: m: &'a ast::Method| {
             visit::FkMethod(m.pe_ident(), m.pe_generics(), m)
         };
         self.handle(item, method, closure)
     }
 
-    fn handle<A>(self,
-                 item_fn: |ItemFnParts<'a>| -> A,
-                 method: |&'a ast::Method| -> A,
-                 closure: |ClosureParts<'a>| -> A) -> A {
+    fn handle<A, I, M, C>(self, item_fn: I, method: M, closure: C) -> A where
+        I: FnOnce(ItemFnParts<'a>) -> A,
+        M: FnOnce(&'a ast::Method) -> A,
+        C: FnOnce(ClosureParts<'a>) -> A,
+    {
         match self.node {
             ast_map::NodeItem(i) => match i.node {
                 ast::ItemFn(ref decl, style, abi, ref generics, ref block) =>
diff --git a/src/libsyntax/ast_map/mod.rs b/src/libsyntax/ast_map/mod.rs
index 2c985f403f8..907ac6b19fc 100644
--- a/src/libsyntax/ast_map/mod.rs
+++ b/src/libsyntax/ast_map/mod.rs
@@ -424,7 +424,9 @@ impl<'ast> Map<'ast> {
         }
     }
 
-    pub fn with_path<T>(&self, id: NodeId, f: |PathElems| -> T) -> T {
+    pub fn with_path<T, F>(&self, id: NodeId, f: F) -> T where
+        F: FnOnce(PathElems) -> T,
+    {
         self.with_path_next(id, None, f)
     }
 
@@ -438,7 +440,9 @@ impl<'ast> Map<'ast> {
         })
     }
 
-    fn with_path_next<T>(&self, id: NodeId, next: LinkedPath, f: |PathElems| -> T) -> T {
+    fn with_path_next<T, F>(&self, id: NodeId, next: LinkedPath, f: F) -> T where
+        F: FnOnce(PathElems) -> T,
+    {
         let parent = self.get_parent(id);
         let parent = match self.find_entry(id) {
             Some(EntryForeignItem(..)) | Some(EntryVariant(..)) => {
@@ -470,7 +474,9 @@ impl<'ast> Map<'ast> {
 
     /// Given a node ID and a closure, apply the closure to the array
     /// of attributes associated with the AST corresponding to the Node ID
-    pub fn with_attrs<T>(&self, id: NodeId, f: |Option<&[Attribute]>| -> T) -> T {
+    pub fn with_attrs<T, F>(&self, id: NodeId, f: F) -> T where
+        F: FnOnce(Option<&[Attribute]>) -> T,
+    {
         let attrs = match self.get(id) {
             NodeItem(i) => Some(i.attrs.as_slice()),
             NodeForeignItem(fi) => Some(fi.attrs.as_slice()),
diff --git a/src/libsyntax/ast_util.rs b/src/libsyntax/ast_util.rs
index eec3f69ee64..7579972c6d8 100644
--- a/src/libsyntax/ast_util.rs
+++ b/src/libsyntax/ast_util.rs
@@ -602,6 +602,7 @@ pub fn compute_id_range_for_fn_body(fk: visit::FnKind,
     id_visitor.operation.result
 }
 
+// FIXME(#19596) unbox `it`
 pub fn walk_pat(pat: &Pat, it: |&Pat| -> bool) -> bool {
     if !it(pat) {
         return false;
@@ -632,21 +633,21 @@ pub fn walk_pat(pat: &Pat, it: |&Pat| -> bool) -> bool {
 }
 
 pub trait EachViewItem {
-    fn each_view_item(&self, f: |&ast::ViewItem| -> bool) -> bool;
+    fn each_view_item<F>(&self, f: F) -> bool where F: FnMut(&ast::ViewItem) -> bool;
 }
 
-struct EachViewItemData<'a> {
-    callback: |&ast::ViewItem|: 'a -> bool,
+struct EachViewItemData<F> where F: FnMut(&ast::ViewItem) -> bool {
+    callback: F,
 }
 
-impl<'a, 'v> Visitor<'v> for EachViewItemData<'a> {
+impl<'v, F> Visitor<'v> for EachViewItemData<F> where F: FnMut(&ast::ViewItem) -> bool {
     fn visit_view_item(&mut self, view_item: &ast::ViewItem) {
         let _ = (self.callback)(view_item);
     }
 }
 
 impl EachViewItem for ast::Crate {
-    fn each_view_item(&self, f: |&ast::ViewItem| -> bool) -> bool {
+    fn each_view_item<F>(&self, f: F) -> bool where F: FnMut(&ast::ViewItem) -> bool {
         let mut visit = EachViewItemData {
             callback: f,
         };
diff --git a/src/libsyntax/attr.rs b/src/libsyntax/attr.rs
index 5894a88ece6..8248eae4b8c 100644
--- a/src/libsyntax/attr.rs
+++ b/src/libsyntax/attr.rs
@@ -115,7 +115,8 @@ impl AttrMetaMethods for P<MetaItem> {
 
 pub trait AttributeMethods {
     fn meta<'a>(&'a self) -> &'a MetaItem;
-    fn with_desugared_doc<T>(&self, f: |&Attribute| -> T) -> T;
+    fn with_desugared_doc<T, F>(&self, f: F) -> T where
+        F: FnOnce(&Attribute) -> T;
 }
 
 impl AttributeMethods for Attribute {
@@ -127,7 +128,9 @@ impl AttributeMethods for Attribute {
     /// Convert self to a normal #[doc="foo"] comment, if it is a
     /// comment like `///` or `/** */`. (Returns self unchanged for
     /// non-sugared doc attributes.)
-    fn with_desugared_doc<T>(&self, f: |&Attribute| -> T) -> T {
+    fn with_desugared_doc<T, F>(&self, f: F) -> T where
+        F: FnOnce(&Attribute) -> T,
+    {
         if self.node.is_sugared_doc {
             let comment = self.value_str().unwrap();
             let meta = mk_name_value_item_str(
diff --git a/src/libsyntax/codemap.rs b/src/libsyntax/codemap.rs
index 7f2becf8201..d2fe667339c 100644
--- a/src/libsyntax/codemap.rs
+++ b/src/libsyntax/codemap.rs
@@ -568,7 +568,9 @@ impl CodeMap {
         ExpnId(expansions.len().to_u32().expect("too many ExpnInfo's!") - 1)
     }
 
-    pub fn with_expn_info<T>(&self, id: ExpnId, f: |Option<&ExpnInfo>| -> T) -> T {
+    pub fn with_expn_info<T, F>(&self, id: ExpnId, f: F) -> T where
+        F: FnOnce(Option<&ExpnInfo>) -> T,
+    {
         match id {
             NO_EXPANSION => f(None),
             ExpnId(i) => f(Some(&(*self.expansions.borrow())[i as uint]))
diff --git a/src/libsyntax/config.rs b/src/libsyntax/config.rs
index 4f718555d53..87426dce918 100644
--- a/src/libsyntax/config.rs
+++ b/src/libsyntax/config.rs
@@ -19,8 +19,8 @@ use util::small_vector::SmallVector;
 
 /// A folder that strips out items that do not belong in the current
 /// configuration.
-struct Context<'a> {
-    in_cfg: |attrs: &[ast::Attribute]|: 'a -> bool,
+struct Context<F> where F: FnMut(&[ast::Attribute]) -> bool {
+    in_cfg: F,
 }
 
 // Support conditional compilation by transforming the AST, stripping out
@@ -30,7 +30,7 @@ pub fn strip_unconfigured_items(diagnostic: &SpanHandler, krate: ast::Crate) ->
     strip_items(krate, |attrs| in_cfg(diagnostic, config.as_slice(), attrs))
 }
 
-impl<'a> fold::Folder for Context<'a> {
+impl<F> fold::Folder for Context<F> where F: FnMut(&[ast::Attribute]) -> bool {
     fn fold_mod(&mut self, module: ast::Mod) -> ast::Mod {
         fold_mod(self, module)
     }
@@ -54,16 +54,20 @@ impl<'a> fold::Folder for Context<'a> {
     }
 }
 
-pub fn strip_items(krate: ast::Crate,
-                   in_cfg: |attrs: &[ast::Attribute]| -> bool)
-                   -> ast::Crate {
+pub fn strip_items<F>(krate: ast::Crate, in_cfg: F) -> ast::Crate where
+    F: FnMut(&[ast::Attribute]) -> bool,
+{
     let mut ctxt = Context {
         in_cfg: in_cfg,
     };
     ctxt.fold_crate(krate)
 }
 
-fn filter_view_item(cx: &mut Context, view_item: ast::ViewItem) -> Option<ast::ViewItem> {
+fn filter_view_item<F>(cx: &mut Context<F>,
+                       view_item: ast::ViewItem)
+                       -> Option<ast::ViewItem> where
+    F: FnMut(&[ast::Attribute]) -> bool
+{
     if view_item_in_cfg(cx, &view_item) {
         Some(view_item)
     } else {
@@ -71,7 +75,11 @@ fn filter_view_item(cx: &mut Context, view_item: ast::ViewItem) -> Option<ast::V
     }
 }
 
-fn fold_mod(cx: &mut Context, ast::Mod {inner, view_items, items}: ast::Mod) -> ast::Mod {
+fn fold_mod<F>(cx: &mut Context<F>,
+               ast::Mod {inner,
+               view_items, items}: ast::Mod) -> ast::Mod where
+    F: FnMut(&[ast::Attribute]) -> bool
+{
     ast::Mod {
         inner: inner,
         view_items: view_items.into_iter().filter_map(|a| {
@@ -83,8 +91,11 @@ fn fold_mod(cx: &mut Context, ast::Mod {inner, view_items, items}: ast::Mod) ->
     }
 }
 
-fn filter_foreign_item(cx: &mut Context, item: P<ast::ForeignItem>)
-                       -> Option<P<ast::ForeignItem>> {
+fn filter_foreign_item<F>(cx: &mut Context<F>,
+                          item: P<ast::ForeignItem>)
+                          -> Option<P<ast::ForeignItem>> where
+    F: FnMut(&[ast::Attribute]) -> bool
+{
     if foreign_item_in_cfg(cx, &*item) {
         Some(item)
     } else {
@@ -92,8 +103,11 @@ fn filter_foreign_item(cx: &mut Context, item: P<ast::ForeignItem>)
     }
 }
 
-fn fold_foreign_mod(cx: &mut Context, ast::ForeignMod {abi, view_items, items}: ast::ForeignMod)
-                    -> ast::ForeignMod {
+fn fold_foreign_mod<F>(cx: &mut Context<F>,
+                       ast::ForeignMod {abi, view_items, items}: ast::ForeignMod)
+                       -> ast::ForeignMod where
+    F: FnMut(&[ast::Attribute]) -> bool
+{
     ast::ForeignMod {
         abi: abi,
         view_items: view_items.into_iter().filter_map(|a| {
@@ -105,7 +119,9 @@ fn fold_foreign_mod(cx: &mut Context, ast::ForeignMod {abi, view_items, items}:
     }
 }
 
-fn fold_item(cx: &mut Context, item: P<ast::Item>) -> SmallVector<P<ast::Item>> {
+fn fold_item<F>(cx: &mut Context<F>, item: P<ast::Item>) -> SmallVector<P<ast::Item>> where
+    F: FnMut(&[ast::Attribute]) -> bool
+{
     if item_in_cfg(cx, &*item) {
         SmallVector::one(item.map(|i| cx.fold_item_simple(i)))
     } else {
@@ -113,7 +129,9 @@ fn fold_item(cx: &mut Context, item: P<ast::Item>) -> SmallVector<P<ast::Item>>
     }
 }
 
-fn fold_item_underscore(cx: &mut Context, item: ast::Item_) -> ast::Item_ {
+fn fold_item_underscore<F>(cx: &mut Context<F>, item: ast::Item_) -> ast::Item_ where
+    F: FnMut(&[ast::Attribute]) -> bool
+{
     let item = match item {
         ast::ItemImpl(a, b, c, impl_items) => {
             let impl_items = impl_items.into_iter()
@@ -166,7 +184,9 @@ fn fold_item_underscore(cx: &mut Context, item: ast::Item_) -> ast::Item_ {
     fold::noop_fold_item_underscore(item, cx)
 }
 
-fn fold_struct(cx: &mut Context, def: P<ast::StructDef>) -> P<ast::StructDef> {
+fn fold_struct<F>(cx: &mut Context<F>, def: P<ast::StructDef>) -> P<ast::StructDef> where
+    F: FnMut(&[ast::Attribute]) -> bool
+{
     def.map(|ast::StructDef { fields, ctor_id }| {
         ast::StructDef {
             fields: fields.into_iter().filter(|m| {
@@ -177,7 +197,9 @@ fn fold_struct(cx: &mut Context, def: P<ast::StructDef>) -> P<ast::StructDef> {
     })
 }
 
-fn retain_stmt(cx: &mut Context, stmt: &ast::Stmt) -> bool {
+fn retain_stmt<F>(cx: &mut Context<F>, stmt: &ast::Stmt) -> bool where
+    F: FnMut(&[ast::Attribute]) -> bool
+{
     match stmt.node {
         ast::StmtDecl(ref decl, _) => {
             match decl.node {
@@ -191,7 +213,9 @@ fn retain_stmt(cx: &mut Context, stmt: &ast::Stmt) -> bool {
     }
 }
 
-fn fold_block(cx: &mut Context, b: P<ast::Block>) -> P<ast::Block> {
+fn fold_block<F>(cx: &mut Context<F>, b: P<ast::Block>) -> P<ast::Block> where
+    F: FnMut(&[ast::Attribute]) -> bool
+{
     b.map(|ast::Block {id, view_items, stmts, expr, rules, span}| {
         let resulting_stmts: Vec<P<ast::Stmt>> =
             stmts.into_iter().filter(|a| retain_stmt(cx, &**a)).collect();
@@ -212,7 +236,9 @@ fn fold_block(cx: &mut Context, b: P<ast::Block>) -> P<ast::Block> {
     })
 }
 
-fn fold_expr(cx: &mut Context, expr: P<ast::Expr>) -> P<ast::Expr> {
+fn fold_expr<F>(cx: &mut Context<F>, expr: P<ast::Expr>) -> P<ast::Expr> where
+    F: FnMut(&[ast::Attribute]) -> bool
+{
     expr.map(|ast::Expr {id, span, node}| {
         fold::noop_fold_expr(ast::Expr {
             id: id,
@@ -229,19 +255,27 @@ fn fold_expr(cx: &mut Context, expr: P<ast::Expr>) -> P<ast::Expr> {
     })
 }
 
-fn item_in_cfg(cx: &mut Context, item: &ast::Item) -> bool {
+fn item_in_cfg<F>(cx: &mut Context<F>, item: &ast::Item) -> bool where
+    F: FnMut(&[ast::Attribute]) -> bool
+{
     return (cx.in_cfg)(item.attrs.as_slice());
 }
 
-fn foreign_item_in_cfg(cx: &mut Context, item: &ast::ForeignItem) -> bool {
+fn foreign_item_in_cfg<F>(cx: &mut Context<F>, item: &ast::ForeignItem) -> bool where
+    F: FnMut(&[ast::Attribute]) -> bool
+{
     return (cx.in_cfg)(item.attrs.as_slice());
 }
 
-fn view_item_in_cfg(cx: &mut Context, item: &ast::ViewItem) -> bool {
+fn view_item_in_cfg<F>(cx: &mut Context<F>, item: &ast::ViewItem) -> bool where
+    F: FnMut(&[ast::Attribute]) -> bool
+{
     return (cx.in_cfg)(item.attrs.as_slice());
 }
 
-fn trait_method_in_cfg(cx: &mut Context, meth: &ast::TraitItem) -> bool {
+fn trait_method_in_cfg<F>(cx: &mut Context<F>, meth: &ast::TraitItem) -> bool where
+    F: FnMut(&[ast::Attribute]) -> bool
+{
     match *meth {
         ast::RequiredMethod(ref meth) => (cx.in_cfg)(meth.attrs.as_slice()),
         ast::ProvidedMethod(ref meth) => (cx.in_cfg)(meth.attrs.as_slice()),
@@ -249,7 +283,9 @@ fn trait_method_in_cfg(cx: &mut Context, meth: &ast::TraitItem) -> bool {
     }
 }
 
-fn impl_item_in_cfg(cx: &mut Context, impl_item: &ast::ImplItem) -> bool {
+fn impl_item_in_cfg<F>(cx: &mut Context<F>, impl_item: &ast::ImplItem) -> bool where
+    F: FnMut(&[ast::Attribute]) -> bool
+{
     match *impl_item {
         ast::MethodImplItem(ref meth) => (cx.in_cfg)(meth.attrs.as_slice()),
         ast::TypeImplItem(ref typ) => (cx.in_cfg)(typ.attrs.as_slice()),
diff --git a/src/libsyntax/diagnostic.rs b/src/libsyntax/diagnostic.rs
index bbda80bd96c..3a816987922 100644
--- a/src/libsyntax/diagnostic.rs
+++ b/src/libsyntax/diagnostic.rs
@@ -581,7 +581,9 @@ fn print_macro_backtrace(w: &mut EmitterWriter,
     cs.map_or(Ok(()), |call_site| print_macro_backtrace(w, cm, call_site))
 }
 
-pub fn expect<T>(diag: &SpanHandler, opt: Option<T>, msg: || -> String) -> T {
+pub fn expect<T, M>(diag: &SpanHandler, opt: Option<T>, msg: M) -> T where
+    M: FnOnce() -> String,
+{
     match opt {
         Some(t) => t,
         None => diag.handler().bug(msg().as_slice()),
diff --git a/src/libsyntax/diagnostics/plugin.rs b/src/libsyntax/diagnostics/plugin.rs
index 2be11a236d3..cb2a1f8acd8 100644
--- a/src/libsyntax/diagnostics/plugin.rs
+++ b/src/libsyntax/diagnostics/plugin.rs
@@ -25,14 +25,18 @@ thread_local!(static USED_DIAGNOSTICS: RefCell<HashMap<Name, Span>> = {
     RefCell::new(HashMap::new())
 })
 
-fn with_registered_diagnostics<T>(f: |&mut HashMap<Name, Option<Name>>| -> T) -> T {
-    REGISTERED_DIAGNOSTICS.with(|slot| {
+fn with_registered_diagnostics<T, F>(f: F) -> T where
+    F: FnOnce(&mut HashMap<Name, Option<Name>>) -> T,
+{
+    REGISTERED_DIAGNOSTICS.with(move |slot| {
         f(&mut *slot.borrow_mut())
     })
 }
 
-fn with_used_diagnostics<T>(f: |&mut HashMap<Name, Span>| -> T) -> T {
-    USED_DIAGNOSTICS.with(|slot| {
+fn with_used_diagnostics<T, F>(f: F) -> T where
+    F: FnOnce(&mut HashMap<Name, Span>) -> T,
+{
+    USED_DIAGNOSTICS.with(move |slot| {
         f(&mut *slot.borrow_mut())
     })
 }
diff --git a/src/libsyntax/ext/deriving/bounds.rs b/src/libsyntax/ext/deriving/bounds.rs
index 0595b0bc7f4..3145b3bb1a4 100644
--- a/src/libsyntax/ext/deriving/bounds.rs
+++ b/src/libsyntax/ext/deriving/bounds.rs
@@ -15,12 +15,13 @@ use ext::deriving::generic::*;
 use ext::deriving::generic::ty::*;
 use ptr::P;
 
-pub fn expand_deriving_bound(cx: &mut ExtCtxt,
-                             span: Span,
-                             mitem: &MetaItem,
-                             item: &Item,
-                             push: |P<Item>|) {
-
+pub fn expand_deriving_bound<F>(cx: &mut ExtCtxt,
+                                span: Span,
+                                mitem: &MetaItem,
+                                item: &Item,
+                                push: F) where
+    F: FnOnce(P<Item>),
+{
     let name = match mitem.node {
         MetaWord(ref tname) => {
             match tname.get() {
diff --git a/src/libsyntax/ext/deriving/clone.rs b/src/libsyntax/ext/deriving/clone.rs
index f6b8c00e761..a34764221b3 100644
--- a/src/libsyntax/ext/deriving/clone.rs
+++ b/src/libsyntax/ext/deriving/clone.rs
@@ -17,11 +17,13 @@ use ext::deriving::generic::ty::*;
 use parse::token::InternedString;
 use ptr::P;
 
-pub fn expand_deriving_clone(cx: &mut ExtCtxt,
-                             span: Span,
-                             mitem: &MetaItem,
-                             item: &Item,
-                             push: |P<Item>|) {
+pub fn expand_deriving_clone<F>(cx: &mut ExtCtxt,
+                                span: Span,
+                                mitem: &MetaItem,
+                                item: &Item,
+                                push: F) where
+    F: FnOnce(P<Item>),
+{
     let inline = cx.meta_word(span, InternedString::new("inline"));
     let attrs = vec!(cx.attribute(span, inline));
     let trait_def = TraitDef {
diff --git a/src/libsyntax/ext/deriving/cmp/eq.rs b/src/libsyntax/ext/deriving/cmp/eq.rs
index 7727bb824db..c8bf5ec326c 100644
--- a/src/libsyntax/ext/deriving/cmp/eq.rs
+++ b/src/libsyntax/ext/deriving/cmp/eq.rs
@@ -17,11 +17,13 @@ use ext::deriving::generic::ty::*;
 use parse::token::InternedString;
 use ptr::P;
 
-pub fn expand_deriving_eq(cx: &mut ExtCtxt,
-                          span: Span,
-                          mitem: &MetaItem,
-                          item: &Item,
-                          push: |P<Item>|) {
+pub fn expand_deriving_eq<F>(cx: &mut ExtCtxt,
+                             span: Span,
+                             mitem: &MetaItem,
+                             item: &Item,
+                             push: F) where
+    F: FnOnce(P<Item>),
+{
     // structures are equal if all fields are equal, and non equal, if
     // any fields are not equal or if the enum variants are different
     fn cs_eq(cx: &mut ExtCtxt, span: Span, substr: &Substructure) -> P<Expr> {
diff --git a/src/libsyntax/ext/deriving/cmp/ord.rs b/src/libsyntax/ext/deriving/cmp/ord.rs
index 1bd55b5d504..bd1962de56e 100644
--- a/src/libsyntax/ext/deriving/cmp/ord.rs
+++ b/src/libsyntax/ext/deriving/cmp/ord.rs
@@ -20,11 +20,13 @@ use ext::deriving::generic::ty::*;
 use parse::token::InternedString;
 use ptr::P;
 
-pub fn expand_deriving_ord(cx: &mut ExtCtxt,
-                           span: Span,
-                           mitem: &MetaItem,
-                           item: &Item,
-                           push: |P<Item>|) {
+pub fn expand_deriving_ord<F>(cx: &mut ExtCtxt,
+                              span: Span,
+                              mitem: &MetaItem,
+                              item: &Item,
+                              push: F) where
+    F: FnOnce(P<Item>),
+{
     macro_rules! md (
         ($name:expr, $op:expr, $equal:expr) => { {
             let inline = cx.meta_word(span, InternedString::new("inline"));
diff --git a/src/libsyntax/ext/deriving/cmp/totaleq.rs b/src/libsyntax/ext/deriving/cmp/totaleq.rs
index ecee2008254..2b986bea122 100644
--- a/src/libsyntax/ext/deriving/cmp/totaleq.rs
+++ b/src/libsyntax/ext/deriving/cmp/totaleq.rs
@@ -17,11 +17,13 @@ use ext::deriving::generic::ty::*;
 use parse::token::InternedString;
 use ptr::P;
 
-pub fn expand_deriving_totaleq(cx: &mut ExtCtxt,
-                               span: Span,
-                               mitem: &MetaItem,
-                               item: &Item,
-                               push: |P<Item>|) {
+pub fn expand_deriving_totaleq<F>(cx: &mut ExtCtxt,
+                                  span: Span,
+                                  mitem: &MetaItem,
+                                  item: &Item,
+                                  push: F) where
+    F: FnOnce(P<Item>),
+{
     fn cs_total_eq_assert(cx: &mut ExtCtxt, span: Span, substr: &Substructure) -> P<Expr> {
         cs_same_method(|cx, span, exprs| {
             // create `a.<method>(); b.<method>(); c.<method>(); ...`
diff --git a/src/libsyntax/ext/deriving/cmp/totalord.rs b/src/libsyntax/ext/deriving/cmp/totalord.rs
index 6900773f44d..a2bf46f41fc 100644
--- a/src/libsyntax/ext/deriving/cmp/totalord.rs
+++ b/src/libsyntax/ext/deriving/cmp/totalord.rs
@@ -18,11 +18,13 @@ use ext::deriving::generic::ty::*;
 use parse::token::InternedString;
 use ptr::P;
 
-pub fn expand_deriving_totalord(cx: &mut ExtCtxt,
-                                span: Span,
-                                mitem: &MetaItem,
-                                item: &Item,
-                                push: |P<Item>|) {
+pub fn expand_deriving_totalord<F>(cx: &mut ExtCtxt,
+                                   span: Span,
+                                   mitem: &MetaItem,
+                                   item: &Item,
+                                   push: F) where
+    F: FnOnce(P<Item>),
+{
     let inline = cx.meta_word(span, InternedString::new("inline"));
     let attrs = vec!(cx.attribute(span, inline));
     let trait_def = TraitDef {
diff --git a/src/libsyntax/ext/deriving/decodable.rs b/src/libsyntax/ext/deriving/decodable.rs
index e3cf2b68752..0a8d59da896 100644
--- a/src/libsyntax/ext/deriving/decodable.rs
+++ b/src/libsyntax/ext/deriving/decodable.rs
@@ -21,11 +21,13 @@ use parse::token::InternedString;
 use parse::token;
 use ptr::P;
 
-pub fn expand_deriving_decodable(cx: &mut ExtCtxt,
-                                 span: Span,
-                                 mitem: &MetaItem,
-                                 item: &Item,
-                                 push: |P<Item>|) {
+pub fn expand_deriving_decodable<F>(cx: &mut ExtCtxt,
+                                    span: Span,
+                                    mitem: &MetaItem,
+                                    item: &Item,
+                                    push: F) where
+    F: FnOnce(P<Item>),
+{
     let trait_def = TraitDef {
         span: span,
         attributes: Vec::new(),
@@ -155,12 +157,14 @@ fn decodable_substructure(cx: &mut ExtCtxt, trait_span: Span,
 /// Create a decoder for a single enum variant/struct:
 /// - `outer_pat_path` is the path to this enum variant/struct
 /// - `getarg` should retrieve the `uint`-th field with name `@str`.
-fn decode_static_fields(cx: &mut ExtCtxt,
-                        trait_span: Span,
-                        outer_pat_path: ast::Path,
-                        fields: &StaticFields,
-                        getarg: |&mut ExtCtxt, Span, InternedString, uint| -> P<Expr>)
-                        -> P<Expr> {
+fn decode_static_fields<F>(cx: &mut ExtCtxt,
+                           trait_span: Span,
+                           outer_pat_path: ast::Path,
+                           fields: &StaticFields,
+                           mut getarg: F)
+                           -> P<Expr> where
+    F: FnMut(&mut ExtCtxt, Span, InternedString, uint) -> P<Expr>,
+{
     match *fields {
         Unnamed(ref fields) => {
             let path_expr = cx.expr_path(outer_pat_path);
diff --git a/src/libsyntax/ext/deriving/default.rs b/src/libsyntax/ext/deriving/default.rs
index f4a66414d89..b3621490ce3 100644
--- a/src/libsyntax/ext/deriving/default.rs
+++ b/src/libsyntax/ext/deriving/default.rs
@@ -17,11 +17,13 @@ use ext::deriving::generic::ty::*;
 use parse::token::InternedString;
 use ptr::P;
 
-pub fn expand_deriving_default(cx: &mut ExtCtxt,
-                            span: Span,
-                            mitem: &MetaItem,
-                            item: &Item,
-                            push: |P<Item>|) {
+pub fn expand_deriving_default<F>(cx: &mut ExtCtxt,
+                                  span: Span,
+                                  mitem: &MetaItem,
+                                  item: &Item,
+                                  push: F) where
+    F: FnOnce(P<Item>),
+{
     let inline = cx.meta_word(span, InternedString::new("inline"));
     let attrs = vec!(cx.attribute(span, inline));
     let trait_def = TraitDef {
diff --git a/src/libsyntax/ext/deriving/encodable.rs b/src/libsyntax/ext/deriving/encodable.rs
index 62f3b5d01b4..30851ebeaae 100644
--- a/src/libsyntax/ext/deriving/encodable.rs
+++ b/src/libsyntax/ext/deriving/encodable.rs
@@ -97,11 +97,13 @@ use ext::deriving::generic::ty::*;
 use parse::token;
 use ptr::P;
 
-pub fn expand_deriving_encodable(cx: &mut ExtCtxt,
-                                 span: Span,
-                                 mitem: &MetaItem,
-                                 item: &Item,
-                                 push: |P<Item>|) {
+pub fn expand_deriving_encodable<F>(cx: &mut ExtCtxt,
+                                    span: Span,
+                                    mitem: &MetaItem,
+                                    item: &Item,
+                                    push: F) where
+    F: FnOnce(P<Item>),
+{
     let trait_def = TraitDef {
         span: span,
         attributes: Vec::new(),
diff --git a/src/libsyntax/ext/deriving/generic/mod.rs b/src/libsyntax/ext/deriving/generic/mod.rs
index cf3b3ad9051..a75be40604e 100644
--- a/src/libsyntax/ext/deriving/generic/mod.rs
+++ b/src/libsyntax/ext/deriving/generic/mod.rs
@@ -333,11 +333,13 @@ pub fn combine_substructure<'a>(f: CombineSubstructureFunc<'a>)
 
 
 impl<'a> TraitDef<'a> {
-    pub fn expand(&self,
-                  cx: &mut ExtCtxt,
-                  mitem: &ast::MetaItem,
-                  item: &ast::Item,
-                  push: |P<ast::Item>|) {
+    pub fn expand<F>(&self,
+                     cx: &mut ExtCtxt,
+                     mitem: &ast::MetaItem,
+                     item: &ast::Item,
+                     push: F) where
+        F: FnOnce(P<ast::Item>),
+    {
         let newitem = match item.node {
             ast::ItemStruct(ref struct_def, ref generics) => {
                 self.expand_struct_def(cx,
@@ -1309,14 +1311,16 @@ impl<'a> TraitDef<'a> {
 
 /// Fold the fields. `use_foldl` controls whether this is done
 /// left-to-right (`true`) or right-to-left (`false`).
-pub fn cs_fold(use_foldl: bool,
-               f: |&mut ExtCtxt, Span, P<Expr>, P<Expr>, &[P<Expr>]| -> P<Expr>,
-               base: P<Expr>,
-               enum_nonmatch_f: EnumNonMatchCollapsedFunc,
-               cx: &mut ExtCtxt,
-               trait_span: Span,
-               substructure: &Substructure)
-               -> P<Expr> {
+pub fn cs_fold<F>(use_foldl: bool,
+                  mut f: F,
+                  base: P<Expr>,
+                  enum_nonmatch_f: EnumNonMatchCollapsedFunc,
+                  cx: &mut ExtCtxt,
+                  trait_span: Span,
+                  substructure: &Substructure)
+                  -> P<Expr> where
+    F: FnMut(&mut ExtCtxt, Span, P<Expr>, P<Expr>, &[P<Expr>]) -> P<Expr>,
+{
     match *substructure.fields {
         EnumMatching(_, _, ref all_fields) | Struct(ref all_fields) => {
             if use_foldl {
@@ -1355,12 +1359,14 @@ pub fn cs_fold(use_foldl: bool,
 ///              self_2.method(__arg_1_2, __arg_2_2)])
 /// ```
 #[inline]
-pub fn cs_same_method(f: |&mut ExtCtxt, Span, Vec<P<Expr>>| -> P<Expr>,
-                      enum_nonmatch_f: EnumNonMatchCollapsedFunc,
-                      cx: &mut ExtCtxt,
-                      trait_span: Span,
-                      substructure: &Substructure)
-                      -> P<Expr> {
+pub fn cs_same_method<F>(f: F,
+                         enum_nonmatch_f: EnumNonMatchCollapsedFunc,
+                         cx: &mut ExtCtxt,
+                         trait_span: Span,
+                         substructure: &Substructure)
+                         -> P<Expr> where
+    F: FnOnce(&mut ExtCtxt, Span, Vec<P<Expr>>) -> P<Expr>,
+{
     match *substructure.fields {
         EnumMatching(_, _, ref all_fields) | Struct(ref all_fields) => {
             // call self_n.method(other_1_n, other_2_n, ...)
@@ -1388,14 +1394,16 @@ pub fn cs_same_method(f: |&mut ExtCtxt, Span, Vec<P<Expr>>| -> P<Expr>,
 /// fields. `use_foldl` controls whether this is done left-to-right
 /// (`true`) or right-to-left (`false`).
 #[inline]
-pub fn cs_same_method_fold(use_foldl: bool,
-                           f: |&mut ExtCtxt, Span, P<Expr>, P<Expr>| -> P<Expr>,
-                           base: P<Expr>,
-                           enum_nonmatch_f: EnumNonMatchCollapsedFunc,
-                           cx: &mut ExtCtxt,
-                           trait_span: Span,
-                           substructure: &Substructure)
-                           -> P<Expr> {
+pub fn cs_same_method_fold<F>(use_foldl: bool,
+                              mut f: F,
+                              base: P<Expr>,
+                              enum_nonmatch_f: EnumNonMatchCollapsedFunc,
+                              cx: &mut ExtCtxt,
+                              trait_span: Span,
+                              substructure: &Substructure)
+                              -> P<Expr> where
+    F: FnMut(&mut ExtCtxt, Span, P<Expr>, P<Expr>) -> P<Expr>,
+{
     cs_same_method(
         |cx, span, vals| {
             if use_foldl {
diff --git a/src/libsyntax/ext/deriving/hash.rs b/src/libsyntax/ext/deriving/hash.rs
index b7f11c25825..4e59124a129 100644
--- a/src/libsyntax/ext/deriving/hash.rs
+++ b/src/libsyntax/ext/deriving/hash.rs
@@ -17,11 +17,13 @@ use ext::deriving::generic::ty::*;
 use parse::token::InternedString;
 use ptr::P;
 
-pub fn expand_deriving_hash(cx: &mut ExtCtxt,
-                            span: Span,
-                            mitem: &MetaItem,
-                            item: &Item,
-                            push: |P<Item>|) {
+pub fn expand_deriving_hash<F>(cx: &mut ExtCtxt,
+                               span: Span,
+                               mitem: &MetaItem,
+                               item: &Item,
+                               push: F) where
+    F: FnOnce(P<Item>),
+{
 
     let (path, generics, args) = if cx.ecfg.deriving_hash_type_parameter {
         (Path::new_(vec!("std", "hash", "Hash"), None,
diff --git a/src/libsyntax/ext/deriving/primitive.rs b/src/libsyntax/ext/deriving/primitive.rs
index cd2d98b70f1..8abd846373a 100644
--- a/src/libsyntax/ext/deriving/primitive.rs
+++ b/src/libsyntax/ext/deriving/primitive.rs
@@ -18,11 +18,13 @@ use ext::deriving::generic::ty::*;
 use parse::token::InternedString;
 use ptr::P;
 
-pub fn expand_deriving_from_primitive(cx: &mut ExtCtxt,
-                                      span: Span,
-                                      mitem: &MetaItem,
-                                      item: &Item,
-                                      push: |P<Item>|) {
+pub fn expand_deriving_from_primitive<F>(cx: &mut ExtCtxt,
+                                         span: Span,
+                                         mitem: &MetaItem,
+                                         item: &Item,
+                                         push: F) where
+    F: FnOnce(P<Item>),
+{
     let inline = cx.meta_word(span, InternedString::new("inline"));
     let attrs = vec!(cx.attribute(span, inline));
     let trait_def = TraitDef {
diff --git a/src/libsyntax/ext/deriving/rand.rs b/src/libsyntax/ext/deriving/rand.rs
index c4e64d58c29..4f6e4d1fb3c 100644
--- a/src/libsyntax/ext/deriving/rand.rs
+++ b/src/libsyntax/ext/deriving/rand.rs
@@ -17,11 +17,13 @@ use ext::deriving::generic::*;
 use ext::deriving::generic::ty::*;
 use ptr::P;
 
-pub fn expand_deriving_rand(cx: &mut ExtCtxt,
-                            span: Span,
-                            mitem: &MetaItem,
-                            item: &Item,
-                            push: |P<Item>|) {
+pub fn expand_deriving_rand<F>(cx: &mut ExtCtxt,
+                               span: Span,
+                               mitem: &MetaItem,
+                               item: &Item,
+                               push: F) where
+    F: FnOnce(P<Item>),
+{
     let trait_def = TraitDef {
         span: span,
         attributes: Vec::new(),
@@ -64,7 +66,7 @@ fn rand_substructure(cx: &mut ExtCtxt, trait_span: Span, substr: &Substructure)
         cx.ident_of("Rand"),
         cx.ident_of("rand")
     );
-    let rand_call = |cx: &mut ExtCtxt, span| {
+    let mut rand_call = |&mut: cx: &mut ExtCtxt, span| {
         cx.expr_call_global(span,
                             rand_ident.clone(),
                             vec!(rng.clone()))
@@ -133,12 +135,14 @@ fn rand_substructure(cx: &mut ExtCtxt, trait_span: Span, substr: &Substructure)
         _ => cx.bug("Non-static method in `deriving(Rand)`")
     };
 
-    fn rand_thing(cx: &mut ExtCtxt,
-                  trait_span: Span,
-                  ctor_path: ast::Path,
-                  summary: &StaticFields,
-                  rand_call: |&mut ExtCtxt, Span| -> P<Expr>)
-                  -> P<Expr> {
+    fn rand_thing<F>(cx: &mut ExtCtxt,
+                     trait_span: Span,
+                     ctor_path: ast::Path,
+                     summary: &StaticFields,
+                     mut rand_call: F)
+                     -> P<Expr> where
+        F: FnMut(&mut ExtCtxt, Span) -> P<Expr>,
+    {
         let path = cx.expr_path(ctor_path.clone());
         match *summary {
             Unnamed(ref fields) => {
diff --git a/src/libsyntax/ext/deriving/show.rs b/src/libsyntax/ext/deriving/show.rs
index 322a84eaa2b..a68b521bbc9 100644
--- a/src/libsyntax/ext/deriving/show.rs
+++ b/src/libsyntax/ext/deriving/show.rs
@@ -21,11 +21,13 @@ use ptr::P;
 
 use std::collections::HashMap;
 
-pub fn expand_deriving_show(cx: &mut ExtCtxt,
-                            span: Span,
-                            mitem: &MetaItem,
-                            item: &Item,
-                            push: |P<Item>|) {
+pub fn expand_deriving_show<F>(cx: &mut ExtCtxt,
+                               span: Span,
+                               mitem: &MetaItem,
+                               item: &Item,
+                               push: F) where
+    F: FnOnce(P<Item>),
+{
     // &mut ::std::fmt::Formatter
     let fmtr = Ptr(box Literal(Path::new(vec!("std", "fmt", "Formatter"))),
                    Borrowed(None, ast::MutMutable));
diff --git a/src/libsyntax/ext/deriving/zero.rs b/src/libsyntax/ext/deriving/zero.rs
index 7f265b529ff..ea32549cad2 100644
--- a/src/libsyntax/ext/deriving/zero.rs
+++ b/src/libsyntax/ext/deriving/zero.rs
@@ -17,11 +17,13 @@ use ext::deriving::generic::ty::*;
 use parse::token::InternedString;
 use ptr::P;
 
-pub fn expand_deriving_zero(cx: &mut ExtCtxt,
-                            span: Span,
-                            mitem: &MetaItem,
-                            item: &Item,
-                            push: |P<Item>|) {
+pub fn expand_deriving_zero<F>(cx: &mut ExtCtxt,
+                               span: Span,
+                               mitem: &MetaItem,
+                               item: &Item,
+                               push: F) where
+    F: FnOnce(P<Item>),
+{
     let inline = cx.meta_word(span, InternedString::new("inline"));
     let attrs = vec!(cx.attribute(span, inline));
     let trait_def = TraitDef {
diff --git a/src/libsyntax/ext/expand.rs b/src/libsyntax/ext/expand.rs
index a697d332d16..9c4e85f16ff 100644
--- a/src/libsyntax/ext/expand.rs
+++ b/src/libsyntax/ext/expand.rs
@@ -238,11 +238,13 @@ pub fn expand_expr(e: P<ast::Expr>, fld: &mut MacroExpander) -> P<ast::Expr> {
 /// of expansion and the mark which must be applied to the result.
 /// Our current interface doesn't allow us to apply the mark to the
 /// result until after calling make_expr, make_items, etc.
-fn expand_mac_invoc<T>(mac: ast::Mac, span: codemap::Span,
-                       parse_thunk: |Box<MacResult>|->Option<T>,
-                       mark_thunk: |T,Mrk|->T,
-                       fld: &mut MacroExpander)
-                       -> Option<T>
+fn expand_mac_invoc<T, F, G>(mac: ast::Mac, span: codemap::Span,
+                             parse_thunk: F,
+                             mark_thunk: G,
+                             fld: &mut MacroExpander)
+                             -> Option<T> where
+    F: FnOnce(Box<MacResult>) -> Option<T>,
+    G: FnOnce(T, Mrk) -> T,
 {
     match mac.node {
         // it would almost certainly be cleaner to pass the whole
diff --git a/src/libsyntax/ext/mtwt.rs b/src/libsyntax/ext/mtwt.rs
index 48120b575ac..a4e06aeaf63 100644
--- a/src/libsyntax/ext/mtwt.rs
+++ b/src/libsyntax/ext/mtwt.rs
@@ -105,9 +105,11 @@ pub fn apply_renames(renames: &RenameList, ctxt: SyntaxContext) -> SyntaxContext
 }
 
 /// Fetch the SCTable from TLS, create one if it doesn't yet exist.
-pub fn with_sctable<T>(op: |&SCTable| -> T) -> T {
+pub fn with_sctable<T, F>(op: F) -> T where
+    F: FnOnce(&SCTable) -> T,
+{
     thread_local!(static SCTABLE_KEY: SCTable = new_sctable_internal())
-    SCTABLE_KEY.with(|slot| op(slot))
+    SCTABLE_KEY.with(move |slot| op(slot))
 }
 
 // Make a fresh syntax context table with EmptyCtxt in slot zero
@@ -167,12 +169,14 @@ type ResolveTable = HashMap<(Name,SyntaxContext),Name>;
 
 // okay, I admit, putting this in TLS is not so nice:
 // fetch the SCTable from TLS, create one if it doesn't yet exist.
-fn with_resolve_table_mut<T>(op: |&mut ResolveTable| -> T) -> T {
+fn with_resolve_table_mut<T, F>(op: F) -> T where
+    F: FnOnce(&mut ResolveTable) -> T,
+{
     thread_local!(static RESOLVE_TABLE_KEY: RefCell<ResolveTable> = {
         RefCell::new(HashMap::new())
     })
 
-    RESOLVE_TABLE_KEY.with(|slot| op(&mut *slot.borrow_mut()))
+    RESOLVE_TABLE_KEY.with(move |slot| op(&mut *slot.borrow_mut()))
 }
 
 /// Resolve a syntax object to a name, per MTWT.
diff --git a/src/libsyntax/fold.rs b/src/libsyntax/fold.rs
index 69e311c57f5..0318dd5b0cd 100644
--- a/src/libsyntax/fold.rs
+++ b/src/libsyntax/fold.rs
@@ -32,11 +32,11 @@ use std::rc::Rc;
 
 // This could have a better place to live.
 pub trait MoveMap<T> {
-    fn move_map(self, f: |T| -> T) -> Self;
+    fn move_map<F>(self, f: F) -> Self where F: FnMut(T) -> T;
 }
 
 impl<T> MoveMap<T> for Vec<T> {
-    fn move_map(mut self, f: |T| -> T) -> Vec<T> {
+    fn move_map<F>(mut self, mut f: F) -> Vec<T> where F: FnMut(T) -> T {
         for p in self.iter_mut() {
             unsafe {
                 // FIXME(#5016) this shouldn't need to zero to be safe.
@@ -48,7 +48,7 @@ impl<T> MoveMap<T> for Vec<T> {
 }
 
 impl<T> MoveMap<T> for OwnedSlice<T> {
-    fn move_map(self, f: |T| -> T) -> OwnedSlice<T> {
+    fn move_map<F>(self, f: F) -> OwnedSlice<T> where F: FnMut(T) -> T {
         OwnedSlice::from_vec(self.into_vec().move_map(f))
     }
 }
diff --git a/src/libsyntax/parse/lexer/mod.rs b/src/libsyntax/parse/lexer/mod.rs
index 4c15fae9feb..50c7258fe1c 100644
--- a/src/libsyntax/parse/lexer/mod.rs
+++ b/src/libsyntax/parse/lexer/mod.rs
@@ -244,7 +244,9 @@ impl<'a> StringReader<'a> {
     /// Calls `f` with a string slice of the source text spanning from `start`
     /// up to but excluding `self.last_pos`, meaning the slice does not include
     /// the character `self.curr`.
-    pub fn with_str_from<T>(&self, start: BytePos, f: |s: &str| -> T) -> T {
+    pub fn with_str_from<T, F>(&self, start: BytePos, f: F) -> T where
+        F: FnOnce(&str) -> T,
+    {
         self.with_str_from_to(start, self.last_pos, f)
     }
 
@@ -264,7 +266,9 @@ impl<'a> StringReader<'a> {
 
     /// Calls `f` with a string slice of the source text spanning from `start`
     /// up to but excluding `end`.
-    fn with_str_from_to<T>(&self, start: BytePos, end: BytePos, f: |s: &str| -> T) -> T {
+    fn with_str_from_to<T, F>(&self, start: BytePos, end: BytePos, f: F) -> T where
+        F: FnOnce(&str) -> T,
+    {
         f(self.filemap.src.slice(
                 self.byte_offset(start).to_uint(),
                 self.byte_offset(end).to_uint()))
diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs
index 92c7380a61d..8c44f9fdf26 100644
--- a/src/libsyntax/parse/parser.rs
+++ b/src/libsyntax/parse/parser.rs
@@ -718,11 +718,12 @@ impl<'a> Parser<'a> {
     }
 
     /// Parse a sequence bracketed by `|` and `|`, stopping before the `|`.
-    fn parse_seq_to_before_or<T>(
-                              &mut self,
-                              sep: &token::Token,
-                              f: |&mut Parser| -> T)
-                              -> Vec<T> {
+    fn parse_seq_to_before_or<T, F>(&mut self,
+                                    sep: &token::Token,
+                                    mut f: F)
+                                    -> Vec<T> where
+        F: FnMut(&mut Parser) -> T,
+    {
         let mut first = true;
         let mut vector = Vec::new();
         while self.token != token::BinOp(token::Or) &&
@@ -769,10 +770,12 @@ impl<'a> Parser<'a> {
         }
     }
 
-    pub fn parse_seq_to_before_gt_or_return<T>(&mut self,
-                                               sep: Option<token::Token>,
-                                               f: |&mut Parser| -> Option<T>)
-                                               -> (OwnedSlice<T>, bool) {
+    pub fn parse_seq_to_before_gt_or_return<T, F>(&mut self,
+                                                  sep: Option<token::Token>,
+                                                  mut f: F)
+                                                  -> (OwnedSlice<T>, bool) where
+        F: FnMut(&mut Parser) -> Option<T>,
+    {
         let mut v = Vec::new();
         // This loop works by alternating back and forth between parsing types
         // and commas.  For example, given a string `A, B,>`, the parser would
@@ -802,28 +805,34 @@ impl<'a> Parser<'a> {
 
     /// Parse a sequence bracketed by '<' and '>', stopping
     /// before the '>'.
-    pub fn parse_seq_to_before_gt<T>(&mut self,
-                                     sep: Option<token::Token>,
-                                     f: |&mut Parser| -> T)
-                                     -> OwnedSlice<T> {
+    pub fn parse_seq_to_before_gt<T, F>(&mut self,
+                                        sep: Option<token::Token>,
+                                        mut f: F)
+                                        -> OwnedSlice<T> where
+        F: FnMut(&mut Parser) -> T,
+    {
         let (result, returned) = self.parse_seq_to_before_gt_or_return(sep, |p| Some(f(p)));
         assert!(!returned);
         return result;
     }
 
-    pub fn parse_seq_to_gt<T>(&mut self,
-                              sep: Option<token::Token>,
-                              f: |&mut Parser| -> T)
-                              -> OwnedSlice<T> {
+    pub fn parse_seq_to_gt<T, F>(&mut self,
+                                 sep: Option<token::Token>,
+                                 f: F)
+                                 -> OwnedSlice<T> where
+        F: FnMut(&mut Parser) -> T,
+    {
         let v = self.parse_seq_to_before_gt(sep, f);
         self.expect_gt();
         return v;
     }
 
-    pub fn parse_seq_to_gt_or_return<T>(&mut self,
-                                        sep: Option<token::Token>,
-                                        f: |&mut Parser| -> Option<T>)
-                                        -> (OwnedSlice<T>, bool) {
+    pub fn parse_seq_to_gt_or_return<T, F>(&mut self,
+                                           sep: Option<token::Token>,
+                                           f: F)
+                                           -> (OwnedSlice<T>, bool) where
+        F: FnMut(&mut Parser) -> Option<T>,
+    {
         let (v, returned) = self.parse_seq_to_before_gt_or_return(sep, f);
         if !returned {
             self.expect_gt();
@@ -834,12 +843,13 @@ impl<'a> Parser<'a> {
     /// Parse a sequence, including the closing delimiter. The function
     /// f must consume tokens until reaching the next separator or
     /// closing bracket.
-    pub fn parse_seq_to_end<T>(
-                            &mut self,
-                            ket: &token::Token,
-                            sep: SeqSep,
-                            f: |&mut Parser| -> T)
-                            -> Vec<T> {
+    pub fn parse_seq_to_end<T, F>(&mut self,
+                                  ket: &token::Token,
+                                  sep: SeqSep,
+                                  f: F)
+                                  -> Vec<T> where
+        F: FnMut(&mut Parser) -> T,
+    {
         let val = self.parse_seq_to_before_end(ket, sep, f);
         self.bump();
         val
@@ -848,12 +858,13 @@ impl<'a> Parser<'a> {
     /// Parse a sequence, not including the closing delimiter. The function
     /// f must consume tokens until reaching the next separator or
     /// closing bracket.
-    pub fn parse_seq_to_before_end<T>(
-                                   &mut self,
-                                   ket: &token::Token,
-                                   sep: SeqSep,
-                                   f: |&mut Parser| -> T)
-                                   -> Vec<T> {
+    pub fn parse_seq_to_before_end<T, F>(&mut self,
+                                         ket: &token::Token,
+                                         sep: SeqSep,
+                                         mut f: F)
+                                         -> Vec<T> where
+        F: FnMut(&mut Parser) -> T,
+    {
         let mut first: bool = true;
         let mut v = vec!();
         while self.token != *ket {
@@ -873,13 +884,14 @@ impl<'a> Parser<'a> {
     /// Parse a sequence, including the closing delimiter. The function
     /// f must consume tokens until reaching the next separator or
     /// closing bracket.
-    pub fn parse_unspanned_seq<T>(
-                               &mut self,
-                               bra: &token::Token,
-                               ket: &token::Token,
-                               sep: SeqSep,
-                               f: |&mut Parser| -> T)
-                               -> Vec<T> {
+    pub fn parse_unspanned_seq<T, F>(&mut self,
+                                     bra: &token::Token,
+                                     ket: &token::Token,
+                                     sep: SeqSep,
+                                     f: F)
+                                     -> Vec<T> where
+        F: FnMut(&mut Parser) -> T,
+    {
         self.expect(bra);
         let result = self.parse_seq_to_before_end(ket, sep, f);
         self.bump();
@@ -888,13 +900,14 @@ impl<'a> Parser<'a> {
 
     /// Parse a sequence parameter of enum variant. For consistency purposes,
     /// these should not be empty.
-    pub fn parse_enum_variant_seq<T>(
-                               &mut self,
-                               bra: &token::Token,
-                               ket: &token::Token,
-                               sep: SeqSep,
-                               f: |&mut Parser| -> T)
-                               -> Vec<T> {
+    pub fn parse_enum_variant_seq<T, F>(&mut self,
+                                        bra: &token::Token,
+                                        ket: &token::Token,
+                                        sep: SeqSep,
+                                        f: F)
+                                        -> Vec<T> where
+        F: FnMut(&mut Parser) -> T,
+    {
         let result = self.parse_unspanned_seq(bra, ket, sep, f);
         if result.is_empty() {
             let last_span = self.last_span;
@@ -906,13 +919,14 @@ impl<'a> Parser<'a> {
 
     // NB: Do not use this function unless you actually plan to place the
     // spanned list in the AST.
-    pub fn parse_seq<T>(
-                     &mut self,
-                     bra: &token::Token,
-                     ket: &token::Token,
-                     sep: SeqSep,
-                     f: |&mut Parser| -> T)
-                     -> Spanned<Vec<T> > {
+    pub fn parse_seq<T, F>(&mut self,
+                           bra: &token::Token,
+                           ket: &token::Token,
+                           sep: SeqSep,
+                           f: F)
+                           -> Spanned<Vec<T>> where
+        F: FnMut(&mut Parser) -> T,
+    {
         let lo = self.span.lo;
         self.expect(bra);
         let result = self.parse_seq_to_before_end(ket, sep, f);
@@ -972,8 +986,9 @@ impl<'a> Parser<'a> {
         }
         return (4 - self.buffer_start) + self.buffer_end;
     }
-    pub fn look_ahead<R>(&mut self, distance: uint, f: |&token::Token| -> R)
-                      -> R {
+    pub fn look_ahead<R, F>(&mut self, distance: uint, f: F) -> R where
+        F: FnOnce(&token::Token) -> R,
+    {
         let dist = distance as int;
         while self.buffer_length() < dist {
             self.buffer[self.buffer_end as uint] = self.reader.real_token();
@@ -4285,8 +4300,9 @@ impl<'a> Parser<'a> {
 
     /// Parse the argument list and result type of a function
     /// that may have a self type.
-    fn parse_fn_decl_with_self(&mut self, parse_arg_fn: |&mut Parser| -> Arg)
-                               -> (ExplicitSelf, P<FnDecl>) {
+    fn parse_fn_decl_with_self<F>(&mut self, parse_arg_fn: F) -> (ExplicitSelf, P<FnDecl>) where
+        F: FnMut(&mut Parser) -> Arg,
+    {
         fn maybe_parse_borrowed_explicit_self(this: &mut Parser)
                                               -> ast::ExplicitSelf_ {
             // The following things are possible to see here:
diff --git a/src/libsyntax/print/pprust.rs b/src/libsyntax/print/pprust.rs
index 26373d00aaf..6d8b8dcb8ba 100644
--- a/src/libsyntax/print/pprust.rs
+++ b/src/libsyntax/print/pprust.rs
@@ -165,7 +165,9 @@ impl<'a> State<'a> {
     }
 }
 
-pub fn to_string(f: |&mut State| -> IoResult<()>) -> String {
+pub fn to_string<F>(f: F) -> String where
+    F: FnOnce(&mut State) -> IoResult<()>,
+{
     use std::raw::TraitObject;
     let mut s = rust_printer(box Vec::new());
     f(&mut s).unwrap();
@@ -426,8 +428,10 @@ pub mod with_hygiene {
 
     // This function is the trick that all the rest of the routines
     // hang on.
-    pub fn to_string_hyg(f: |&mut super::State| -> IoResult<()>) -> String {
-        super::to_string(|s| {
+    pub fn to_string_hyg<F>(f: F) -> String where
+        F: FnOnce(&mut super::State) -> IoResult<()>,
+    {
+        super::to_string(move |s| {
             s.encode_idents_with_hygiene = true;
             f(s)
         })
@@ -580,9 +584,9 @@ impl<'a> State<'a> {
         word(&mut self.s, "*/")
     }
 
-    pub fn commasep<T>(&mut self, b: Breaks, elts: &[T],
-                       op: |&mut State, &T| -> IoResult<()>)
-        -> IoResult<()> {
+    pub fn commasep<T, F>(&mut self, b: Breaks, elts: &[T], mut op: F) -> IoResult<()> where
+        F: FnMut(&mut State, &T) -> IoResult<()>,
+    {
         try!(self.rbox(0u, b));
         let mut first = true;
         for elt in elts.iter() {
@@ -593,12 +597,14 @@ impl<'a> State<'a> {
     }
 
 
-    pub fn commasep_cmnt<T>(
-                         &mut self,
-                         b: Breaks,
-                         elts: &[T],
-                         op: |&mut State, &T| -> IoResult<()>,
-                         get_span: |&T| -> codemap::Span) -> IoResult<()> {
+    pub fn commasep_cmnt<T, F, G>(&mut self,
+                                  b: Breaks,
+                                  elts: &[T],
+                                  mut op: F,
+                                  mut get_span: G) -> IoResult<()> where
+        F: FnMut(&mut State, &T) -> IoResult<()>,
+        G: FnMut(&T) -> codemap::Span,
+    {
         try!(self.rbox(0u, b));
         let len = elts.len();
         let mut i = 0u;
diff --git a/src/libsyntax/ptr.rs b/src/libsyntax/ptr.rs
index 1b231ed861b..1b3ebde2461 100644
--- a/src/libsyntax/ptr.rs
+++ b/src/libsyntax/ptr.rs
@@ -56,12 +56,16 @@ pub fn P<T: 'static>(value: T) -> P<T> {
 impl<T: 'static> P<T> {
     /// Move out of the pointer.
     /// Intended for chaining transformations not covered by `map`.
-    pub fn and_then<U>(self, f: |T| -> U) -> U {
+    pub fn and_then<U, F>(self, f: F) -> U where
+        F: FnOnce(T) -> U,
+    {
         f(*self.ptr)
     }
 
     /// Transform the inner value, consuming `self` and producing a new `P<T>`.
-    pub fn map(mut self, f: |T| -> T) -> P<T> {
+    pub fn map<F>(mut self, f: F) -> P<T> where
+        F: FnOnce(T) -> T,
+    {
         unsafe {
             let p = &mut *self.ptr;
             // FIXME(#5016) this shouldn't need to zero to be safe.
diff --git a/src/libsyntax/util/parser_testing.rs b/src/libsyntax/util/parser_testing.rs
index c1ea8f60b82..83bbff8473d 100644
--- a/src/libsyntax/util/parser_testing.rs
+++ b/src/libsyntax/util/parser_testing.rs
@@ -31,7 +31,9 @@ pub fn string_to_parser<'a>(ps: &'a ParseSess, source_str: String) -> Parser<'a>
                                source_str)
 }
 
-fn with_error_checking_parse<T>(s: String, f: |&mut Parser| -> T) -> T {
+fn with_error_checking_parse<T, F>(s: String, f: F) -> T where
+    F: FnOnce(&mut Parser) -> T,
+{
     let ps = new_parse_sess();
     let mut p = string_to_parser(&ps, s);
     let x = f(&mut p);
diff --git a/src/libsyntax/util/small_vector.rs b/src/libsyntax/util/small_vector.rs
index d56e4f70449..8d050e34abf 100644
--- a/src/libsyntax/util/small_vector.rs
+++ b/src/libsyntax/util/small_vector.rs
@@ -171,7 +171,7 @@ impl<T> Iterator<T> for MoveItems<T> {
 }
 
 impl<T> MoveMap<T> for SmallVector<T> {
-    fn move_map(self, f: |T| -> T) -> SmallVector<T> {
+    fn move_map<F>(self, mut f: F) -> SmallVector<T> where F: FnMut(T) -> T {
         let repr = match self.repr {
             Zero => Zero,
             One(v) => One(f(v)),