Make it illegal to use modes in a fn signature with providing

an explicit variable name. (Step one to changing the defaults)

First step to #3535

src/libcore/at_vec.rs

@@ -50,7 +50,8 @@ pure fn capacity<T>(&&v: @[const T]) -> uint {
  *             onto the vector being constructed.
  */
 #[inline(always)]
-pure fn build_sized<A>(size: uint, builder: fn(push: pure fn(+A))) -> @[A] {
+pure fn build_sized<A>(size: uint,
+                       builder: fn(push: pure fn(+v: A))) -> @[A] {
     let mut vec = @[];
     unsafe { raw::reserve(vec, size); }
     builder(|+x| unsafe { raw::push(vec, move x) });
@@ -68,7 +69,7 @@ pure fn build_sized<A>(size: uint, builder: fn(push: pure fn(+A))) -> @[A] {
  *             onto the vector being constructed.
  */
 #[inline(always)]
-pure fn build<A>(builder: fn(push: pure fn(+A))) -> @[A] {
+pure fn build<A>(builder: fn(push: pure fn(+v: A))) -> @[A] {
     build_sized(4, builder)
 }
 
@@ -86,7 +87,7 @@ pure fn build<A>(builder: fn(push: pure fn(+A))) -> @[A] {
  */
 #[inline(always)]
 pure fn build_sized_opt<A>(size: Option<uint>,
-                           builder: fn(push: pure fn(+A))) -> @[A] {
+                           builder: fn(push: pure fn(+v: A))) -> @[A] {
     build_sized(size.get_default(4), builder)
 }
 

src/libcore/dvec.rs

@@ -93,7 +93,7 @@ priv impl<A> DVec<A> {
     }
 
     #[inline(always)]
-    fn check_out<B>(f: fn(-~[A]) -> B) -> B {
+    fn check_out<B>(f: fn(-v: ~[A]) -> B) -> B {
         unsafe {
             let mut data = cast::reinterpret_cast(&null::<()>());
             data <-> self.data;
@@ -126,7 +126,7 @@ impl<A> DVec<A> {
      * and return a new vector to replace it with.
      */
     #[inline(always)]
-    fn swap(f: fn(-~[A]) -> ~[A]) {
+    fn swap(f: fn(-v: ~[A]) -> ~[A]) {
         self.check_out(|v| self.give_back(f(move v)))
     }
 
@@ -136,7 +136,7 @@ impl<A> DVec<A> {
      * and return a new vector to replace it with.
      */
     #[inline(always)]
-    fn swap_mut(f: fn(-~[mut A]) -> ~[mut A]) {
+    fn swap_mut(f: fn(-v: ~[mut A]) -> ~[mut A]) {
         do self.swap |v| {
             vec::from_mut(f(vec::to_mut(move v)))
         }

src/libcore/io.rs

@@ -827,7 +827,7 @@ mod fsync {
     // FIXME (#2004) find better way to create resources within lifetime of
     // outer res
     fn FILE_res_sync(&&file: FILERes, opt_level: Option<Level>,
-                  blk: fn(&&Res<*libc::FILE>)) {
+                  blk: fn(&&v: Res<*libc::FILE>)) {
         blk(Res({
             val: file.f, opt_level: opt_level,
             fsync_fn: fn@(&&file: *libc::FILE, l: Level) -> int {
@@ -838,7 +838,7 @@ mod fsync {
 
     // fsync fd after executing blk
     fn fd_res_sync(&&fd: FdRes, opt_level: Option<Level>,
-                   blk: fn(&&Res<fd_t>)) {
+                   blk: fn(&&v: Res<fd_t>)) {
         blk(Res({
             val: fd.fd, opt_level: opt_level,
             fsync_fn: fn@(&&fd: fd_t, l: Level) -> int {
@@ -852,7 +852,7 @@ mod fsync {
 
     // Call o.fsync after executing blk
     fn obj_sync(&&o: FSyncable, opt_level: Option<Level>,
-                blk: fn(&&Res<FSyncable>)) {
+                blk: fn(&&v: Res<FSyncable>)) {
         blk(Res({
             val: o, opt_level: opt_level,
             fsync_fn: fn@(&&o: FSyncable, l: Level) -> int {

src/libcore/iter.rs

@@ -63,7 +63,7 @@ trait Buildable<A> {
      *             onto the sequence being constructed.
      */
      static pure fn build_sized(size: uint,
-                                builder: fn(push: pure fn(+A))) -> self;
+                                builder: fn(push: pure fn(+v: A))) -> self;
 }
 
 pure fn eachi<A,IA:BaseIter<A>>(self: IA, blk: fn(uint, v: &A) -> bool) {
@@ -223,7 +223,7 @@ pure fn find<A: Copy,IA:BaseIter<A>>(self: IA,
  *             onto the sequence being constructed.
  */
 #[inline(always)]
-pure fn build<A,B: Buildable<A>>(builder: fn(push: pure fn(+A))) -> B {
+pure fn build<A,B: Buildable<A>>(builder: fn(push: pure fn(+v: A))) -> B {
     build_sized(4, builder)
 }
 
@@ -243,7 +243,7 @@ pure fn build<A,B: Buildable<A>>(builder: fn(push: pure fn(+A))) -> B {
 #[inline(always)]
 pure fn build_sized_opt<A,B: Buildable<A>>(
     size: Option<uint>,
-    builder: fn(push: pure fn(+A))) -> B {
+    builder: fn(push: pure fn(+v: A))) -> B {
 
     build_sized(size.get_default(4), builder)
 }

src/libcore/option.rs

@@ -69,7 +69,7 @@ pure fn map_ref<T, U>(opt: &Option<T>, f: fn(x: &T) -> U) -> Option<U> {
     match *opt { Some(ref x) => Some(f(x)), None => None }
 }
 
-pure fn map_consume<T, U>(+opt: Option<T>, f: fn(+T) -> U) -> Option<U> {
+pure fn map_consume<T, U>(+opt: Option<T>, f: fn(+v: T) -> U) -> Option<U> {
     /*!
      * As `map`, but consumes the option and gives `f` ownership to avoid
      * copying.
@@ -107,7 +107,7 @@ pure fn or<T>(+opta: Option<T>, +optb: Option<T>) -> Option<T> {
 }
 
 #[inline(always)]
-pure fn while_some<T>(+x: Option<T>, blk: fn(+T) -> Option<T>) {
+pure fn while_some<T>(+x: Option<T>, blk: fn(+v: T) -> Option<T>) {
     //! Applies a function zero or more times until the result is none.
 
     let mut opt <- x;
@@ -248,7 +248,7 @@ impl<T: Copy> Option<T> {
      */
     pure fn expect(reason: ~str) -> T { expect(self, reason) }
     /// Applies a function zero or more times until the result is none.
-    pure fn while_some(blk: fn(+T) -> Option<T>) { while_some(self, blk) }
+    pure fn while_some(blk: fn(+v: T) -> Option<T>) { while_some(self, blk) }
 }
 
 #[cfg(stage0)]

src/libcore/pipes.rs

@@ -889,7 +889,7 @@ endpoint is passed to the new task.
 fn spawn_service<T: Send, Tb: Send>(
     init: extern fn() -> (SendPacketBuffered<T, Tb>,
                           RecvPacketBuffered<T, Tb>),
-    +service: fn~(+RecvPacketBuffered<T, Tb>))
+    +service: fn~(+v: RecvPacketBuffered<T, Tb>))
     -> SendPacketBuffered<T, Tb>
 {
     let (client, server) = init();
@@ -913,7 +913,7 @@ receive state.
 fn spawn_service_recv<T: Send, Tb: Send>(
     init: extern fn() -> (RecvPacketBuffered<T, Tb>,
                           SendPacketBuffered<T, Tb>),
-    +service: fn~(+SendPacketBuffered<T, Tb>))
+    +service: fn~(+v: SendPacketBuffered<T, Tb>))
     -> RecvPacketBuffered<T, Tb>
 {
     let (client, server) = init();

src/libcore/str.rs

@@ -2109,7 +2109,8 @@ mod raw {
     unsafe fn from_byte(u: u8) -> ~str { raw::from_bytes([u]) }
 
     /// Form a slice from a *u8 buffer of the given length without copying.
-    unsafe fn buf_as_slice<T>(buf: *u8, len: uint, f: fn(&& &str) -> T) -> T {
+    unsafe fn buf_as_slice<T>(buf: *u8, len: uint,
+                              f: fn(&&v: &str) -> T) -> T {
         let v = (buf, len + 1);
         assert is_utf8(::cast::reinterpret_cast(&v));
         f(::cast::transmute(move v))

src/libcore/task.rs

@@ -338,7 +338,7 @@ type TaskOpts = {
 // FIXME (#2585): Replace the 'consumed' bit with move mode on self
 enum TaskBuilder = {
     opts: TaskOpts,
-    gen_body: fn@(+fn~()) -> fn~(),
+    gen_body: fn@(+v: fn~()) -> fn~(),
     can_not_copy: Option<util::NonCopyable>,
     mut consumed: bool,
 };
@@ -466,7 +466,7 @@ impl TaskBuilder {
      * # Failure
      * Fails if a future_result was already set for this task.
      */
-    fn future_result(blk: fn(+future::Future<TaskResult>)) -> TaskBuilder {
+    fn future_result(blk: fn(+v: future::Future<TaskResult>)) -> TaskBuilder {
         // FIXME (#1087, #1857): Once linked failure and notification are
         // handled in the library, I can imagine implementing this by just
         // registering an arbitrary number of task::on_exit handlers and
@@ -528,7 +528,7 @@ impl TaskBuilder {
      * generator by applying the task body which results from the
      * existing body generator to the new body generator.
      */
-    fn add_wrapper(wrapper: fn@(+fn~()) -> fn~()) -> TaskBuilder {
+    fn add_wrapper(wrapper: fn@(+v: fn~()) -> fn~()) -> TaskBuilder {
         let prev_gen_body = self.gen_body;
         let notify_chan = if self.opts.notify_chan.is_none() {
             None
@@ -578,7 +578,7 @@ impl TaskBuilder {
         spawn::spawn_raw(move opts, x.gen_body(move f));
     }
     /// Runs a task, while transfering ownership of one argument to the child.
-    fn spawn_with<A: Send>(+arg: A, +f: fn~(+A)) {
+    fn spawn_with<A: Send>(+arg: A, +f: fn~(+v: A)) {
         let arg = ~mut Some(move arg);
         do self.spawn |move arg, move f|{
             f(option::swap_unwrap(arg))
@@ -705,7 +705,7 @@ fn spawn_supervised(+f: fn~()) {
     task().supervised().spawn(move f)
 }
 
-fn spawn_with<A:Send>(+arg: A, +f: fn~(+A)) {
+fn spawn_with<A:Send>(+arg: A, +f: fn~(+v: A)) {
     /*!
      * Runs a task, while transfering ownership of one argument to the
      * child.
@@ -1246,7 +1246,7 @@ fn test_spawn_sched_blocking() {
 }
 
 #[cfg(test)]
-fn avoid_copying_the_body(spawnfn: fn(+fn~())) {
+fn avoid_copying_the_body(spawnfn: fn(+v: fn~())) {
     let p = comm::Port::<uint>();
     let ch = comm::Chan(p);
 

src/libcore/task/local_data.rs

@@ -43,7 +43,7 @@ use local_data_priv::{
  *
  * These two cases aside, the interface is safe.
  */
-type LocalDataKey<T: Owned> = &fn(+@T);
+type LocalDataKey<T: Owned> = &fn(+v: @T);
 
 /**
  * Remove a task-local data value from the table, returning the

src/libcore/task/spawn.rs

@@ -82,7 +82,7 @@ fn taskset_remove(tasks: &mut TaskSet, task: *rust_task) {
     let was_present = tasks.remove(&task);
     assert was_present;
 }
-fn taskset_each(tasks: &TaskSet, blk: fn(+*rust_task) -> bool) {
+fn taskset_each(tasks: &TaskSet, blk: fn(+v: *rust_task) -> bool) {
     tasks.each_key(|k| blk(*k))
 }
 

src/libcore/vec.rs

@@ -235,7 +235,8 @@ pure fn with_capacity<T>(capacity: uint) -> ~[T] {
  *             onto the vector being constructed.
  */
 #[inline(always)]
-pure fn build_sized<A>(size: uint, builder: fn(push: pure fn(+A))) -> ~[A] {
+pure fn build_sized<A>(size: uint,
+                       builder: fn(push: pure fn(+v: A))) -> ~[A] {
     let mut vec = with_capacity(size);
     builder(|+x| unsafe { push(vec, move x) });
     move vec
@@ -252,7 +253,7 @@ pure fn build_sized<A>(size: uint, builder: fn(push: pure fn(+A))) -> ~[A] {
  *             onto the vector being constructed.
  */
 #[inline(always)]
-pure fn build<A>(builder: fn(push: pure fn(+A))) -> ~[A] {
+pure fn build<A>(builder: fn(push: pure fn(+v: A))) -> ~[A] {
     build_sized(4, builder)
 }
 
@@ -270,7 +271,7 @@ pure fn build<A>(builder: fn(push: pure fn(+A))) -> ~[A] {
  */
 #[inline(always)]
 pure fn build_sized_opt<A>(size: Option<uint>,
-                           builder: fn(push: pure fn(+A))) -> ~[A] {
+                           builder: fn(push: pure fn(+v: A))) -> ~[A] {
     build_sized(size.get_default(4), builder)
 }
 
@@ -506,7 +507,7 @@ fn unshift<T>(&v: ~[T], +x: T) {
     }
 }
 
-fn consume<T>(+v: ~[T], f: fn(uint, +T)) unsafe {
+fn consume<T>(+v: ~[T], f: fn(uint, +v: T)) unsafe {
     do as_imm_buf(v) |p, ln| {
         for uint::range(0, ln) |i| {
             let x <- *ptr::offset(p, i);
@@ -517,7 +518,7 @@ fn consume<T>(+v: ~[T], f: fn(uint, +T)) unsafe {
     raw::set_len(v, 0);
 }
 
-fn consume_mut<T>(+v: ~[mut T], f: fn(uint, +T)) unsafe {
+fn consume_mut<T>(+v: ~[mut T], f: fn(uint, +v: T)) unsafe {
     do as_imm_buf(v) |p, ln| {
         for uint::range(0, ln) |i| {
             let x <- *ptr::offset(p, i);
@@ -748,7 +749,7 @@ pure fn map<T, U>(v: &[T], f: fn(v: &T) -> U) -> ~[U] {
     move result
 }
 
-fn map_consume<T, U>(+v: ~[T], f: fn(+T) -> U) -> ~[U] {
+fn map_consume<T, U>(+v: ~[T], f: fn(+v: T) -> U) -> ~[U] {
     let mut result = ~[];
     do consume(move v) |_i, x| {
         vec::push(result, f(move x));
@@ -1808,7 +1809,7 @@ mod raw {
      * not bytes).
      */
     #[inline(always)]
-    unsafe fn form_slice<T,U>(p: *T, len: uint, f: fn(&& &[T]) -> U) -> U {
+    unsafe fn form_slice<T,U>(p: *T, len: uint, f: fn(&&v: &[T]) -> U) -> U {
         let pair = (p, len * sys::size_of::<T>());
         let v : *(&blk/[T]) =
             ::cast::reinterpret_cast(&ptr::addr_of(pair));

src/libstd/arc.rs

@@ -340,7 +340,7 @@ impl<T: Const Send> &RWARC<T> {
      * }
      * ~~~
      */
-    fn write_downgrade<U>(blk: fn(+RWWriteMode<T>) -> U) -> U {
+    fn write_downgrade<U>(blk: fn(+v: RWWriteMode<T>) -> U) -> U {
         let state = unsafe { get_shared_mutable_state(&self.x) };
         do borrow_rwlock(state).write_downgrade |write_mode| {
             check_poison(false, state.failed);

src/libstd/bitv.rs

@@ -140,7 +140,7 @@ impl BigBitv {
     }
 
     #[inline(always)]
-     fn each_storage(op: fn(&uint) -> bool) {
+     fn each_storage(op: fn(&v: uint) -> bool) {
         for uint::range(0, self.storage.len()) |i| {
             let mut w = self.storage[i];
             let b = !op(w);

src/libstd/map.rs

@@ -33,7 +33,7 @@ trait Map<K:Eq IterBytes Hash Copy, V: Copy> {
      *
      * Returns true if the key did not already exist in the map
      */
-    fn insert(+K, +V) -> bool;
+    fn insert(+v: K, +v: V) -> bool;
 
     /// Returns true if the map contains a value for the specified key
     fn contains_key(+key: K) -> bool;

src/libstd/sync.rs

@@ -539,7 +539,7 @@ impl &RWlock {
      * }
      * ~~~
      */
-    fn write_downgrade<U>(blk: fn(+RWlockWriteMode) -> U) -> U {
+    fn write_downgrade<U>(blk: fn(+v: RWlockWriteMode) -> U) -> U {
         // Implementation slightly different from the slicker 'write's above.
         // The exit path is conditional on whether the caller downgrades.
         let mut _release = None;

src/libsyntax/ast.rs

@@ -34,7 +34,7 @@ type spanned<T> = {node: T, span: span};
 /* can't import macros yet, so this is copied from token.rs. See its comment
  * there. */
 macro_rules! interner_key (
-    () => (cast::transmute::<(uint, uint), &fn(+@@token::ident_interner)>(
+    () => (cast::transmute::<(uint, uint), &fn(+v: @@token::ident_interner)>(
         (-3 as uint, 0u)))
 )
 

src/libsyntax/ext/auto_serialize.rs

@@ -351,8 +351,8 @@ fn ser_variant(cx: ext_ctxt,
                span: span,
                -s: @ast::expr,
                pfn: fn(~[@ast::pat]) -> ast::pat_,
-               bodyfn: fn(-@ast::expr, ast::blk) -> @ast::expr,
+               bodyfn: fn(-v: @ast::expr, ast::blk) -> @ast::expr,
-               argfn: fn(-@ast::expr, uint, ast::blk) -> @ast::expr)
+               argfn: fn(-v: @ast::expr, uint, ast::blk) -> @ast::expr)
     -> ast::arm {
     let vnames = do vec::from_fn(vec::len(tys)) |i| {
         cx.parse_sess().interner.intern(@fmt!("__v%u", i))
@@ -535,7 +535,7 @@ fn ser_ty(cx: ext_ctxt, tps: ser_tps_map,
 fn mk_ser_fn(cx: ext_ctxt, span: span, name: ast::ident,
              tps: ~[ast::ty_param],
              f: fn(ext_ctxt, ser_tps_map,
-                   -@ast::expr, -@ast::expr) -> ~[@ast::stmt])
+                   -v: @ast::expr, -v: @ast::expr) -> ~[@ast::stmt])
     -> @ast::item {
     let ext_cx = cx; // required for #ast
 
@@ -747,7 +747,7 @@ fn deser_ty(cx: ext_ctxt, tps: deser_tps_map,
 
 fn mk_deser_fn(cx: ext_ctxt, span: span,
                name: ast::ident, tps: ~[ast::ty_param],
-               f: fn(ext_ctxt, deser_tps_map, -@ast::expr) -> @ast::expr)
+               f: fn(ext_ctxt, deser_tps_map, -v: @ast::expr) -> @ast::expr)
     -> @ast::item {
     let ext_cx = cx; // required for #ast
 

src/libsyntax/ext/expand.rs

@@ -167,7 +167,7 @@ fn expand_mod_items(exts: HashMap<~str, syntax_extension>, cx: ext_ctxt,
 // When we enter a module, record it, for the sake of `module!`
 fn expand_item(exts: HashMap<~str, syntax_extension>,
                cx: ext_ctxt, &&it: @ast::item, fld: ast_fold,
-               orig: fn@(&&@ast::item, ast_fold) -> Option<@ast::item>)
+               orig: fn@(&&v: @ast::item, ast_fold) -> Option<@ast::item>)
     -> Option<@ast::item>
 {
     let is_mod = match it.node {

src/libsyntax/ext/pipes/ast_builder.rs

@@ -77,9 +77,9 @@ trait ext_ctxt_ast_builder {
     fn item_ty(name: ident, span: span, ty: @ast::ty) -> @ast::item;
     fn ty_vars(+ty_params: ~[ast::ty_param]) -> ~[@ast::ty];
     fn ty_field_imm(name: ident, ty: @ast::ty) -> ast::ty_field;
-    fn ty_rec(+~[ast::ty_field]) -> @ast::ty;
+    fn ty_rec(+v: ~[ast::ty_field]) -> @ast::ty;
     fn field_imm(name: ident, e: @ast::expr) -> ast::field;
-    fn rec(+~[ast::field]) -> @ast::expr;
+    fn rec(+v: ~[ast::field]) -> @ast::expr;
     fn block(+stmts: ~[@ast::stmt], e: @ast::expr) -> ast::blk;
     fn stmt_let(ident: ident, e: @ast::expr) -> @ast::stmt;
     fn stmt_expr(e: @ast::expr) -> @ast::stmt;

src/libsyntax/fold.rs

@@ -20,27 +20,27 @@ export extensions;
 
 trait ast_fold {
     fn fold_crate(crate) -> crate;
-    fn fold_crate_directive(&&@crate_directive) -> @crate_directive;
+    fn fold_crate_directive(&&v: @crate_directive) -> @crate_directive;
-    fn fold_view_item(&&@view_item) -> @view_item;
+    fn fold_view_item(&&v: @view_item) -> @view_item;
-    fn fold_foreign_item(&&@foreign_item) -> @foreign_item;
+    fn fold_foreign_item(&&v: @foreign_item) -> @foreign_item;
-    fn fold_item(&&@item) -> Option<@item>;
+    fn fold_item(&&v: @item) -> Option<@item>;
-    fn fold_struct_field(&&@struct_field) -> @struct_field;
+    fn fold_struct_field(&&v: @struct_field) -> @struct_field;
     fn fold_item_underscore(item_) -> item_;
-    fn fold_method(&&@method) -> @method;
+    fn fold_method(&&v: @method) -> @method;
     fn fold_block(blk) -> blk;
-    fn fold_stmt(&&@stmt) -> @stmt;
+    fn fold_stmt(&&v: @stmt) -> @stmt;
     fn fold_arm(arm) -> arm;
-    fn fold_pat(&&@pat) -> @pat;
+    fn fold_pat(&&v: @pat) -> @pat;
-    fn fold_decl(&&@decl) -> @decl;
+    fn fold_decl(&&v: @decl) -> @decl;
-    fn fold_expr(&&@expr) -> @expr;
+    fn fold_expr(&&v: @expr) -> @expr;
-    fn fold_ty(&&@ty) -> @ty;
+    fn fold_ty(&&v: @ty) -> @ty;
     fn fold_mod(_mod) -> _mod;
     fn fold_foreign_mod(foreign_mod) -> foreign_mod;
     fn fold_variant(variant) -> variant;
-    fn fold_ident(&&ident) -> ident;
+    fn fold_ident(&&v: ident) -> ident;
-    fn fold_path(&&@path) -> @path;
+    fn fold_path(&&v: @path) -> @path;
-    fn fold_local(&&@local) -> @local;
+    fn fold_local(&&v: @local) -> @local;
-    fn map_exprs(fn@(&&@expr) -> @expr, ~[@expr]) -> ~[@expr];
+    fn map_exprs(fn@(&&v: @expr) -> @expr, ~[@expr]) -> ~[@expr];
     fn new_id(node_id) -> node_id;
     fn new_span(span) -> span;
 }
@@ -53,11 +53,11 @@ type ast_fold_precursor = @{
     fold_crate_directive: fn@(crate_directive_, span,
                               ast_fold) -> (crate_directive_, span),
     fold_view_item: fn@(view_item_, ast_fold) -> view_item_,
-    fold_foreign_item: fn@(&&@foreign_item, ast_fold) -> @foreign_item,
+    fold_foreign_item: fn@(&&v: @foreign_item, ast_fold) -> @foreign_item,
-    fold_item: fn@(&&@item, ast_fold) -> Option<@item>,
+    fold_item: fn@(&&v: @item, ast_fold) -> Option<@item>,
-    fold_struct_field: fn@(&&@struct_field, ast_fold) -> @struct_field,
+    fold_struct_field: fn@(&&v: @struct_field, ast_fold) -> @struct_field,
     fold_item_underscore: fn@(item_, ast_fold) -> item_,
-    fold_method: fn@(&&@method, ast_fold) -> @method,
+    fold_method: fn@(&&v: @method, ast_fold) -> @method,
     fold_block: fn@(blk_, span, ast_fold) -> (blk_, span),
     fold_stmt: fn@(stmt_, span, ast_fold) -> (stmt_, span),
     fold_arm: fn@(arm, ast_fold) -> arm,
@@ -68,10 +68,10 @@ type ast_fold_precursor = @{
     fold_mod: fn@(_mod, ast_fold) -> _mod,
     fold_foreign_mod: fn@(foreign_mod, ast_fold) -> foreign_mod,
     fold_variant: fn@(variant_, span, ast_fold) -> (variant_, span),
-    fold_ident: fn@(&&ident, ast_fold) -> ident,
+    fold_ident: fn@(&&v: ident, ast_fold) -> ident,
     fold_path: fn@(path, ast_fold) -> path,
     fold_local: fn@(local_, span, ast_fold) -> (local_, span),
-    map_exprs: fn@(fn@(&&@expr) -> @expr, ~[@expr]) -> ~[@expr],
+    map_exprs: fn@(fn@(&&v: @expr) -> @expr, ~[@expr]) -> ~[@expr],
     new_id: fn@(node_id) -> node_id,
     new_span: fn@(span) -> span};
 
@@ -643,7 +643,7 @@ fn noop_fold_local(l: local_, fld: ast_fold) -> local_ {
 
 /* temporarily eta-expand because of a compiler bug with using `fn<T>` as a
    value */
-fn noop_map_exprs(f: fn@(&&@expr) -> @expr, es: ~[@expr]) -> ~[@expr] {
+fn noop_map_exprs(f: fn@(&&v: @expr) -> @expr, es: ~[@expr]) -> ~[@expr] {
     return vec::map(es, |x| f(*x));
 }
 
@@ -773,7 +773,7 @@ impl ast_fold_precursor: ast_fold {
         let (n, s) = self.fold_local(x.node, x.span, self as ast_fold);
         return @{node: n, span: self.new_span(s)};
     }
-    fn map_exprs(f: fn@(&&@expr) -> @expr, e: ~[@expr]) -> ~[@expr] {
+    fn map_exprs(f: fn@(&&v: @expr) -> @expr, e: ~[@expr]) -> ~[@expr] {
         self.map_exprs(f, e)
     }
     fn new_id(node_id: ast::node_id) -> node_id {

src/libsyntax/parse/obsolete.rs

@@ -21,7 +21,8 @@ pub enum ObsoleteSyntax {
     ObsoleteWith,
     ObsoleteClassMethod,
     ObsoleteClassTraits,
-    ObsoletePrivSection
+    ObsoletePrivSection,
+    ObsoleteModeInFnType
 }
 
 #[cfg(stage0)]
@@ -99,6 +100,11 @@ impl parser : ObsoleteReporter {
                 "the `priv` keyword is applied to individual items, methods, \
                  and fields"
             ),
+            ObsoleteModeInFnType => (
+                "mode without identifier in fn type",
+                "to use a (deprecated) mode in a fn type, you should \
+                 give the argument an explicit name (like `&&v: int`)"
+            ),
         };
 
         self.report(sp, kind, kind_str, desc);

src/libsyntax/parse/parser.rs

@@ -19,7 +19,8 @@ use obsolete::{
     ObsoleteReporter, ObsoleteSyntax,
     ObsoleteLowerCaseKindBounds, ObsoleteLet,
     ObsoleteFieldTerminator, ObsoleteStructCtor,
-    ObsoleteWith, ObsoleteClassMethod, ObsoleteClassTraits
+    ObsoleteWith, ObsoleteClassMethod, ObsoleteClassTraits,
+    ObsoleteModeInFnType
 };
 use ast::{_mod, add, alt_check, alt_exhaustive, arg, arm, attribute,
              bind_by_ref, bind_by_implicit_ref, bind_by_value, bind_by_move,
@@ -618,6 +619,15 @@ impl parser {
             } else { special_idents::invalid }
         };
 
+        match m {
+            expl(_) => {
+                if i == special_idents::invalid {
+                    self.obsolete(copy self.span, ObsoleteModeInFnType);
+                }
+            }
+            _ => {}
+        }
+
         let t = self.parse_ty(false);
 
         {mode: m, ty: t, ident: i, id: self.get_id()}
@@ -1585,7 +1595,7 @@ impl parser {
     }
 
     fn parse_sugary_call_expr(keyword: ~str,
-                              ctor: fn(+@expr) -> expr_) -> @expr {
+                              ctor: fn(+v: @expr) -> expr_) -> @expr {
         let lo = self.last_span;
         // Parse the callee `foo` in
         //    for foo || {
@@ -2400,7 +2410,7 @@ impl parser {
                                     fn(parser) -> arg_or_capture_item)
                             -> (self_ty, fn_decl, capture_clause) {
 
-        fn maybe_parse_self_ty(cnstr: fn(+mutability) -> ast::self_ty_,
+        fn maybe_parse_self_ty(cnstr: fn(+v: mutability) -> ast::self_ty_,
                                p: parser) -> ast::self_ty_ {
             // We need to make sure it isn't a mode or a type
             if p.token_is_keyword(~"self", p.look_ahead(1)) ||

src/test/bench/pingpong.rs

@@ -65,7 +65,7 @@ macro_rules! follow (
 )
 
 fn switch<T: Send, Tb: Send, U>(+endp: pipes::RecvPacketBuffered<T, Tb>,
-                      f: fn(+Option<T>) -> U) -> U {
+                      f: fn(+v: Option<T>) -> U) -> U {
     f(pipes::try_recv(endp))
 }
 

src/test/bench/task-perf-word-count-generic.rs

@@ -80,7 +80,7 @@ fn reduce(&&word: ~str, get: map_reduce::getter<int>) {
     let mut count = 0;
 
     loop { match get() { Some(_) => { count += 1; } None => { break; } } }
-    
+
     io::println(fmt!("%s\t%?", word, count));
 }
 
@@ -89,7 +89,7 @@ struct box<T> {
 }
 
 impl<T> box<T> {
-    fn swap(f: fn(+T) -> T) {
+    fn swap(f: fn(+v: T) -> T) {
         let mut tmp = None;
         self.contents <-> tmp;
         self.contents = Some(f(option::unwrap(tmp)));

src/test/compile-fail/arg-style-mismatch.rs

@@ -1,5 +1,5 @@
 // error-pattern: mismatched types
 
 fn f(&&_x: int) {}
-fn g(_a: fn(+int)) {}
+fn g(_a: fn(+v: int)) {}
 fn main() { g(f); }

src/test/compile-fail/issue-2766-a.rs

@@ -4,7 +4,7 @@ mod stream {
     mod server {
         #[legacy_exports];
         impl<T: Send> stream<T> {
-            fn recv() -> extern fn(+stream<T>) -> stream::stream<T> {
+            fn recv() -> extern fn(+v: stream<T>) -> stream::stream<T> {
               // resolve really should report just one error here.
               // Change the test case when it changes.
               fn recv(+pipe: stream<T>) -> stream::stream<T> { //~ ERROR attempt to use a type argument out of scope

src/test/run-pass/class-impl-very-parameterized-trait.rs

@@ -70,7 +70,7 @@ impl<T: Copy> cat<T> : Map<int, T> {
     }
   }
 
-  pure fn each(f: fn(+int, +T) -> bool) {
+  pure fn each(f: fn(+v: int, +v: T) -> bool) {
     let mut n = int::abs(self.meows);
     while n > 0 {
         if !f(n, self.name) { break; }
@@ -78,10 +78,10 @@ impl<T: Copy> cat<T> : Map<int, T> {
     }
   }
 
-  pure fn each_key(&&f: fn(+int) -> bool) {
+  pure fn each_key(&&f: fn(+v: int) -> bool) {
     for self.each |k, _v| { if !f(k) { break; } loop;};
   }
-  pure fn each_value(&&f: fn(+T) -> bool) {
+  pure fn each_value(&&f: fn(+v: T) -> bool) {
     for self.each |_k, v| { if !f(v) { break; } loop;};
   }
 

src/test/run-pass/fixed-point-bind-box.rs

@@ -9,7 +9,7 @@ fn fix<A, B>(f: extern fn(fn@(A) -> B, A) -> B) -> fn@(A) -> B {
     return {|a|fix_help(f, a)};
 }
 
-fn fact_(f: fn@(&&int) -> int, &&n: int) -> int {
+fn fact_(f: fn@(&&v: int) -> int, &&n: int) -> int {
     // fun fact 0 = 1
     return if n == 0 { 1 } else { n * f(n - 1) };
 }

src/test/run-pass/fixed-point-bind-unique.rs

@@ -9,7 +9,7 @@ fn fix<A: Owned, B: Send>(f: extern fn(fn@(A) -> B, A) -> B) -> fn@(A) -> B {
     return {|a|fix_help(f, a)};
 }
 
-fn fact_(f: fn@(&&int) -> int, &&n: int) -> int {
+fn fact_(f: fn@(&&v: int) -> int, &&n: int) -> int {
     // fun fact 0 = 1
     return if n == 0 { 1 } else { n * f(n - 1) };
 }

src/test/run-pass/fn-bare-assign.rs

@@ -3,7 +3,7 @@ fn f(i: int, &called: bool) {
     called = true;
 }
 
-fn g(f: extern fn(int, &bool), &called: bool) {
+fn g(f: extern fn(int, &v: bool), &called: bool) {
     f(10, called);
 }
 

src/test/run-pass/generic-temporary.rs

@@ -12,6 +12,6 @@ fn apply<T>(produce: extern fn() -> T,
 
 fn main() {
     let produce: extern fn() -> int = mk;
-    let consume: extern fn(&&int) = chk;
+    let consume: extern fn(&&v: int) = chk;
     apply::<int>(produce, consume);
 }

src/test/run-pass/issue-2185.rs

@@ -14,7 +14,7 @@ impl<A> fn@(fn(A)): iterable<A> {
 }
 
 impl fn@(fn(uint)): iterable<uint> {
-    fn iter(blk: fn(&&uint)) { self( |i| blk(i) ) }
+    fn iter(blk: fn(&&v: uint)) { self( |i| blk(i) ) }
 }
 
 fn filter<A,IA:iterable<A>>(self: IA, prd: fn@(A) -> bool, blk: fn(A)) {
@@ -41,7 +41,7 @@ fn range(lo: uint, hi: uint, it: fn(uint)) {
 
 fn main() {
     let range: fn@(fn&(uint)) = |a| range(0u, 1000u, a);
-    let filt: fn@(fn&(&&uint)) = |a| filter(
+    let filt: fn@(fn&(&&v: uint)) = |a| filter(
         range,
         |&&n: uint| n % 3u != 0u && n % 5u != 0u,
         a);

src/test/run-pass/pipe-bank-proto.rs

@@ -37,7 +37,7 @@ macro_rules! move_it (
 )
 
 fn switch<T: Send, U>(+endp: pipes::RecvPacket<T>,
-                      f: fn(+Option<T>) -> U) -> U {
+                      f: fn(+v: Option<T>) -> U) -> U {
     f(pipes::try_recv(endp))
 }
 

src/test/run-pass/sendfn-generic-fn.rs

@@ -14,7 +14,7 @@ fn make_generic_record<A: Copy, B: Copy>(a: A, b: B) -> pair<A,B> {
     return {a: a, b: b};
 }
 
-fn test05_start(&&f: fn~(&&float, &&~str) -> pair<float, ~str>) {
+fn test05_start(&&f: fn~(&&v: float, &&v: ~str) -> pair<float, ~str>) {
     let p = f(22.22f, ~"Hi");
     log(debug, p);
     assert p.a == 22.22f;

src/test/run-pass/static-method-test.rs

@@ -26,27 +26,27 @@ impl int: bool_like {
 // A trait for sequences that can be constructed imperatively.
 trait buildable<A> {
      static pure fn build_sized(size: uint,
-                                builder: fn(push: pure fn(+A))) -> self;
+                                builder: fn(push: pure fn(+v: A))) -> self;
 }
 
 
 impl<A> @[A]: buildable<A> {
     #[inline(always)]
      static pure fn build_sized(size: uint,
-                                builder: fn(push: pure fn(+A))) -> @[A] {
+                                builder: fn(push: pure fn(+v: A))) -> @[A] {
          at_vec::build_sized(size, builder)
      }
 }
 impl<A> ~[A]: buildable<A> {
     #[inline(always)]
      static pure fn build_sized(size: uint,
-                                builder: fn(push: pure fn(+A))) -> ~[A] {
+                                builder: fn(push: pure fn(+v: A))) -> ~[A] {
          vec::build_sized(size, builder)
      }
 }
 
 #[inline(always)]
-pure fn build<A, B: buildable<A>>(builder: fn(push: pure fn(+A))) -> B {
+pure fn build<A, B: buildable<A>>(builder: fn(push: pure fn(+v: A))) -> B {
     build_sized(4, builder)
 }