Implement unique types per fn item, rather than having all fn items have fn pointer type

src/libcollections/btree/map.rs

@@ -1230,6 +1230,7 @@ impl<K, V> BTreeMap<K, V> {
     #[unstable = "matches collection reform specification, waiting for dust to settle"]
     pub fn keys<'a>(&'a self) -> Keys<'a, K, V> {
         fn first<A, B>((a, _): (A, B)) -> A { a }
+        let first: fn((&'a K, &'a V)) -> &'a K = first; // coerce to fn pointer
 
         Keys { inner: self.iter().map(first) }
     }
@@ -1251,6 +1252,7 @@ impl<K, V> BTreeMap<K, V> {
     #[unstable = "matches collection reform specification, waiting for dust to settle"]
     pub fn values<'a>(&'a self) -> Values<'a, K, V> {
         fn second<A, B>((_, b): (A, B)) -> B { b }
+        let second: fn((&'a K, &'a V)) -> &'a V = second; // coerce to fn pointer
 
         Values { inner: self.iter().map(second) }
     }

src/libcollections/btree/set.rs

@@ -126,6 +126,7 @@ impl<T> BTreeSet<T> {
     #[unstable = "matches collection reform specification, waiting for dust to settle"]
     pub fn into_iter(self) -> MoveItems<T> {
         fn first<A, B>((a, _): (A, B)) -> A { a }
+        let first: fn((T, ())) -> T = first; // coerce to fn pointer
 
         MoveItems { iter: self.map.into_iter().map(first) }
     }

src/libcollections/vec_map.rs

@@ -144,6 +144,7 @@ impl<V> VecMap<V> {
     #[unstable = "matches collection reform specification, waiting for dust to settle"]
     pub fn keys<'r>(&'r self) -> Keys<'r, V> {
         fn first<A, B>((a, _): (A, B)) -> A { a }
+        let first: fn((uint, &'r V)) -> uint = first; // coerce to fn pointer
 
         Keys { iter: self.iter().map(first) }
     }
@@ -153,6 +154,7 @@ impl<V> VecMap<V> {
     #[unstable = "matches collection reform specification, waiting for dust to settle"]
     pub fn values<'r>(&'r self) -> Values<'r, V> {
         fn second<A, B>((_, b): (A, B)) -> B { b }
+        let second: fn((uint, &'r V)) -> &'r V = second; // coerce to fn pointer
 
         Values { iter: self.iter().map(second) }
     }
@@ -239,6 +241,7 @@ impl<V> VecMap<V> {
         fn filter<A>((i, v): (uint, Option<A>)) -> Option<(uint, A)> {
             v.map(|v| (i, v))
         }
+        let filter: fn((uint, Option<V>)) -> Option<(uint, V)> = filter; // coerce to fn ptr
 
         let values = replace(&mut self.v, vec!());
         MoveItems { iter: values.into_iter().enumerate().filter_map(filter) }

src/libcore/iter.rs

@@ -2612,6 +2612,9 @@ pub fn iterate<T, F>(seed: T, f: F) -> Iterate<T, F> where
         val.clone()
     }
 
+    // coerce to a fn pointer
+    let next: fn(&mut IterateState<T,F>) -> Option<T> = next;
+
     Unfold::new((f, Some(seed), true), next)
 }
 

src/libcore/str.rs

@@ -30,9 +30,9 @@ use iter::range;
 use kinds::Sized;
 use mem;
 use num::Int;
+use ops::{Fn, FnMut};
 use option::Option;
 use option::Option::{None, Some};
-use ops::{Fn, FnMut};
 use ptr::RawPtr;
 use raw::{Repr, Slice};
 use slice::{mod, SliceExt};
@@ -2100,6 +2100,7 @@ impl StrPrelude for str {
             else { line }
         }
 
+        let f: fn(&str) -> &str = f; // coerce to fn pointer
         self.lines().map(f)
     }
 

src/librustc/metadata/decoder.rs

@@ -700,7 +700,7 @@ pub fn get_enum_variants<'tcx>(intr: Rc<IdentInterner>, cdata: Cmd, id: ast::Nod
                                 item, tcx, cdata);
         let name = item_name(&*intr, item);
         let (ctor_ty, arg_tys, arg_names) = match ctor_ty.sty {
-            ty::ty_bare_fn(ref f) =>
+            ty::ty_bare_fn(_, ref f) =>
                 (Some(ctor_ty), f.sig.0.inputs.clone(), None),
             _ => { // Nullary or struct enum variant.
                 let mut arg_names = Vec::new();

src/librustc/metadata/tydecode.rs

@@ -453,7 +453,11 @@ fn parse_ty<'a, 'tcx>(st: &mut PState<'a, 'tcx>, conv: conv_did) -> Ty<'tcx> {
         return ty::mk_closure(st.tcx, parse_closure_ty(st, |x,y| conv(x,y)));
       }
       'F' => {
-        return ty::mk_bare_fn(st.tcx, parse_bare_fn_ty(st, |x,y| conv(x,y)));
+          let def_id = parse_def(st, NominalType, |x,y| conv(x,y));
+          return ty::mk_bare_fn(st.tcx, Some(def_id), parse_bare_fn_ty(st, |x,y| conv(x,y)));
+      }
+      'G' => {
+          return ty::mk_bare_fn(st.tcx, None, parse_bare_fn_ty(st, |x,y| conv(x,y)));
       }
       '#' => {
         let pos = parse_hex(st);

src/librustc/metadata/tyencode.rs

@@ -123,8 +123,13 @@ pub fn enc_ty<'a, 'tcx>(w: &mut SeekableMemWriter, cx: &ctxt<'a, 'tcx>, t: Ty<'t
             mywrite!(w, "f");
             enc_closure_ty(w, cx, &**f);
         }
-        ty::ty_bare_fn(ref f) => {
+        ty::ty_bare_fn(Some(def_id), ref f) => {
             mywrite!(w, "F");
+            mywrite!(w, "{}|", (cx.ds)(def_id));
+            enc_bare_fn_ty(w, cx, f);
+        }
+        ty::ty_bare_fn(None, ref f) => {
+            mywrite!(w, "G");
             enc_bare_fn_ty(w, cx, f);
         }
         ty::ty_infer(_) => {

src/librustc/middle/astencode.rs

@@ -1007,14 +1007,21 @@ impl<'a, 'tcx> rbml_writer_helpers<'tcx> for Encoder<'a> {
 
         self.emit_enum("AutoAdjustment", |this| {
             match *adj {
-                ty::AdjustAddEnv(store) => {
-                    this.emit_enum_variant("AutoAddEnv", 0, 1, |this| {
-                        this.emit_enum_variant_arg(0, |this| store.encode(this))
+                ty::AdjustAddEnv(def_id, store) => {
+                    this.emit_enum_variant("AdjustAddEnv", 0, 2, |this| {
+                        this.emit_enum_variant_arg(0, |this| def_id.encode(this));
+                        this.emit_enum_variant_arg(1, |this| store.encode(this))
+                    })
+                }
+
+                ty::AdjustReifyFnPointer(def_id) => {
+                    this.emit_enum_variant("AdjustReifyFnPointer", 1, 2, |this| {
+                        this.emit_enum_variant_arg(0, |this| def_id.encode(this))
                     })
                 }
 
                 ty::AdjustDerefRef(ref auto_deref_ref) => {
-                    this.emit_enum_variant("AutoDerefRef", 1, 1, |this| {
+                    this.emit_enum_variant("AdjustDerefRef", 2, 2, |this| {
                         this.emit_enum_variant_arg(0,
                             |this| Ok(this.emit_auto_deref_ref(ecx, auto_deref_ref)))
                     })
@@ -1648,12 +1655,20 @@ impl<'a, 'tcx> rbml_decoder_decoder_helpers<'tcx> for reader::Decoder<'a> {
             this.read_enum_variant(&variants, |this, i| {
                 Ok(match i {
                     0 => {
+                        let def_id: ast::DefId =
+                            this.read_def_id(dcx);
                         let store: ty::TraitStore =
                             this.read_enum_variant_arg(0, |this| Decodable::decode(this)).unwrap();
 
-                        ty::AdjustAddEnv(store.tr(dcx))
+                        ty::AdjustAddEnv(def_id, store.tr(dcx))
                     }
                     1 => {
+                        let def_id: ast::DefId =
+                            this.read_def_id(dcx);
+
+                        ty::AdjustReifyFnPointer(def_id)
+                    }
+                    2 => {
                         let auto_deref_ref: ty::AutoDerefRef =
                             this.read_enum_variant_arg(0,
                                 |this| Ok(this.read_auto_deref_ref(dcx))).unwrap();

src/librustc/middle/check_const.rs

@@ -127,7 +127,11 @@ fn check_expr(v: &mut CheckCrateVisitor, e: &ast::Expr) -> bool {
         ast::ExprCast(ref from, _) => {
             let toty = ty::expr_ty(v.tcx, e);
             let fromty = ty::expr_ty(v.tcx, &**from);
-            if !ty::type_is_numeric(toty) && !ty::type_is_unsafe_ptr(toty) {
+            let is_legal_cast =
+                ty::type_is_numeric(toty) ||
+                ty::type_is_unsafe_ptr(toty) ||
+                (ty::type_is_bare_fn(toty) && ty::type_is_bare_fn_item(fromty));
+            if !is_legal_cast {
                 span_err!(v.tcx.sess, e.span, E0012,
                           "can not cast to `{}` in a constant expression",
                           ppaux::ty_to_string(v.tcx, toty));

src/librustc/middle/effect.rs

@@ -32,7 +32,7 @@ enum UnsafeContext {
 
 fn type_is_unsafe_function(ty: Ty) -> bool {
     match ty.sty {
-        ty::ty_bare_fn(ref f) => f.unsafety == ast::Unsafety::Unsafe,
+        ty::ty_bare_fn(_, ref f) => f.unsafety == ast::Unsafety::Unsafe,
         ty::ty_closure(ref f) => f.unsafety == ast::Unsafety::Unsafe,
         _ => false,
     }

src/librustc/middle/expr_use_visitor.rs

@@ -824,10 +824,12 @@ impl<'d,'t,'tcx,TYPER:mc::Typer<'tcx>> ExprUseVisitor<'d,'t,'tcx,TYPER> {
             None => { }
             Some(adjustment) => {
                 match *adjustment {
-                    ty::AdjustAddEnv(..) => {
-                        // Creating a closure consumes the input and stores it
-                        // into the resulting rvalue.
-                        debug!("walk_adjustment(AutoAddEnv)");
+                    ty::AdjustAddEnv(..) |
+                    ty::AdjustReifyFnPointer(..) => {
+                        // Creating a closure/fn-pointer consumes the
+                        // input and stores it into the resulting
+                        // rvalue.
+                        debug!("walk_adjustment(AutoAddEnv|AdjustReifyFnPointer)");
                         let cmt_unadjusted =
                             return_if_err!(self.mc.cat_expr_unadjusted(expr));
                         self.delegate_consume(expr.id, expr.span, cmt_unadjusted);

src/librustc/middle/fast_reject.rs

@@ -83,7 +83,7 @@ pub fn simplify_type(tcx: &ty::ctxt,
         ty::ty_closure(ref f) => {
             Some(FunctionSimplifiedType(f.sig.0.inputs.len()))
         }
-        ty::ty_bare_fn(ref f) => {
+        ty::ty_bare_fn(_, ref f) => {
             Some(FunctionSimplifiedType(f.sig.0.inputs.len()))
         }
         ty::ty_param(_) => {