Trait/fn bounds part 2: Inferred default bounds and looser restrictions on unbounded trait/fns.

src/libextra/io_util.rs

@@ -10,6 +10,7 @@
 
 use core::io::{Reader, BytesReader};
 use core::io;
+use core::cast;
 
 /// An implementation of the io::Reader interface which reads a buffer of bytes
 pub struct BufReader {
@@ -29,10 +30,13 @@ impl BufReader {
     }
 
     fn as_bytes_reader<A>(&self, f: &fn(&BytesReader) -> A) -> A {
+        // XXX FIXME(#5723)
+        let bytes = ::core::util::id::<&[u8]>(self.buf);
+        let bytes: &'static [u8] = unsafe { cast::transmute(bytes) };
         // Recreating the BytesReader state every call since
         // I can't get the borrowing to work correctly
         let bytes_reader = BytesReader {
-            bytes: ::core::util::id::<&[u8]>(self.buf),
+            bytes: bytes,
             pos: @mut *self.pos
         };
 

src/libextra/test.rs

@@ -423,7 +423,7 @@ type MonitorMsg = (TestDesc, TestResult);
 
 fn run_tests(opts: &TestOpts,
              tests: ~[TestDescAndFn],
-             callback: @fn(e: TestEvent)) {
+             callback: &fn(e: TestEvent)) {
 
     let filtered_tests = filter_tests(opts, tests);
     let filtered_descs = filtered_tests.map(|t| copy t.desc);

src/librustc/metadata/encoder.rs

@@ -959,7 +959,7 @@ fn encode_info_for_item(ecx: &EncodeContext,
         encode_attributes(ebml_w, item.attrs);
         match ty.node {
             ast::ty_path(path, bounds, _) if path.idents.len() == 1 => {
-                assert!(bounds.is_empty());
+                assert!(bounds.is_none());
                 encode_impl_type_basename(ecx, ebml_w,
                                           ast_util::path_to_ident(path));
             }

src/librustc/middle/kind.rs

@@ -128,7 +128,7 @@ fn check_item(item: @item, (cx, visitor): (Context, visit::vt<Context>)) {
                             // Yes, it's a destructor.
                             match self_type.node {
                                 ty_path(_, bounds, path_node_id) => {
-                                    assert!(bounds.is_empty());
+                                    assert!(bounds.is_none());
                                     let struct_def = cx.tcx.def_map.get_copy(
                                         &path_node_id);
                                     let struct_did =
@@ -169,10 +169,6 @@ fn with_appropriate_checker(cx: Context, id: node_id,
         let id = ast_util::def_id_of_def(fv.def).node;
         let var_t = ty::node_id_to_type(cx.tcx, id);
 
-        // FIXME(#3569): Once closure capabilities are restricted based on their
-        // incoming bounds, make this check conditional based on the bounds.
-        if !check_owned(cx, var_t, fv.span) { return; }
-
         // check that only immutable variables are implicitly copied in
         check_imm_free_var(cx, fv.def, fv.span);
 
@@ -184,10 +180,6 @@ fn with_appropriate_checker(cx: Context, id: node_id,
         let id = ast_util::def_id_of_def(fv.def).node;
         let var_t = ty::node_id_to_type(cx.tcx, id);
 
-        // FIXME(#3569): Once closure capabilities are restricted based on their
-        // incoming bounds, make this check conditional based on the bounds.
-        if !check_durable(cx.tcx, var_t, fv.span) { return; }
-
         // check that only immutable variables are implicitly copied in
         check_imm_free_var(cx, fv.def, fv.span);
 
@@ -293,9 +285,9 @@ pub fn check_expr(e: @expr, (cx, v): (Context, visit::vt<Context>)) {
         expr_cast(source, _) => {
             check_cast_for_escaping_regions(cx, source, e);
             match ty::get(ty::expr_ty(cx.tcx, e)).sty {
-                ty::ty_trait(_, _, store, _, bounds) => {
+                ty::ty_trait(_, _, _, _, bounds) => {
                     let source_ty = ty::expr_ty(cx.tcx, source);
-                    check_trait_cast_bounds(cx, e.span, source_ty, bounds, store)
+                    check_trait_cast_bounds(cx, e.span, source_ty, bounds)
                 }
                 _ => { }
             }
@@ -391,19 +383,14 @@ pub fn check_freevar_bounds(cx: Context, sp: span, ty: ty::t,
 }
 
 pub fn check_trait_cast_bounds(cx: Context, sp: span, ty: ty::t,
-                               bounds: ty::BuiltinBounds, store: ty::TraitStore) {
+                               bounds: ty::BuiltinBounds) {
     do check_builtin_bounds(cx, ty, bounds) |missing| {
         cx.tcx.sess.span_err(sp,
             fmt!("cannot pack type `%s`, which does not fulfill \
                   `%s`, as a trait bounded by %s",
                  ty_to_str(cx.tcx, ty), missing.user_string(cx.tcx),
                  bounds.user_string(cx.tcx)));
     }
-    // FIXME(#3569): Remove this check when the corresponding restriction
-    // is made with type contents.
-    if store == ty::UniqTraitStore && !ty::type_is_owned(cx.tcx, ty) {
-        cx.tcx.sess.span_err(sp, "uniquely-owned trait objects must be sendable");
-    }
 }
 
 fn is_nullary_variant(cx: Context, ex: @expr) -> bool {

src/librustc/middle/resolve.rs

@@ -4195,15 +4195,19 @@ impl Resolver {
                     }
                 }
 
-                for bounds.iter().advance |bound| {
-                    self.resolve_type_parameter_bound(bound, visitor);
-                }
+                do bounds.map |bound_vec| {
+                    for bound_vec.iter().advance |bound| {
+                        self.resolve_type_parameter_bound(bound, visitor);
+                    }
+                };
             }
 
             ty_closure(c) => {
-                for c.bounds.iter().advance |bound| {
-                    self.resolve_type_parameter_bound(bound, visitor);
-                }
+                do c.bounds.map |bounds| {
+                    for bounds.iter().advance |bound| {
+                        self.resolve_type_parameter_bound(bound, visitor);
+                    }
+                };
                 visit_ty(ty, ((), visitor));
             }
 

src/librustc/middle/ty.rs

@@ -2063,20 +2063,8 @@ pub fn type_contents(cx: ctxt, ty: t) -> TypeContents {
                 TC_MANAGED + statically_sized(nonowned(tc_mt(cx, mt, cache)))
             }
 
-            ty_trait(_, _, UniqTraitStore, _, _bounds) => {
-                // FIXME(#3569): Make this conditional on the trait's bounds.
-                TC_NONCOPY_TRAIT + TC_OWNED_POINTER
-            }
-
-            ty_trait(_, _, BoxTraitStore, mutbl, _bounds) => {
-                match mutbl {
-                    ast::m_mutbl => TC_MANAGED + TC_MUTABLE,
-                    _ => TC_MANAGED
-                }
-            }
-
-            ty_trait(_, _, RegionTraitStore(r), mutbl, _bounds) => {
-                borrowed_contents(r, mutbl)
+            ty_trait(_, _, store, mutbl, bounds) => {
+                trait_contents(store, mutbl, bounds)
             }
 
             ty_rptr(r, mt) => {
@@ -2261,23 +2249,59 @@ pub fn type_contents(cx: ctxt, ty: t) -> TypeContents {
     }
 
     fn closure_contents(cty: &ClosureTy) -> TypeContents {
+        // Closure contents are just like trait contents, but with potentially
+        // even more stuff.
         let st = match cty.sigil {
-            ast::BorrowedSigil => TC_BORROWED_POINTER,
-            ast::ManagedSigil => TC_MANAGED,
-            ast::OwnedSigil => if cty.bounds.contains_elem(BoundCopy) {
-                TC_OWNED_POINTER
-            } else {
-                TC_OWNED_POINTER + TC_NONCOPY_TRAIT
-            }
+            ast::BorrowedSigil =>
+                trait_contents(RegionTraitStore(cty.region), m_imm, cty.bounds)
+                    + TC_BORROWED_POINTER, // might be an env packet even if static
+            ast::ManagedSigil =>
+                trait_contents(BoxTraitStore, m_imm, cty.bounds),
+            ast::OwnedSigil =>
+                trait_contents(UniqTraitStore, m_imm, cty.bounds),
         };
+        // FIXME(#3569): This borrowed_contents call should be taken care of in
+        // trait_contents, after ~Traits and @Traits can have region bounds too.
+        // This one here is redundant for &fns but important for ~fns and @fns.
         let rt = borrowed_contents(cty.region, m_imm);
+        // This also prohibits "@once fn" from being copied, which allows it to
+        // be called. Neither way really makes much sense.
         let ot = match cty.onceness {
             ast::Once => TC_ONCE_CLOSURE,
             ast::Many => TC_NONE
         };
         st + rt + ot
     }
 
+    fn trait_contents(store: TraitStore, mutbl: ast::mutability,
+                      bounds: BuiltinBounds) -> TypeContents {
+        let st = match store {
+            UniqTraitStore      => TC_OWNED_POINTER,
+            BoxTraitStore       => TC_MANAGED,
+            RegionTraitStore(r) => borrowed_contents(r, mutbl),
+        };
+        let mt = match mutbl { ast::m_mutbl => TC_MUTABLE, _ => TC_NONE };
+        // We get additional "special type contents" for each bound that *isn't*
+        // on the trait. So iterate over the inverse of the bounds that are set.
+        // This is like with typarams below, but less "pessimistic" and also
+        // dependent on the trait store.
+        let mut bt = TC_NONE;
+        for (AllBuiltinBounds() - bounds).each |bound| {
+            bt = bt + match bound {
+                BoundCopy if store == UniqTraitStore
+                            => TC_NONCOPY_TRAIT,
+                BoundCopy   => TC_NONE, // @Trait/&Trait are copyable either way
+                BoundStatic if bounds.contains_elem(BoundOwned)
+                            => TC_NONE, // Owned bound implies static bound.
+                BoundStatic => TC_BORROWED_POINTER, // Useful for "@Trait:'static"
+                BoundOwned  => TC_NON_OWNED,
+                BoundConst  => TC_MUTABLE,
+                BoundSized  => TC_NONE, // don't care if interior is sized
+            };
+        }
+        st + mt + bt
+    }
+
     fn type_param_def_to_contents(cx: ctxt,
                                   type_param_def: &TypeParameterDef) -> TypeContents
     {
@@ -4497,7 +4521,9 @@ pub fn visitor_object_ty(tcx: ctxt) -> (@TraitRef, t) {
     };
     let trait_lang_item = tcx.lang_items.ty_visitor();
     let trait_ref = @TraitRef { def_id: trait_lang_item, substs: substs };
+    let mut static_trait_bound = EmptyBuiltinBounds();
+    static_trait_bound.add(BoundStatic);
     (trait_ref,
      mk_trait(tcx, trait_ref.def_id, copy trait_ref.substs,
-              BoxTraitStore, ast::m_imm, EmptyBuiltinBounds()))
+              BoxTraitStore, ast::m_imm, static_trait_bound))
 }

src/librustc/middle/typeck/astconv.rs

@@ -303,7 +303,7 @@ pub fn ast_ty_to_ty<AC:AstConv, RS:region_scope + Copy + 'static>(
                                 ty::BoxTraitStore
                             }
                         };
-                        let bounds = conv_builtin_bounds(this.tcx(), bounds);
+                        let bounds = conv_builtin_bounds(this.tcx(), bounds, trait_store);
                         return ty::mk_trait(tcx,
                                             result.def_id,
                                             copy result.substs,
@@ -386,7 +386,13 @@ pub fn ast_ty_to_ty<AC:AstConv, RS:region_scope + Copy + 'static>(
                                             bf.abis, &bf.lifetimes, &bf.decl))
       }
       ast::ty_closure(ref f) => {
-          let bounds = conv_builtin_bounds(this.tcx(), &f.bounds);
+          let bounds = conv_builtin_bounds(this.tcx(), &f.bounds, match f.sigil {
+              // Use corresponding trait store to figure out default bounds
+              // if none were specified.
+              ast::BorrowedSigil => ty::RegionTraitStore(ty::re_empty), // dummy region
+              ast::OwnedSigil    => ty::UniqTraitStore,
+              ast::ManagedSigil  => ty::BoxTraitStore,
+          });
           let fn_decl = ty_of_closure(this,
                                       rscope,
                                       f.sigil,
@@ -411,7 +417,7 @@ pub fn ast_ty_to_ty<AC:AstConv, RS:region_scope + Copy + 'static>(
         match a_def {
             // But don't emit the error if the user meant to do a trait anyway.
             ast::def_trait(*) => { },
-            _ if !bounds.is_empty() =>
+            _ if bounds.is_some() =>
                 tcx.sess.span_err(ast_ty.span,
                     "kind bounds can only be used on trait types"),
             _ => { },
@@ -741,41 +747,60 @@ pub fn ty_of_closure<AC:AstConv,RS:region_scope + Copy + 'static>(
     }
 }
 
-fn conv_builtin_bounds(tcx: ty::ctxt,
-                       ast_bounds: &OptVec<ast::TyParamBound>)
+fn conv_builtin_bounds(tcx: ty::ctxt, ast_bounds: &Option<OptVec<ast::TyParamBound>>,
+                       store: ty::TraitStore)
                        -> ty::BuiltinBounds {
     //! Converts a list of bounds from the AST into a `BuiltinBounds`
     //! struct. Reports an error if any of the bounds that appear
     //! in the AST refer to general traits and not the built-in traits
     //! like `Copy` or `Owned`. Used to translate the bounds that
     //! appear in closure and trait types, where only builtin bounds are
     //! legal.
-
-    let mut builtin_bounds = ty::EmptyBuiltinBounds();
-    for ast_bounds.iter().advance |ast_bound| {
-        match *ast_bound {
-            ast::TraitTyParamBound(b) => {
-                match lookup_def_tcx(tcx, b.path.span, b.ref_id) {
-                    ast::def_trait(trait_did) => {
-                        if try_add_builtin_trait(tcx,
-                                                 trait_did,
-                                                 &mut builtin_bounds) {
-                            loop; // success
+    //! If no bounds were specified, we choose a "default" bound based on
+    //! the allocation type of the fn/trait, as per issue #7264. The user can
+    //! override this with an empty bounds list, e.g. "~fn:()" or "~Trait:".
+
+    match (ast_bounds, store) {
+        (&Some(ref bound_vec), _) => {
+            let mut builtin_bounds = ty::EmptyBuiltinBounds();
+            for bound_vec.iter().advance |ast_bound| {
+                match *ast_bound {
+                    ast::TraitTyParamBound(b) => {
+                        match lookup_def_tcx(tcx, b.path.span, b.ref_id) {
+                            ast::def_trait(trait_did) => {
+                                if try_add_builtin_trait(tcx,
+                                                         trait_did,
+                                                         &mut builtin_bounds) {
+                                    loop; // success
+                                }
+                            }
+                            _ => { }
                         }
+                        tcx.sess.span_fatal(
+                            b.path.span,
+                            fmt!("only the builtin traits can be used \
+                                  as closure or object bounds"));
+                    }
+                    ast::RegionTyParamBound => {
+                        builtin_bounds.add(ty::BoundStatic);
                     }
-                    _ => { }
                 }
-                tcx.sess.span_fatal(
-                    b.path.span,
-                    fmt!("only the builtin traits can be used \
-                          as closure or object bounds"));
-            }
-            ast::RegionTyParamBound => {
-                builtin_bounds.add(ty::BoundStatic);
             }
+            builtin_bounds
+        },
+        // ~Trait is sugar for ~Trait:Owned.
+        (&None, ty::UniqTraitStore) => {
+            let mut set = ty::EmptyBuiltinBounds(); set.add(ty::BoundOwned); set
+        }
+        // @Trait is sugar for @Trait:'static.
+        // &'static Trait is sugar for &'static Trait:'static.
+        (&None, ty::BoxTraitStore) |
+        (&None, ty::RegionTraitStore(ty::re_static)) => {
+            let mut set = ty::EmptyBuiltinBounds(); set.add(ty::BoundStatic); set
         }
+        // &'r Trait is sugar for &'r Trait:<no-bounds>.
+        (&None, ty::RegionTraitStore(*)) => ty::EmptyBuiltinBounds(),
     }
-    builtin_bounds
 }
 
 pub fn try_add_builtin_trait(tcx: ty::ctxt,

src/libstd/io.rs

@@ -1042,12 +1042,14 @@ pub fn file_reader(path: &Path) -> Result<@Reader, ~str> {
 
 
 // Byte readers
-pub struct BytesReader<'self> {
-    bytes: &'self [u8],
+pub struct BytesReader {
+    // FIXME(#5723) see other FIXME below
+    // FIXME(#7268) this should also be parameterized over <'self>
+    bytes: &'static [u8],
     pos: @mut uint
 }
 
-impl<'self> Reader for BytesReader<'self> {
+impl Reader for BytesReader {
     fn read(&self, bytes: &mut [u8], len: uint) -> uint {
         let count = uint::min(len, self.bytes.len() - *self.pos);
 
@@ -1084,13 +1086,18 @@ impl<'self> Reader for BytesReader<'self> {
 }
 
 pub fn with_bytes_reader<T>(bytes: &[u8], f: &fn(@Reader) -> T) -> T {
+    // XXX XXX XXX this is glaringly unsound
+    // FIXME(#5723) Use a &Reader for the callback's argument. Should be:
+    // fn with_bytes_reader<'r, T>(bytes: &'r [u8], f: &fn(&'r Reader) -> T) -> T
+    let bytes: &'static [u8] = unsafe { cast::transmute(bytes) };
     f(@BytesReader {
         bytes: bytes,
         pos: @mut 0
     } as @Reader)
 }
 
 pub fn with_str_reader<T>(s: &str, f: &fn(@Reader) -> T) -> T {
+    // FIXME(#5723): As above.
     with_bytes_reader(s.as_bytes(), f)
 }