auto merge of #8562 : bblum/rust/superkinds, r=nikomatsakis

For #7083.

The metadata issue with the old version is now fixed. Ready for review.

This is also not the full solution to #7083, because this is not supported yet:
```
trait Foo : Send { }

impl <T: Send> Foo for T { }

fn foo<T: Foo>(val: T, chan: std::comm::Chan<T>) {
    chan.send(val);
}
```

cc @nikomatsakis

src/librustc/metadata/decoder.rs

@@ -375,9 +375,21 @@ pub fn get_trait_def(cdata: cmd,
     let tp_defs = item_ty_param_defs(item_doc, tcx, cdata,
                                      tag_items_data_item_ty_param_bounds);
     let rp = item_ty_region_param(item_doc);
+    let mut bounds = ty::EmptyBuiltinBounds();
+    // Collect the builtin bounds from the encoded supertraits.
+    // FIXME(#8559): They should be encoded directly.
+    do reader::tagged_docs(item_doc, tag_item_super_trait_ref) |trait_doc| {
+        // NB. Bypasses real supertraits. See get_supertraits() if you wanted them.
+        let trait_ref = doc_trait_ref(trait_doc, tcx, cdata);
+        do tcx.lang_items.to_builtin_kind(trait_ref.def_id).map_move |bound| {
+            bounds.add(bound);
+        };
+        true
+    };
     ty::TraitDef {
         generics: ty::Generics {type_param_defs: tp_defs,
                                 region_param: rp},
+        bounds: bounds,
         trait_ref: @item_trait_ref(item_doc, tcx, cdata)
     }
 }
@@ -929,7 +941,13 @@ pub fn get_supertraits(cdata: cmd, id: ast::NodeId, tcx: ty::ctxt)
     let mut results = ~[];
     let item_doc = lookup_item(id, cdata.data);
     do reader::tagged_docs(item_doc, tag_item_super_trait_ref) |trait_doc| {
-        results.push(@doc_trait_ref(trait_doc, tcx, cdata));
+        // NB. Only reads the ones that *aren't* builtin-bounds. See also
+        // get_trait_def() for collecting the builtin bounds.
+        // FIXME(#8559): The builtin bounds shouldn't be encoded in the first place.
+        let trait_ref = doc_trait_ref(trait_doc, tcx, cdata);
+        if tcx.lang_items.to_builtin_kind(trait_ref.def_id).is_none() {
+            results.push(@trait_ref);
+        }
         true
     };
     return results;

src/librustc/metadata/encoder.rs

@@ -1066,6 +1066,9 @@ fn encode_info_for_item(ecx: &EncodeContext,
             ebml_w.end_tag();
         }
         encode_path(ecx, ebml_w, path, ast_map::path_name(item.ident));
+        // FIXME(#8559): This should use the tcx's supertrait cache instead of
+        // reading the AST's list, because the former has already filtered out
+        // the builtin-kinds-as-supertraits. See corresponding fixme in decoder.
         for ast_trait_ref in super_traits.iter() {
             let trait_ref = ty::node_id_to_trait_ref(ecx.tcx, ast_trait_ref.ref_id);
             encode_trait_ref(ebml_w, ecx, trait_ref, tag_item_super_trait_ref);

src/librustc/middle/kind.rs

@@ -50,8 +50,6 @@ use syntax::visit::Visitor;
 // primitives in the stdlib are explicitly annotated to only take sendable
 // types.
 
-pub static try_adding: &'static str = "Try adding a move";
-
 #[deriving(Clone)]
 pub struct Context {
     tcx: ty::ctxt,
@@ -77,9 +75,6 @@ impl Visitor<Context> for KindAnalysisVisitor {
     fn visit_item(&mut self, i:@item, e:Context) {
         check_item(self, i, e);
     }
-    fn visit_block(&mut self, b:&Block, e:Context) {
-        check_block(self, b, e);
-    }
 }
 
 pub fn check_crate(tcx: ty::ctxt,
@@ -125,46 +120,47 @@ fn check_struct_safe_for_destructor(cx: Context,
     }
 }
 
-fn check_block(visitor: &mut KindAnalysisVisitor,
-               block: &Block,
-               cx: Context) {
-    visit::walk_block(visitor, block, cx);
+fn check_impl_of_trait(cx: Context, it: @item, trait_ref: &trait_ref, self_type: &Ty) {
+    let ast_trait_def = cx.tcx.def_map.find(&trait_ref.ref_id)
+                            .expect("trait ref not in def map!");
+    let trait_def_id = ast_util::def_id_of_def(*ast_trait_def);
+    let trait_def = cx.tcx.trait_defs.find(&trait_def_id)
+                        .expect("trait def not in trait-defs map!");
+
+    // If this trait has builtin-kind supertraits, meet them.
+    let self_ty: ty::t = ty::node_id_to_type(cx.tcx, it.id);
+    error!("checking impl with self type %?", ty::get(self_ty).sty);
+    do check_builtin_bounds(cx, self_ty, trait_def.bounds) |missing| {
+        cx.tcx.sess.span_err(self_type.span,
+            fmt!("the type `%s', which does not fulfill `%s`, cannot implement this \
+                  trait", ty_to_str(cx.tcx, self_ty), missing.user_string(cx.tcx)));
+        cx.tcx.sess.span_note(self_type.span,
+            fmt!("types implementing this trait must fulfill `%s`",
+                 trait_def.bounds.user_string(cx.tcx)));
+    }
+
+    // If this is a destructor, check kinds.
+    if cx.tcx.lang_items.drop_trait() == Some(trait_def_id) {
+        match self_type.node {
+            ty_path(_, ref bounds, path_node_id) => {
+                assert!(bounds.is_none());
+                let struct_def = cx.tcx.def_map.get_copy(&path_node_id);
+                let struct_did = ast_util::def_id_of_def(struct_def);
+                check_struct_safe_for_destructor(cx, self_type.span, struct_did);
+            }
+            _ => {
+                cx.tcx.sess.span_bug(self_type.span,
+                    "the self type for the Drop trait impl is not a path");
+            }
+        }
+    }
 }
 
 fn check_item(visitor: &mut KindAnalysisVisitor, item: @item, cx: Context) {
-    // If this is a destructor, check kinds.
     if !attr::contains_name(item.attrs, "unsafe_destructor") {
         match item.node {
             item_impl(_, Some(ref trait_ref), ref self_type, _) => {
-                match cx.tcx.def_map.find(&trait_ref.ref_id) {
-                    None => cx.tcx.sess.bug("trait ref not in def map!"),
-                    Some(&trait_def) => {
-                        let trait_def_id = ast_util::def_id_of_def(trait_def);
-                        if cx.tcx.lang_items.drop_trait() == Some(trait_def_id) {
-                            // Yes, it's a destructor.
-                            match self_type.node {
-                                ty_path(_, ref bounds, path_node_id) => {
-                                    assert!(bounds.is_none());
-                                    let struct_def = cx.tcx.def_map.get_copy(
-                                        &path_node_id);
-                                    let struct_did =
-                                        ast_util::def_id_of_def(struct_def);
-                                    check_struct_safe_for_destructor(
-                                        cx,
-                                        self_type.span,
-                                        struct_did);
-                                }
-                                _ => {
-                                    cx.tcx.sess.span_bug(self_type.span,
-                                                         "the self type for \
-                                                          the Drop trait \
-                                                          impl is not a \
-                                                          path");
-                                }
-                            }
-                        }
-                    }
-                }
+                check_impl_of_trait(cx, item, trait_ref, self_type);
             }
             _ => {}
         }

src/librustc/middle/lang_items.rs

@@ -23,6 +23,7 @@
 use driver::session::Session;
 use metadata::csearch::each_lang_item;
 use metadata::cstore::iter_crate_data;
+use middle::ty::{BuiltinBound, BoundFreeze, BoundSend, BoundSized};
 use syntax::ast::{Crate, def_id, MetaItem};
 use syntax::ast_util::local_def;
 use syntax::attr::AttrMetaMethods;
@@ -158,6 +159,18 @@ impl LanguageItems {
         }
     }
 
+    pub fn to_builtin_kind(&self, id: def_id) -> Option<BuiltinBound> {
+        if Some(id) == self.freeze_trait() {
+            Some(BoundFreeze)
+        } else if Some(id) == self.send_trait() {
+            Some(BoundSend)
+        } else if Some(id) == self.sized_trait() {
+            Some(BoundSized)
+        } else {
+            None
+        }
+    }
+
     pub fn freeze_trait(&self) -> Option<def_id> {
         self.items[FreezeTraitLangItem as uint]
     }

src/librustc/middle/ty.rs

@@ -863,6 +863,7 @@ pub struct ty_param_bounds_and_ty {
 /// As `ty_param_bounds_and_ty` but for a trait ref.
 pub struct TraitDef {
     generics: Generics,
+    bounds: BuiltinBounds,
     trait_ref: @ty::TraitRef,
 }
 
@@ -2160,17 +2161,19 @@ pub fn type_contents(cx: ctxt, ty: t) -> TypeContents {
                 // def-id.
                 assert_eq!(p.def_id.crate, ast::LOCAL_CRATE);
 
-                type_param_def_to_contents(
-                    cx, cx.ty_param_defs.get(&p.def_id.node))
+                let tp_def = cx.ty_param_defs.get(&p.def_id.node);
+                kind_bounds_to_contents(cx, &tp_def.bounds.builtin_bounds,
+                                        tp_def.bounds.trait_bounds)
             }
 
-            ty_self(_) => {
-                // Currently, self is not bounded, so we must assume the
-                // worst.  But in the future we should examine the super
-                // traits.
-                //
+            ty_self(def_id) => {
                 // FIXME(#4678)---self should just be a ty param
-                TC_ALL
+
+                // Self may be bounded if the associated trait has builtin kinds
+                // for supertraits. If so we can use those bounds.
+                let trait_def = lookup_trait_def(cx, def_id);
+                let traits = [trait_def.trait_ref];
+                kind_bounds_to_contents(cx, &trait_def.bounds, traits)
             }
 
             ty_infer(_) => {
@@ -2314,14 +2317,12 @@ pub fn type_contents(cx: ctxt, ty: t) -> TypeContents {
         st + mt + bt
     }
 
-    fn type_param_def_to_contents(cx: ctxt,
-                                  type_param_def: &TypeParameterDef) -> TypeContents
-    {
-        debug!("type_param_def_to_contents(%s)", type_param_def.repr(cx));
+    fn kind_bounds_to_contents(cx: ctxt, bounds: &BuiltinBounds, traits: &[@TraitRef])
+            -> TypeContents {
         let _i = indenter();
 
         let mut tc = TC_ALL;
-        for bound in type_param_def.bounds.builtin_bounds.iter() {
+        do each_inherited_builtin_bound(cx, bounds, traits) |bound| {
             debug!("tc = %s, bound = %?", tc.to_str(), bound);
             tc = tc - match bound {
                 BoundStatic => TypeContents::nonstatic(cx),
@@ -2334,6 +2335,23 @@ pub fn type_contents(cx: ctxt, ty: t) -> TypeContents {
 
         debug!("result = %s", tc.to_str());
         return tc;
+
+        // Iterates over all builtin bounds on the type parameter def, including
+        // those inherited from traits with builtin-kind-supertraits.
+        fn each_inherited_builtin_bound(cx: ctxt, bounds: &BuiltinBounds,
+                                        traits: &[@TraitRef], f: &fn(BuiltinBound)) {
+            for bound in bounds.iter() {
+                f(bound);
+            }
+
+            do each_bound_trait_and_supertraits(cx, traits) |trait_ref| {
+                let trait_def = lookup_trait_def(cx, trait_ref.def_id);
+                for bound in trait_def.bounds.iter() {
+                    f(bound);
+                }
+                true
+            };
+        }
     }
 }
 
@@ -3727,6 +3745,25 @@ pub fn impl_trait_ref(cx: ctxt, id: ast::def_id) -> Option<@TraitRef> {
     return ret;
 }
 
+pub fn trait_ref_to_def_id(tcx: ctxt, tr: &ast::trait_ref) -> ast::def_id {
+    let def = tcx.def_map.find(&tr.ref_id).expect("no def-map entry for trait");
+    ast_util::def_id_of_def(*def)
+}
+
+pub fn try_add_builtin_trait(tcx: ctxt,
+                             trait_def_id: ast::def_id,
+                             builtin_bounds: &mut BuiltinBounds) -> bool {
+    //! Checks whether `trait_ref` refers to one of the builtin
+    //! traits, like `Send`, and adds the corresponding
+    //! bound to the set `builtin_bounds` if so. Returns true if `trait_ref`
+    //! is a builtin trait.
+
+    match tcx.lang_items.to_builtin_kind(trait_def_id) {
+        Some(bound) => { builtin_bounds.add(bound); true }
+        None => false
+    }
+}
+
 pub fn ty_to_def_id(ty: t) -> Option<ast::def_id> {
     match get(ty).sty {
       ty_trait(id, _, _, _, _) | ty_struct(id, _) | ty_enum(id, _) => Some(id),

src/librustc/middle/typeck/astconv.rs

@@ -773,9 +773,8 @@ fn conv_builtin_bounds(tcx: ty::ctxt, ast_bounds: &Option<OptVec<ast::TyParamBou
                     ast::TraitTyParamBound(ref 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) {
+                                if ty::try_add_builtin_trait(tcx, trait_did,
+                                                             &mut builtin_bounds) {
                                     loop; // success
                                 }
                             }
@@ -807,26 +806,3 @@ fn conv_builtin_bounds(tcx: ty::ctxt, ast_bounds: &Option<OptVec<ast::TyParamBou
         (&None, ty::RegionTraitStore(*)) => ty::EmptyBuiltinBounds(),
     }
 }
-
-pub fn try_add_builtin_trait(tcx: ty::ctxt,
-                             trait_def_id: ast::def_id,
-                             builtin_bounds: &mut ty::BuiltinBounds) -> bool {
-    //! Checks whether `trait_ref` refers to one of the builtin
-    //! traits, like `Send`, and adds the corresponding
-    //! bound to the set `builtin_bounds` if so. Returns true if `trait_ref`
-    //! is a builtin trait.
-
-    let li = &tcx.lang_items;
-    if Some(trait_def_id) == li.send_trait() {
-        builtin_bounds.add(ty::BoundSend);
-        true
-    } else if Some(trait_def_id) == li.freeze_trait() {
-        builtin_bounds.add(ty::BoundFreeze);
-        true
-    } else if Some(trait_def_id) == li.sized_trait() {
-        builtin_bounds.add(ty::BoundSized);
-        true
-    } else {
-        false
-    }
-}