Allow traits to use builtin kinds as supertraits for rust-lang#7083.

Author: bblum

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

@@ -1076,6 +1076,9 @@ 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;
@@ -158,10 +159,16 @@ impl LanguageItems {
         }
     }
 
-    pub fn is_builtin_kind(&self, id: def_id) -> bool {
-        Some(id) == self.freeze_trait() ||
-        Some(id) == self.send_trait() ||
-        Some(id) == self.sized_trait()
+    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> {

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,
 }
 
@@ -3725,10 +3726,23 @@ pub fn impl_trait_ref(cx: ctxt, id: ast::def_id) -> Option<@TraitRef> {
     return ret;
 }
 
-pub fn trait_ref_is_builtin_kind(tcx: ctxt, tr: &ast::trait_ref) -> bool {
+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");
-    let def_id = ast_util::def_id_of_def(*def);
-    tcx.lang_items.is_builtin_kind(def_id)
+    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> {

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
-    }
-}

src/librustc/middle/typeck/collect.rs

@@ -398,28 +398,39 @@ pub fn ensure_supertraits(ccx: &CrateCtxt,
                           sp: codemap::span,
                           rp: Option<ty::region_variance>,
                           ast_trait_refs: &[ast::trait_ref],
-                          generics: &ast::Generics)
+                          generics: &ast::Generics) -> ty::BuiltinBounds
 {
     let tcx = ccx.tcx;
-    if tcx.supertraits.contains_key(&local_def(id)) { return; }
+
+    // Called only the first time trait_def_of_item is called.
+    // Supertraits are ensured at the same time.
+    assert!(!tcx.supertraits.contains_key(&local_def(id)));
 
     let self_ty = ty::mk_self(ccx.tcx, local_def(id));
     let mut ty_trait_refs: ~[@ty::TraitRef] = ~[];
+    let mut bounds = ty::EmptyBuiltinBounds();
     for ast_trait_ref in ast_trait_refs.iter() {
+        let trait_def_id = ty::trait_ref_to_def_id(ccx.tcx, ast_trait_ref);
+        // FIXME(#8559): Need to instantiate the trait_ref whether or not it's a
+        // builtin trait, so that the trait's node id appears in the tcx trait_ref
+        // map. This is only needed for metadata; see the similar fixme in encoder.rs.
         let trait_ref = instantiate_trait_ref(ccx, ast_trait_ref, rp,
                                               generics, self_ty);
-
-        // FIXME(#5527) Could have same trait multiple times
-        if ty_trait_refs.iter().any(|other_trait| other_trait.def_id == trait_ref.def_id) {
-            // This means a trait inherited from the same supertrait more
-            // than once.
-            tcx.sess.span_err(sp, "Duplicate supertrait in trait declaration");
-            break;
-        } else {
-            ty_trait_refs.push(trait_ref);
+        if !ty::try_add_builtin_trait(ccx.tcx, trait_def_id, &mut bounds) {
+
+            // FIXME(#5527) Could have same trait multiple times
+            if ty_trait_refs.iter().any(|other_trait| other_trait.def_id == trait_ref.def_id) {
+                // This means a trait inherited from the same supertrait more
+                // than once.
+                tcx.sess.span_err(sp, "Duplicate supertrait in trait declaration");
+                break;
+            } else {
+                ty_trait_refs.push(trait_ref);
+            }
         }
     }
     tcx.supertraits.insert(local_def(id), @ty_trait_refs);
+    bounds
 }
 
 /**
@@ -870,20 +881,19 @@ pub fn convert(ccx: &CrateCtxt, it: &ast::item) {
                                   parent_visibility);
         for t in opt_trait_ref.iter() {
             // Prevent the builtin kind traits from being manually implemented.
-            if ty::trait_ref_is_builtin_kind(ccx.tcx, t) {
-                ccx.tcx.sess.span_err(it.span,
+            let trait_def_id = ty::trait_ref_to_def_id(tcx, t);
+            if tcx.lang_items.to_builtin_kind(trait_def_id).is_some() {
+                tcx.sess.span_err(it.span,
                     "cannot provide an explicit implementation \
                      for a builtin kind");
             }
 
             check_methods_against_trait(ccx, generics, rp, selfty, t, cms);
         }
       }
-      ast::item_trait(ref generics, ref supertraits, ref trait_methods) => {
-          let trait_def = trait_def_of_item(ccx, it);
-          tcx.trait_defs.insert(local_def(it.id), trait_def);
+      ast::item_trait(ref generics, _, ref trait_methods) => {
+          let _trait_def = trait_def_of_item(ccx, it);
           ensure_trait_methods(ccx, it.id);
-          ensure_supertraits(ccx, it.id, it.span, rp, *supertraits, generics);
 
           let (_, provided_methods) =
               split_trait_methods(*trait_methods);
@@ -1039,13 +1049,16 @@ pub fn trait_def_of_item(ccx: &CrateCtxt, it: &ast::item) -> @ty::TraitDef {
     }
     let rp = tcx.region_paramd_items.find(&it.id).map_move(|x| *x);
     match it.node {
-        ast::item_trait(ref generics, _, _) => {
+        ast::item_trait(ref generics, ref supertraits, _) => {
             let self_ty = ty::mk_self(tcx, def_id);
             let (ty_generics, substs) = mk_item_substs(ccx, generics, rp,
                                                        Some(self_ty));
+            let bounds = ensure_supertraits(ccx, it.id, it.span, rp,
+                                            *supertraits, generics);
             let trait_ref = @ty::TraitRef {def_id: def_id,
                                            substs: substs};
             let trait_def = @ty::TraitDef {generics: ty_generics,
+                                           bounds: bounds,
                                            trait_ref: trait_ref};
             tcx.trait_defs.insert(def_id, trait_def);
             return trait_def;
@@ -1225,7 +1238,7 @@ pub fn ty_generics(ccx: &CrateCtxt,
                 TraitTyParamBound(ref b) => {
                     let ty = ty::mk_param(ccx.tcx, param_ty.idx, param_ty.def_id);
                     let trait_ref = instantiate_trait_ref(ccx, b, rp, generics, ty);
-                    if !astconv::try_add_builtin_trait(
+                    if !ty::try_add_builtin_trait(
                         ccx.tcx, trait_ref.def_id,
                         &mut param_bounds.builtin_bounds)
                     {