auto merge of #20307 : nikomatsakis/rust/assoc-types-normalization-extend-bound, r=nrc

Rewrite associated types to use projection rather than dummy type parameters. This closes almost every (major) open issue, but I'm holding off on that until the code has landed and baked a bit. Probably it should have more tests, as well, but I wanted to get this landed as fast as possible so that we can collaborate on improving it.

The commit history is a little messy, particularly the merge commit at the end. If I get some time, I might just "reset" to the beginning and try to carve up the final state into logical pieces. Let me know if it seems hard to follow. By far the most crucial commit is "Implement associated type projection and normalization."

r? @nick29581

Author: bors

src/librustc/metadata/common.rs

@@ -256,3 +256,6 @@ pub const tag_predicate_space: uint = 0xa9;
 pub const tag_predicate_data: uint = 0xb0;
 
 pub const tag_unsafety: uint = 0xb1;
+
+pub const tag_associated_type_names: uint = 0xb2;
+pub const tag_associated_type_name: uint = 0xb3;

src/librustc/metadata/csearch.rs

@@ -226,7 +226,7 @@ pub fn get_struct_field_attrs(cstore: &cstore::CStore, def: ast::DefId) -> HashM
 
 pub fn get_type<'tcx>(tcx: &ty::ctxt<'tcx>,
                       def: ast::DefId)
-                      -> ty::Polytype<'tcx> {
+                      -> ty::TypeScheme<'tcx> {
     let cstore = &tcx.sess.cstore;
     let cdata = cstore.get_crate_data(def.krate);
     decoder::get_type(&*cdata, def.node, tcx)
@@ -239,7 +239,7 @@ pub fn get_trait_def<'tcx>(tcx: &ty::ctxt<'tcx>, def: ast::DefId) -> ty::TraitDe
 }
 
 pub fn get_field_type<'tcx>(tcx: &ty::ctxt<'tcx>, class_id: ast::DefId,
-                            def: ast::DefId) -> ty::Polytype<'tcx> {
+                            def: ast::DefId) -> ty::TypeScheme<'tcx> {
     let cstore = &tcx.sess.cstore;
     let cdata = cstore.get_crate_data(class_id.krate);
     let all_items = reader::get_doc(rbml::Doc::new(cdata.data()), tag_items);
@@ -257,7 +257,7 @@ pub fn get_field_type<'tcx>(tcx: &ty::ctxt<'tcx>, class_id: ast::DefId,
                     def)).to_string()
         });
     let ty = decoder::item_type(def, the_field, tcx, &*cdata);
-    ty::Polytype {
+    ty::TypeScheme {
         generics: ty::Generics::empty(),
         ty: ty,
     }

src/librustc/metadata/decoder.rs

@@ -172,14 +172,15 @@ fn item_visibility(item: rbml::Doc) -> ast::Visibility {
 }
 
 fn item_sort(item: rbml::Doc) -> char {
-    // NB(pcwalton): The default of 'r' here is relied upon in
-    // `is_associated_type` below.
-    let mut ret = 'r';
+    let mut ret = None;
     reader::tagged_docs(item, tag_item_trait_item_sort, |doc| {
-        ret = doc.as_str_slice().as_bytes()[0] as char;
+        ret = Some(doc.as_str_slice().as_bytes()[0] as char);
         false
     });
-    ret
+    match ret {
+        Some(r) => r,
+        None => panic!("No item_sort found")
+    }
 }
 
 fn item_symbol(item: rbml::Doc) -> String {
@@ -245,13 +246,13 @@ pub fn item_type<'tcx>(_item_id: ast::DefId, item: rbml::Doc,
 }
 
 fn doc_trait_ref<'tcx>(doc: rbml::Doc, tcx: &ty::ctxt<'tcx>, cdata: Cmd)
-                       -> ty::TraitRef<'tcx> {
+                       -> Rc<ty::TraitRef<'tcx>> {
     parse_trait_ref_data(doc.data, cdata.cnum, doc.start, tcx,
                          |_, did| translate_def_id(cdata, did))
 }
 
 fn item_trait_ref<'tcx>(doc: rbml::Doc, tcx: &ty::ctxt<'tcx>, cdata: Cmd)
-                        -> ty::TraitRef<'tcx> {
+                        -> Rc<ty::TraitRef<'tcx>> {
     let tp = reader::get_doc(doc, tag_item_trait_ref);
     doc_trait_ref(tp, tcx, cdata)
 }
@@ -369,6 +370,17 @@ fn parse_unsafety(item_doc: rbml::Doc) -> ast::Unsafety {
     }
 }
 
+fn parse_associated_type_names(item_doc: rbml::Doc) -> Vec<ast::Name> {
+    let names_doc = reader::get_doc(item_doc, tag_associated_type_names);
+    let mut names = Vec::new();
+    reader::tagged_docs(names_doc, tag_associated_type_name, |name_doc| {
+        let name = token::intern(name_doc.as_str_slice());
+        names.push(name);
+        true
+    });
+    names
+}
+
 pub fn get_trait_def<'tcx>(cdata: Cmd,
                            item_id: ast::NodeId,
                            tcx: &ty::ctxt<'tcx>) -> ty::TraitDef<'tcx>
@@ -377,17 +389,19 @@ pub fn get_trait_def<'tcx>(cdata: Cmd,
     let generics = doc_generics(item_doc, tcx, cdata, tag_item_generics);
     let bounds = trait_def_bounds(item_doc, tcx, cdata);
     let unsafety = parse_unsafety(item_doc);
+    let associated_type_names = parse_associated_type_names(item_doc);
 
     ty::TraitDef {
         unsafety: unsafety,
         generics: generics,
         bounds: bounds,
-        trait_ref: Rc::new(item_trait_ref(item_doc, tcx, cdata))
+        trait_ref: item_trait_ref(item_doc, tcx, cdata),
+        associated_type_names: associated_type_names,
     }
 }
 
 pub fn get_type<'tcx>(cdata: Cmd, id: ast::NodeId, tcx: &ty::ctxt<'tcx>)
-    -> ty::Polytype<'tcx> {
+    -> ty::TypeScheme<'tcx> {
 
     let item = lookup_item(id, cdata.data());
 
@@ -396,7 +410,7 @@ pub fn get_type<'tcx>(cdata: Cmd, id: ast::NodeId, tcx: &ty::ctxt<'tcx>)
 
     let generics = doc_generics(item, tcx, cdata, tag_item_generics);
 
-    ty::Polytype {
+    ty::TypeScheme {
         generics: generics,
         ty: t
     }
@@ -428,7 +442,7 @@ pub fn get_impl_trait<'tcx>(cdata: Cmd,
 {
     let item_doc = lookup_item(id, cdata.data());
     reader::maybe_get_doc(item_doc, tag_item_trait_ref).map(|tp| {
-        Rc::new(doc_trait_ref(tp, tcx, cdata))
+        doc_trait_ref(tp, tcx, cdata)
     })
 }
 
@@ -924,7 +938,7 @@ pub fn get_supertraits<'tcx>(cdata: Cmd, id: ast::NodeId, tcx: &ty::ctxt<'tcx>)
         // 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(Rc::new(trait_ref));
+            results.push(trait_ref);
         }
         true
     });
@@ -1353,7 +1367,7 @@ pub fn get_dylib_dependency_formats(cdata: Cmd)
         if spec.len() == 0 { continue }
         let cnum = spec.split(':').nth(0).unwrap();
         let link = spec.split(':').nth(1).unwrap();
-        let cnum = cnum.parse().unwrap();
+        let cnum: ast::CrateNum = cnum.parse().unwrap();
         let cnum = match cdata.cnum_map.get(&cnum) {
             Some(&n) => n,
             None => panic!("didn't find a crate in the cnum_map")

src/librustc/metadata/encoder.rs

@@ -142,7 +142,7 @@ fn encode_item_variances(rbml_w: &mut Encoder,
 
 fn encode_bounds_and_type<'a, 'tcx>(rbml_w: &mut Encoder,
                                     ecx: &EncodeContext<'a, 'tcx>,
-                                    pty: &ty::Polytype<'tcx>) {
+                                    pty: &ty::TypeScheme<'tcx>) {
     encode_generics(rbml_w, ecx, &pty.generics, tag_item_generics);
     encode_type(ecx, rbml_w, pty.ty);
 }
@@ -898,7 +898,10 @@ fn encode_info_for_associated_type(ecx: &EncodeContext,
     encode_visibility(rbml_w, associated_type.vis);
     encode_family(rbml_w, 'y');
     encode_parent_item(rbml_w, local_def(parent_id));
-    encode_item_sort(rbml_w, 'r');
+    encode_item_sort(rbml_w, 't');
+
+    let type_scheme = ty::lookup_item_type(ecx.tcx, associated_type.def_id);
+    encode_bounds_and_type(rbml_w, ecx, &type_scheme);
 
     let stab = stability::lookup(ecx.tcx, associated_type.def_id);
     encode_stability(rbml_w, stab);
@@ -1316,6 +1319,7 @@ fn encode_info_for_item(ecx: &EncodeContext,
         encode_item_variances(rbml_w, ecx, item.id);
         let trait_def = ty::lookup_trait_def(tcx, def_id);
         encode_unsafety(rbml_w, trait_def.unsafety);
+        encode_associated_type_names(rbml_w, trait_def.associated_type_names.as_slice());
         encode_generics(rbml_w, ecx, &trait_def.generics, tag_item_generics);
         encode_trait_ref(rbml_w, ecx, &*trait_def.trait_ref, tag_item_trait_ref);
         encode_name(rbml_w, item.ident.name);
@@ -1397,10 +1401,13 @@ fn encode_info_for_item(ecx: &EncodeContext,
                         ty::StaticExplicitSelfCategory;
                 }
                 ty::TypeTraitItem(associated_type) => {
+                    encode_name(rbml_w, associated_type.name);
+
                     let elem = ast_map::PathName(associated_type.name);
                     encode_path(rbml_w,
                                 path.clone().chain(Some(elem).into_iter()));
 
+                    encode_item_sort(rbml_w, 't');
                     encode_family(rbml_w, 'y');
 
                     is_nonstatic_method = false;
@@ -1689,6 +1696,14 @@ fn encode_unsafety(rbml_w: &mut Encoder, unsafety: ast::Unsafety) {
     rbml_w.wr_tagged_u8(tag_unsafety, byte);
 }
 
+fn encode_associated_type_names(rbml_w: &mut Encoder, names: &[ast::Name]) {
+    rbml_w.start_tag(tag_associated_type_names);
+    for &name in names.iter() {
+        rbml_w.wr_tagged_str(tag_associated_type_name, token::get_name(name).get());
+    }
+    rbml_w.end_tag();
+}
+
 fn encode_crate_deps(rbml_w: &mut Encoder, cstore: &cstore::CStore) {
     fn get_ordered_deps(cstore: &cstore::CStore) -> Vec<decoder::CrateDep> {
         // Pull the cnums and name,vers,hash out of cstore