librustc: Implement basic lazy implementation loading.

This is only for implementations defined in the same crate as the trait they
implement.

src/librustc/metadata/common.rs

@@ -185,6 +185,9 @@ pub static tag_item_impl_vtables: uint = 0x82;
 pub static tag_impls: uint = 0x83;
 pub static tag_impls_impl: uint = 0x84;
 
+pub static tag_items_data_item_inherent_impl: uint = 0x85;
+pub static tag_items_data_item_extension_impl: uint = 0x86;
+
 pub struct LinkMeta {
     name: @str,
     vers: @str,

src/librustc/metadata/csearch.rs

@@ -272,3 +272,28 @@ pub fn each_impl(cstore: @mut cstore::CStore,
     decoder::each_impl(cdata, callback)
 }
 
+pub fn each_implementation_for_type(cstore: @mut cstore::CStore,
+                                    def_id: ast::def_id,
+                                    callback: &fn(ast::def_id)) {
+    let cdata = cstore::get_crate_data(cstore, def_id.crate);
+    decoder::each_implementation_for_type(cdata, def_id.node, callback)
+}
+
+pub fn each_implementation_for_trait(cstore: @mut cstore::CStore,
+                                     def_id: ast::def_id,
+                                     callback: &fn(ast::def_id)) {
+    let cdata = cstore::get_crate_data(cstore, def_id.crate);
+    decoder::each_implementation_for_trait(cdata, def_id.node, callback)
+}
+
+/// If the given def ID describes a method belonging to a trait (either a
+/// default method or an implementation of a trait method), returns the ID of
+/// the trait that the method belongs to. Otherwise, returns `None`.
+pub fn get_trait_of_method(cstore: @mut cstore::CStore,
+                           def_id: ast::def_id,
+                           tcx: ty::ctxt)
+                           -> Option<ast::def_id> {
+    let cdata = cstore::get_crate_data(cstore, def_id.crate);
+    decoder::get_trait_of_method(cdata, def_id.node, tcx)
+}
+

src/librustc/metadata/decoder.rs

@@ -20,6 +20,7 @@ use metadata::decoder;
 use metadata::tydecode::{parse_ty_data, parse_def_id,
                          parse_type_param_def_data,
                          parse_bare_fn_ty_data, parse_trait_ref_data};
+use middle::ty::{ImplContainer, TraitContainer};
 use middle::ty;
 use middle::typeck;
 use middle::astencode::vtable_decoder_helpers;
@@ -958,8 +959,15 @@ pub fn get_method(intr: @ident_interner, cdata: cmd, id: ast::NodeId,
 {
     let method_doc = lookup_item(id, cdata.data);
     let def_id = item_def_id(method_doc, cdata);
+
     let container_id = item_reqd_and_translated_parent_item(cdata.cnum,
                                                             method_doc);
+    let container_doc = lookup_item(container_id.node, cdata.data);
+    let container = match item_family(container_doc) {
+        Trait => TraitContainer(container_id),
+        _ => ImplContainer(container_id),
+    };
+
     let name = item_name(intr, method_doc);
     let type_param_defs = item_ty_param_defs(method_doc, tcx, cdata,
                                              tag_item_method_tps);
@@ -980,7 +988,7 @@ pub fn get_method(intr: @ident_interner, cdata: cmd, id: ast::NodeId,
         explicit_self,
         vis,
         def_id,
-        container_id,
+        container,
         provided_source
     )
 }
@@ -1391,4 +1399,56 @@ pub fn each_impl(cdata: cmd, callback: &fn(ast::def_id)) {
     };
 }
 
+pub fn each_implementation_for_type(cdata: cmd,
+                                    id: ast::NodeId,
+                                    callback: &fn(ast::def_id)) {
+    let item_doc = lookup_item(id, cdata.data);
+    /*println(fmt!(">>> reading inherent impls from %s",
+                 token::ident_to_str(&item_name(token::get_ident_interner(),
+                                                item_doc))));*/
+    do reader::tagged_docs(item_doc, tag_items_data_item_inherent_impl)
+            |impl_doc| {
+        let implementation_def_id = item_def_id(impl_doc, cdata);
+        /*println(fmt!(">>>>> read inherent impl: %d:%d",
+                     implementation_def_id.crate,
+                     implementation_def_id.node));*/
+        callback(implementation_def_id);
+        true
+    };
+}
+
+pub fn each_implementation_for_trait(cdata: cmd,
+                                     id: ast::NodeId,
+                                     callback: &fn(ast::def_id)) {
+    let item_doc = lookup_item(id, cdata.data);
+
+    let _ = do reader::tagged_docs(item_doc,
+                                   tag_items_data_item_extension_impl)
+            |impl_doc| {
+        let implementation_def_id = item_def_id(impl_doc, cdata);
+        callback(implementation_def_id);
+        true
+    };
+}
+
+pub fn get_trait_of_method(cdata: cmd, id: ast::NodeId, tcx: ty::ctxt)
+                           -> Option<ast::def_id> {
+    let item_doc = lookup_item(id, cdata.data);
+    let parent_item_id = match item_parent_item(item_doc) {
+        None => return None,
+        Some(item_id) => item_id,
+    };
+    let parent_item_id = translate_def_id(cdata, parent_item_id);
+    let parent_item_doc = lookup_item(parent_item_id.node, cdata.data);
+    match item_family(parent_item_doc) {
+        Trait => Some(item_def_id(parent_item_doc, cdata)),
+        Impl => {
+            do reader::maybe_get_doc(parent_item_doc, tag_item_trait_ref).map
+                    |_| {
+                item_trait_ref(parent_item_doc, tcx, cdata).def_id
+            }
+        }
+        _ => None
+    }
+}
 

src/librustc/metadata/encoder.rs

@@ -799,6 +799,38 @@ fn should_inline(attrs: &[Attribute]) -> bool {
     }
 }
 
+// Encodes the inherent implementations of a structure, enumeration, or trait.
+fn encode_inherent_implementations(ecx: &EncodeContext,
+                                   ebml_w: &mut writer::Encoder,
+                                   def_id: def_id) {
+    match ecx.tcx.inherent_impls.find(&def_id) {
+        None => {}
+        Some(&implementations) => {
+            for implementation in implementations.iter() {
+                ebml_w.start_tag(tag_items_data_item_inherent_impl);
+                encode_def_id(ebml_w, implementation.did);
+                ebml_w.end_tag();
+            }
+        }
+    }
+}
+
+// Encodes the implementations of a trait defined in this crate.
+fn encode_extension_implementations(ecx: &EncodeContext,
+                                    ebml_w: &mut writer::Encoder,
+                                    trait_def_id: def_id) {
+    match ecx.tcx.trait_impls.find(&trait_def_id) {
+        None => {}
+        Some(&implementations) => {
+            for implementation in implementations.iter() {
+                ebml_w.start_tag(tag_items_data_item_extension_impl);
+                encode_def_id(ebml_w, implementation.did);
+                ebml_w.end_tag();
+            }
+        }
+    }
+}
+
 fn encode_info_for_item(ecx: &EncodeContext,
                         ebml_w: &mut writer::Encoder,
                         item: @item,
@@ -902,6 +934,10 @@ fn encode_info_for_item(ecx: &EncodeContext,
         (ecx.encode_inlined_item)(ecx, ebml_w, path, ii_item(item));
         encode_path(ecx, ebml_w, path, ast_map::path_name(item.ident));
         encode_region_param(ecx, ebml_w, item);
+
+        // Encode inherent implementations for this enumeration.
+        encode_inherent_implementations(ecx, ebml_w, def_id);
+
         ebml_w.end_tag();
 
         encode_enum_variant_info(ecx,
@@ -954,6 +990,9 @@ fn encode_info_for_item(ecx: &EncodeContext,
             }
         }
 
+        // Encode inherent implementations for this structure.
+        encode_inherent_implementations(ecx, ebml_w, def_id);
+
         /* Each class has its own index -- encode it */
         let bkts = create_index(idx);
         encode_index(ebml_w, bkts, write_i64);
@@ -1069,6 +1108,10 @@ fn encode_info_for_item(ecx: &EncodeContext,
             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);
         }
+
+        // Encode the implementations of this trait.
+        encode_extension_implementations(ecx, ebml_w, def_id);
+
         ebml_w.end_tag();
 
         // Now output the method info for each method.
@@ -1130,6 +1173,9 @@ fn encode_info_for_item(ecx: &EncodeContext,
 
             ebml_w.end_tag();
         }
+
+        // Encode inherent implementations for this trait.
+        encode_inherent_implementations(ecx, ebml_w, def_id);
       }
       item_mac(*) => fail!("item macros unimplemented")
     }
@@ -1523,17 +1569,36 @@ struct ImplVisitor<'self> {
 impl<'self> Visitor<()> for ImplVisitor<'self> {
     fn visit_item(&mut self, item: @item, _: ()) {
         match item.node {
-            item_impl(*) => {
-                self.ebml_w.start_tag(tag_impls_impl);
-                encode_def_id(self.ebml_w, local_def(item.id));
-                self.ebml_w.end_tag();
+            item_impl(_, Some(ref trait_ref), _, _) => {
+                let def_map = self.ecx.tcx.def_map;
+                let trait_def = def_map.get_copy(&trait_ref.ref_id);
+                let def_id = ast_util::def_id_of_def(trait_def);
+
+                // Load eagerly if this is an implementation of the Drop trait
+                // or if the trait is not defined in this crate.
+                if def_id == self.ecx.tcx.lang_items.drop_trait().unwrap() ||
+                        def_id.crate != LOCAL_CRATE {
+                    self.ebml_w.start_tag(tag_impls_impl);
+                    encode_def_id(self.ebml_w, local_def(item.id));
+                    self.ebml_w.end_tag();
+                }
             }
             _ => {}
         }
         visit::walk_item(self, item, ());
     }
 }
 
+/// Encodes implementations that are eagerly loaded.
+///
+/// None of this is necessary in theory; we can load all implementations
+/// lazily. However, in two cases the optimizations to lazily load
+/// implementations are not yet implemented. These two cases, which require us
+/// to load implementations eagerly, are:
+///
+/// * Destructors (implementations of the Drop trait).
+///
+/// * Implementations of traits not defined in this crate.
 fn encode_impls(ecx: &EncodeContext,
                 crate: &Crate,
                 ebml_w: &mut writer::Encoder) {

src/librustc/middle/privacy.rs

@@ -225,7 +225,7 @@ impl PrivacyVisitor {
 
         if method_id.crate == LOCAL_CRATE {
             let is_private = self.method_is_private(span, method_id.node);
-            let container_id = ty::method(self.tcx, method_id).container_id;
+            let container_id = ty::method(self.tcx, method_id).container_id();
             if is_private &&
                     (container_id.crate != LOCAL_CRATE ||
                      !self.privileged_items.iter().any(|x| x == &(container_id.node))) {

src/librustc/middle/trans/callee.rs

@@ -283,6 +283,14 @@ pub fn trans_fn_ref_with_vtables(
                               self_ty: None,
                               tps: /*bad*/ type_params.to_owned() };
 
+    // Load the info for the appropriate trait if necessary.
+    match ty::trait_of_method(tcx, def_id) {
+        None => {}
+        Some(trait_id) => {
+            ty::populate_implementations_for_trait_if_necessary(tcx, trait_id)
+        }
+    }
+
     // We need to do a bunch of special handling for default methods.
     // We need to modify the def_id and our substs in order to monomorphize
     // the function.
@@ -303,7 +311,7 @@ pub fn trans_fn_ref_with_vtables(
             // So, what we need to do is find this substitution and
             // compose it with the one we already have.
 
-            let impl_id = ty::method(tcx, def_id).container_id;
+            let impl_id = ty::method(tcx, def_id).container_id();
             let method = ty::method(tcx, source_id);
             let trait_ref = ty::impl_trait_ref(tcx, impl_id)
                 .expect("could not find trait_ref for impl with \

src/librustc/middle/trans/meth.rs

@@ -176,6 +176,10 @@ pub fn trans_method_callee(bcx: @mut Block,
         }) => {
             match bcx.fcx.param_substs {
                 Some(substs) => {
+                    ty::populate_implementations_for_trait_if_necessary(
+                        bcx.tcx(),
+                        trait_id);
+
                     let vtbl = find_vtable(bcx.tcx(), substs,
                                            p, b);
                     trans_monomorphized_callee(bcx, callee_id, this, mentry,
@@ -210,6 +214,8 @@ pub fn trans_static_method_callee(bcx: @mut Block,
            callee_id);
     let _indenter = indenter();
 
+    ty::populate_implementations_for_trait_if_necessary(bcx.tcx(), trait_id);
+
     // When we translate a static fn defined in a trait like:
     //
     //   trait<T1...Tn> Trait {
@@ -575,6 +581,8 @@ fn emit_vtable_methods(bcx: @mut Block,
                                     make a vtable for a type impl!")
     };
 
+    ty::populate_implementations_for_trait_if_necessary(bcx.tcx(), trt_id);
+
     let trait_method_def_ids = ty::trait_method_def_ids(tcx, trt_id);
     do trait_method_def_ids.map |method_def_id| {
         let ident = ty::method(tcx, *method_def_id).ident;