Front-end support for default impls in traits.

src/libsyntax/ast.rs

@@ -452,6 +452,15 @@ type ty_field = spanned<ty_field_>;
 type ty_method = {ident: ident, attrs: ~[attribute],
                   decl: fn_decl, tps: ~[ty_param], span: span};
 
+#[auto_serialize]
+// A trait method is either required (meaning it doesn't have an
+// implementation, just a signature) or provided (meaning it has a default
+// implementation).
+enum trait_method {
+    required(ty_method),
+    provided(@method),
+}
+
 #[auto_serialize]
 enum int_ty { ty_i, ty_char, ty_i8, ty_i16, ty_i32, ty_i64, }
 
@@ -695,7 +704,7 @@ enum item_ {
                /* dtor is optional */
                option<class_dtor>
                ),
-    item_trait(~[ty_param], ~[ty_method]),
+    item_trait(~[ty_param], ~[trait_method]),
     item_impl(~[ty_param], option<@trait_ref> /* trait */,
               @ty /* self */, ~[@method]),
     item_mac(mac),

src/libsyntax/ast_util.rs

@@ -511,6 +511,9 @@ fn id_visitor(vfn: fn@(node_id)) -> visit::vt<()> {
         visit_ty_method: fn@(_ty_m: ty_method) {
         },
 
+        visit_trait_method: fn@(_ty_m: trait_method) {
+        },
+
         visit_class_item: fn@(c: @class_member) {
             alt c.node {
               instance_var(_, _, _, id,_) {

src/libsyntax/parse/parser.rs

@@ -42,14 +42,14 @@ import ast::{_mod, add, alt_check, alt_exhaustive, arg, arm, attribute,
              mtc_rep, mtc_tok, mul, mutability, neg, noreturn, not, pat,
              pat_box, pat_enum, pat_ident, pat_lit, pat_range, pat_rec,
              pat_tup, pat_uniq, pat_wild, path, private, proto, proto_any,
-             proto_bare, proto_block, proto_box, proto_uniq, public, pure_fn,
-             purity, re_anon, re_named, region, rem, ret_style,
-             return_val, shl, shr, stmt, stmt_decl,
-             stmt_expr, stmt_semi, subtract, token_tree, trait_ref, tt_delim,
-             tt_dotdotdot, tt_flat, tt_interpolate, ty, ty_, ty_bot, ty_box,
-             ty_constr, ty_constr_, ty_constr_arg, ty_field, ty_fn, ty_infer,
-             ty_mac, ty_method, ty_nil, ty_param, ty_path, ty_ptr, ty_rec,
-             ty_rptr, ty_tup, ty_u32, ty_uniq, ty_vec, ty_vstore,
+             proto_bare, proto_block, proto_box, proto_uniq, provided, public,
+             pure_fn, purity, re_anon, re_named, region, rem, required,
+             ret_style, return_val, shl, shr, stmt, stmt_decl, stmt_expr,
+             stmt_semi, subtract, token_tree, trait_method, trait_ref,
+             tt_delim, tt_dotdotdot, tt_flat, tt_interpolate, ty, ty_, ty_bot,
+             ty_box, ty_constr, ty_constr_, ty_constr_arg, ty_field, ty_fn,
+             ty_infer, ty_mac, ty_method, ty_nil, ty_param, ty_path, ty_ptr,
+             ty_rec, ty_rptr, ty_tup, ty_u32, ty_uniq, ty_vec, ty_vstore,
              unchecked_blk, uniq, unsafe_blk, unsafe_fn, variant, view_item,
              view_item_, view_item_export, view_item_import, view_item_use,
              view_path, view_path_glob, view_path_list, view_path_simple,
@@ -275,7 +275,7 @@ class parser {
              constraints: constrs};
     }
 
-    fn parse_ty_methods() -> ~[ty_method] {
+    fn parse_trait_methods() -> ~[trait_method] {
         do self.parse_unspanned_seq(token::LBRACE, token::RBRACE,
                                     seq_sep_none()) |p| {
             let attrs = p.parse_outer_attributes();
@@ -284,12 +284,42 @@ class parser {
             let ident = p.parse_method_name();
             let tps = p.parse_ty_params();
             let d = p.parse_ty_fn_decl(pur), fhi = p.last_span.hi;
-            self.expect(token::SEMI);
-            {ident: ident, attrs: attrs, decl: {purity: pur with d}, tps: tps,
-             span: mk_sp(flo, fhi)}
+            #debug["parse_trait_methods(): trait method ends in %s",
+                   token_to_str(self.reader, self.token)];
+            alt self.token {
+              token::SEMI {
+                self.bump();
+                required({ident: ident, attrs: attrs,
+                          decl: {purity: pur with d}, tps: tps,
+                          span: mk_sp(flo, fhi)})
+              }
+              token::LBRACE {
+                self.bump();
+                let (inner_attrs, body) =
+                    self.parse_inner_attrs_and_block(true);
+                let attrs = vec::append(attrs, inner_attrs);
+                self.eat(token::RBRACE);
+                provided(@{ident: ident,
+                           attrs: attrs,
+                           tps: tps,
+                           decl: d,
+                           body: body,
+                           id: self.get_id(),
+                           span: mk_sp(flo, fhi),
+                           self_id: self.get_id(),
+                           // Provided traits methods always public for now
+                           vis: public})
+              }
+
+              _ { self.fatal("expected ';' or '}` \
+                              but found `"
+                             + token_to_str(self.reader, self.token) + "`");
+                }
+            }
         }
     }
 
+
     fn parse_mt() -> mt {
         let mutbl = self.parse_mutability();
         let t = self.parse_ty(false);
@@ -2127,7 +2157,7 @@ class parser {
         let ident = self.parse_ident();
         self.parse_region_param();
         let tps = self.parse_ty_params();
-        let meths = self.parse_ty_methods();
+        let meths = self.parse_trait_methods();
         (ident, item_trait(tps, meths), none)
     }
 

src/libsyntax/print/pprust.rs

@@ -5,6 +5,7 @@ import pp::{break_offset, word, printer,
             space, zerobreak, hardbreak, breaks, consistent,
             inconsistent, eof};
 import diagnostic;
+import ast::{required, provided};
 import ast_util::operator_prec;
 import dvec::{dvec, extensions};
 import parse::classify::*;
@@ -593,7 +594,7 @@ fn print_item(s: ps, &&item: @ast::item) {
         print_type_params(s, tps);
         word(s.s, " ");
         bopen(s);
-        for methods.each |meth| { print_ty_method(s, meth); }
+        for methods.each |meth| { print_trait_method(s, meth); }
         bclose(s, item.span);
       }
       ast::item_mac({node: ast::mac_invoc_tt(pth, tts), _}) {
@@ -647,6 +648,13 @@ fn print_ty_method(s: ps, m: ast::ty_method) {
     word(s.s, ";");
 }
 
+fn print_trait_method(s: ps, m: ast::trait_method) {
+    alt m {
+      required(ty_m) { print_ty_method(s, ty_m) }
+      provided(m)    { print_method(s, m) }
+    }
+}
+
 fn print_method(s: ps, meth: @ast::method) {
     hardbreak_if_not_bol(s);
     maybe_print_comment(s, meth.span.lo);

src/libsyntax/visit.rs

@@ -62,6 +62,7 @@ type visitor<E> =
       visit_constr: fn@(@path, span, node_id, E, vt<E>),
       visit_fn: fn@(fn_kind, fn_decl, blk, span, node_id, E, vt<E>),
       visit_ty_method: fn@(ty_method, E, vt<E>),
+      visit_trait_method: fn@(trait_method, E, vt<E>),
       visit_class_item: fn@(@class_member, E, vt<E>)};
 
 fn default_visitor<E>() -> visitor<E> {
@@ -81,6 +82,7 @@ fn default_visitor<E>() -> visitor<E> {
           visit_constr: |a,b,c,d,e|visit_constr::<E>(a, b, c, d, e),
           visit_fn: |a,b,c,d,e,f,g|visit_fn::<E>(a, b, c, d, e, f, g),
           visit_ty_method: |a,b,c|visit_ty_method::<E>(a, b, c),
+          visit_trait_method: |a,b,c|visit_trait_method::<E>(a, b, c),
           visit_class_item: |a,b,c|visit_class_item::<E>(a, b, c)};
 }
 
@@ -160,7 +162,7 @@ fn visit_item<E>(i: @item, e: E, v: vt<E>) {
       item_trait(tps, methods) {
         v.visit_ty_params(tps, e, v);
         for methods.each |m| {
-            v.visit_ty_method(m, e, v);
+            v.visit_trait_method(m, e, v);
         }
       }
       item_mac(m) { visit_mac(m, e, v) }
@@ -317,6 +319,17 @@ fn visit_ty_method<E>(m: ty_method, e: E, v: vt<E>) {
     v.visit_ty(m.decl.output, e, v);
 }
 
+fn visit_trait_method<E>(m: trait_method, e: E, v: vt<E>) {
+    alt m {
+      required(ty_m) {
+        v.visit_ty_method(ty_m, e, v)
+      }
+      provided(m) {
+        visit_method_helper(m, e, v)
+      }
+    }
+}
+
 fn visit_block<E>(b: ast::blk, e: E, v: vt<E>) {
     for b.node.view_items.each |vi| { v.visit_view_item(vi, e, v); }
     for b.node.stmts.each |s| { v.visit_stmt(s, e, v); }
@@ -465,6 +478,7 @@ type simple_visitor =
       visit_constr: fn@(@path, span, node_id),
       visit_fn: fn@(fn_kind, fn_decl, blk, span, node_id),
       visit_ty_method: fn@(ty_method),
+      visit_trait_method: fn@(trait_method),
       visit_class_item: fn@(@class_member)};
 
 fn simple_ignore_ty(_t: @ty) {}
@@ -487,6 +501,7 @@ fn default_simple_visitor() -> simple_visitor {
           visit_fn: fn@(_fk: fn_kind, _d: fn_decl, _b: blk, _sp: span,
                         _id: node_id) { },
           visit_ty_method: fn@(_m: ty_method) { },
+          visit_trait_method: fn@(_m: trait_method) { },
           visit_class_item: fn@(_c: @class_member) {}
          };
 }
@@ -546,6 +561,11 @@ fn mk_simple_visitor(v: simple_visitor) -> vt<()> {
         f(ty);
         visit_ty_method(ty, e, v);
     }
+    fn v_trait_method(f: fn@(trait_method), m: trait_method, &&e: (),
+                      v: vt<()>) {
+        f(m);
+        visit_trait_method(m, e, v);
+    }
     fn v_ty_params(f: fn@(~[ty_param]),
                    ps: ~[ty_param],
                    &&e: (), v: vt<()>) {
@@ -596,6 +616,8 @@ fn mk_simple_visitor(v: simple_visitor) -> vt<()> {
                     v_fn(v.visit_fn, a, b, c, d, e, f, g),
                 visit_ty_method: |a,b,c|
                     v_ty_method(v.visit_ty_method, a, b, c),
+                visit_trait_method: |a,b,c|
+                    v_trait_method(v.visit_trait_method, a, b, c),
                 visit_class_item: |a,b,c|
                     v_class_item(v.visit_class_item, a, b, c)
                });

src/rustc/metadata/encoder.rs

@@ -744,12 +744,21 @@ fn encode_info_for_item(ecx: @encode_ctxt, ebml_w: ebml::writer, item: @item,
         encode_name(ebml_w, item.ident);
         let mut i = 0u;
         for vec::each(*ty::trait_methods(tcx, local_def(item.id))) |mty| {
-            ebml_w.start_tag(tag_item_trait_method);
-            encode_name(ebml_w, mty.ident);
-            encode_type_param_bounds(ebml_w, ecx, ms[i].tps);
-            encode_type(ecx, ebml_w, ty::mk_fn(tcx, mty.fty));
-            encode_family(ebml_w, purity_fn_family(mty.purity));
-            ebml_w.end_tag();
+            alt ms[i] {
+              required(ty_m) {
+                ebml_w.start_tag(tag_item_trait_method);
+                encode_name(ebml_w, mty.ident);
+                encode_type_param_bounds(ebml_w, ecx, ty_m.tps);
+                encode_type(ecx, ebml_w, ty::mk_fn(tcx, mty.fty));
+                encode_family(ebml_w, purity_fn_family(mty.purity));
+                ebml_w.end_tag();
+              }
+              provided(m) {
+                encode_info_for_method(ecx, ebml_w, path,
+                                       should_inline(m.attrs), item.id,
+                                       m, m.tps);
+              }
+            }
             i += 1u;
         }
         encode_path(ebml_w, path, ast_map::path_name(item.ident));

src/rustc/middle/resolve.rs

@@ -1,6 +1,7 @@
 import syntax::{ast, ast_util, codemap, ast_map};
 import syntax::ast::*;
 import ast::{ident, fn_ident, def, def_id, node_id};
+import ast::{required, provided};
 import syntax::ast_util::{local_def, def_id_of_def, new_def_hash,
                           class_item_ident, path_to_ident};
 import pat_util::*;
@@ -566,12 +567,8 @@ fn visit_item_with_scope(e: @env, i: @ast::item,
       }
       ast::item_trait(tps, methods) {
         v.visit_ty_params(tps, sc, v);
-        let isc = @cons(scope_method(i.id, tps), sc);
         for methods.each |m| {
-            v.visit_ty_params(m.tps, isc, v);
-            let msc = @cons(scope_method(i.id, vec::append(tps, m.tps)), sc);
-            for m.decl.inputs.each |a| { v.visit_ty(a.ty, msc, v); }
-            v.visit_ty(m.decl.output, msc, v);
+            visit_trait_method(m, i, tps, sc, v);
         }
       }
       ast::item_class(tps, traits, members, ctor, m_dtor) {
@@ -618,6 +615,27 @@ fn visit_item_with_scope(e: @env, i: @ast::item,
     e.resolve_unexported = old_resolve_unexported;
 }
 
+fn visit_trait_method(m: trait_method, i: @ast::item,
+                      tps: ~[ast::ty_param], sc: scopes,
+                      v: vt<scopes>) {
+    alt m {
+      required(ty_m) {
+        let isc = @cons(scope_method(i.id, tps), sc);
+        v.visit_ty_params(ty_m.tps, isc, v);
+        let msc = @cons(scope_method(i.id, vec::append(tps, ty_m.tps)), sc);
+        for ty_m.decl.inputs.each |a| { v.visit_ty(a.ty, msc, v); }
+        v.visit_ty(ty_m.decl.output, msc, v);
+      }
+      provided(m) {
+         v.visit_ty_params(m.tps, sc, v);
+        let msc = @cons(scope_method(m.self_id, vec::append(tps, m.tps)),
+                        sc);
+        v.visit_fn(visit::fk_method(m.ident, ~[], m),
+                   m.decl, m.body, m.span, m.id, msc, v);
+      }
+    }
+}
+
 fn visit_foreign_item_with_scope(ni: @ast::foreign_item, &&sc: scopes,
                                 v: vt<scopes>) {
     visit::visit_foreign_item(ni, @cons(scope_foreign_item(ni), sc), v);
@@ -1785,7 +1803,16 @@ fn check_item(e: @env, i: @ast::item, &&x: (), v: vt<()>) {
                       "type parameter");
       }
       ast::item_trait(_, methods) {
-        ensure_unique(*e, i.span, methods, |m| m.ident,
+        ensure_unique(*e, i.span, methods, |m| {
+            alt m {
+              required(ty_m) {
+                ty_m.ident
+              }
+              provided(m) {
+                m.ident
+              }
+            }
+        },
                       "method");
       }
       ast::item_impl(_, _, _, methods) {