Change syntax for impl

Move the name of the bundle to the front, allow type parameters (not
handled yet), and add a 'for' keyword:

    impl utils for int {
        fn str() -> str { int::str(self) }
        fn times(f: block()) { ... }
    }

src/comp/syntax/ast.rs

@@ -505,7 +505,7 @@ tag item_ {
              node_id /* dtor id */,
              [ty_param],
              node_id /* ctor id */);
-    item_impl(@path /* iface */, @ty /* self */, [@method]);
+    item_impl([ty_param], @ty /* self */, [@method]);
 }
 
 type native_item =

src/comp/syntax/fold.rs

@@ -235,8 +235,8 @@ fn noop_fold_item_underscore(i: item_, fld: ast_fold) -> item_ {
                       methods: vec::map(fld.fold_method, o.methods)},
                      typms, d)
           }
-          item_impl(iface, ty, methods) {
-            item_impl(fld.fold_path(iface), fld.fold_ty(ty),
+          item_impl(tps, ty, methods) {
+            item_impl(tps, fld.fold_ty(ty),
                       vec::map(fld.fold_method, methods))
           }
           item_res(dtor, did, typms, cid) {

src/comp/syntax/parse/parser.rs

@@ -1859,14 +1859,14 @@ fn parse_item_obj(p: parser, attrs: [ast::attribute]) -> @ast::item {
 }
 
 fn parse_item_impl(p: parser, attrs: [ast::attribute]) -> @ast::item {
-    let lo = p.get_last_lo_pos(), ty = parse_ty(p, false);
-    expect(p, token::COLON);
-    let path = parse_path(p), meths = [];
+    let lo = p.get_last_lo_pos(), ident = parse_ident(p),
+        tps = parse_ty_params(p);
+    expect_word(p, "for");
+    let ty = parse_ty(p, false), meths = [];
     expect(p, token::LBRACE);
     while !eat(p, token::RBRACE) { meths += [parse_method(p)]; }
-    ret mk_item(p, lo, p.get_last_hi_pos(),
-                path.node.idents[vec::len(path.node.idents) - 1u],
-                ast::item_impl(path, ty, meths), attrs);
+    ret mk_item(p, lo, p.get_last_hi_pos(), ident,
+                ast::item_impl(tps, ty, meths), attrs);
 }
 
 fn parse_item_res(p: parser, attrs: [ast::attribute]) -> @ast::item {

src/comp/syntax/print/pprust.rs

@@ -347,12 +347,6 @@ fn print_native_item(s: ps, item: @ast::native_item) {
         end(s); // end the outer ibox
 
       }
-
-
-
-
-
-
       ast::native_item_fn(decl, typarams) {
         print_fn(s, decl, ast::proto_bare, item.ident, typarams,
                  decl.constraints);
@@ -483,11 +477,14 @@ fn print_item(s: ps, &&item: @ast::item) {
         }
         bclose(s, item.span);
       }
-      ast::item_impl(path, ty, methods) {
+      ast::item_impl(tps, ty, methods) {
         head(s, "impl");
+        word(s.s, item.ident);
+        print_type_params(s, tps);
+        nbsp(s);
+        word_nbsp(s, "for");
         print_type(s, ty);
-        word_space(s, ":");
-        print_path(s, path, false);
+        space(s.s);
         bopen(s);
         for meth in methods {
             hardbreak_if_not_bol(s);

src/comp/syntax/visit.rs

@@ -105,8 +105,7 @@ fn visit_item<E>(i: @item, e: E, v: vt<E>) {
                        e, v);
         }
       }
-      item_impl(path, ty, methods) {
-        visit_path(path, e, v);
+      item_impl(_, ty, methods) {
         visit_ty(ty, e, v);
         for m in methods {
             v.visit_fn(m.node.meth, [], m.span, some(m.node.ident), m.node.id,

src/test/run-pass/static-impl.rs

@@ -0,0 +1,18 @@
+import a::*;
+import b::baz;
+
+mod a {
+    impl foo for uint { fn plus() -> int { self as int + 20 } }
+}
+
+mod b {
+    impl baz for str { fn plus() -> int { 200 } }
+}
+
+fn main() {
+    impl foo for int { fn plus() -> int { self + 10 } }
+    assert 10.plus() == 20;
+    assert 10u.plus() == 30;
+    assert "hi".plus() == 200;
+}
+