Allow passing self as an argument to methods

Part of UFCS (#16293)

src/librustc/middle/resolve.rs

@@ -5751,22 +5751,6 @@ impl<'a> Resolver<'a> {
                         // Write the result into the def map.
                         debug!("(resolving expr) resolved `{}`",
                                self.path_idents_to_string(path));
-
-                        // First-class methods are not supported yet; error
-                        // out here.
-                        match def {
-                            (DefMethod(..), _) => {
-                                self.resolve_error(expr.span,
-                                                      "first-class methods \
-                                                       are not supported");
-                                self.session.span_note(expr.span,
-                                                       "call the method \
-                                                        using the `.` \
-                                                        syntax");
-                            }
-                            _ => {}
-                        }
-
                         self.record_def(expr.id, def);
                     }
                     None => {

src/librustc/middle/trans/callee.rs

@@ -165,7 +165,7 @@ fn trans<'blk, 'tcx>(bcx: Block<'blk, 'tcx>, expr: &ast::Expr)
                 let def_id = inline::maybe_instantiate_inline(bcx.ccx(), did);
                 Callee { bcx: bcx, data: Intrinsic(def_id.node, substs) }
             }
-            def::DefFn(did, _, _) |
+            def::DefFn(did, _, _) | def::DefMethod(did, _) |
             def::DefStaticMethod(did, def::FromImpl(_), _) => {
                 fn_callee(bcx, trans_fn_ref(bcx, did, ExprId(ref_expr.id)))
             }
@@ -205,7 +205,7 @@ fn trans<'blk, 'tcx>(bcx: Block<'blk, 'tcx>, expr: &ast::Expr)
             def::DefTy(..) | def::DefPrimTy(..) | def::DefAssociatedTy(..) |
             def::DefUse(..) | def::DefTyParamBinder(..) |
             def::DefRegion(..) | def::DefLabel(..) | def::DefTyParam(..) |
-            def::DefSelfTy(..) | def::DefMethod(..) => {
+            def::DefSelfTy(..) => {
                 bcx.tcx().sess.span_bug(
                     ref_expr.span,
                     format!("cannot translate def {:?} \

src/librustc/middle/typeck/check/mod.rs

@@ -5029,7 +5029,8 @@ pub fn polytype_for_def(fcx: &FnCtxt,
       }
       def::DefFn(id, _, _) | def::DefStaticMethod(id, _, _) |
       def::DefStatic(id, _) | def::DefVariant(_, id, _) |
-      def::DefStruct(id) | def::DefConst(id) => {
+      def::DefStruct(id) | def::DefConst(id) |
+      def::DefMethod(id, _) => {
         return ty::lookup_item_type(fcx.ccx.tcx, id);
       }
       def::DefTrait(_) |
@@ -5057,9 +5058,6 @@ pub fn polytype_for_def(fcx: &FnCtxt,
       def::DefSelfTy(..) => {
         fcx.ccx.tcx.sess.span_bug(sp, "expected value, found self ty");
       }
-      def::DefMethod(..) => {
-        fcx.ccx.tcx.sess.span_bug(sp, "expected value, found method");
-      }
     }
 }