Disallow overloading a method with one of different type. Closes #703.

Author: lkuper

src/comp/middle/trans.rs

@@ -6777,11 +6777,6 @@ fn create_vtbl(cx: @local_ctxt, sp: &span, outer_obj_ty: ty::t,
                 // member of addtl_meths.  Instead, we have to go
                 // through addtl_meths and see if there's some method
                 // in it that has the same name as fm.
-
-                // FIXME (part of #543): We're only checking names
-                // here.  If a method is replacing another, it also
-                // needs to have the same type, but this should
-                // probably be enforced in typechecking.
                 for am: @ast::method  in addtl_meths {
                     if str::eq(am.node.ident, fm.ident) { ret none; }
                 }

src/comp/middle/typeck.rs

@@ -2427,19 +2427,29 @@ fn check_expr(fcx: &@fn_ctxt, expr: &@ast::expr) -> bool {
             // Whenever an outer method overrides an inner, we need to remove
             // that inner from the type.  Filter inner_obj_methods to remove
             // any methods that share a name with an outer method.
-            fn filtering_fn(m: &ty::method,
+            fn filtering_fn(ccx: @crate_ctxt,
+                            m: &ty::method,
                             outer_obj_methods: (@ast::method)[]) ->
                 option::t[ty::method] {
 
                 for om: @ast::method in outer_obj_methods {
                     if str::eq(om.node.ident, m.ident) {
+                        // We'd better be overriding with one of the same
+                        // type.  Check to make sure.
+                        let new_type = ty_of_method(ccx, om);
+                        if new_type != m {
+                            ccx.tcx.sess.span_fatal(
+                                om.span,
+                                "Attempted to override method " +
+                                m.ident + " with one of a different type");
+                        }
                         ret none;
                     }
                 }
                 ret some(m);
             }
 
-            let f = bind filtering_fn(_, ao.methods);
+            let f = bind filtering_fn(fcx.ccx, _, ao.methods);
             inner_obj_methods =
                 std::ivec::filter_map[ty::method,
                                       ty::method](f, inner_obj_methods);

src/test/compile-fail/anon-obj-overloading-wrong-type.rs renamed to src/test/compile-fail/anon-obj-overriding-wrong-type.rs

@@ -1,7 +1,4 @@
-//xfail-stage0
-//xfail-stage1
-//xfail-stage2
-//xfail-stage3
+//error-pattern: with one of a different type
 use std;
 
 fn main() {
@@ -13,8 +10,7 @@ fn main() {
 
     let my_a = a();
 
-    // This compiles and shouldn't.  You should only be able to
-    // overload a method with one of the same type.  Issue #703.
+    // Attempting to override a method with one of a different type.
     let my_b =
         obj () {
             fn foo() -> str { ret "hello"; }
@@ -23,4 +19,4 @@ fn main() {
         };
 
     log_err my_b.foo();
-}
+}