Revert "Suppress type error message involving a function type whose result is ty_err"

This reverts commit e45312e5a0.

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

@@ -741,14 +741,6 @@ fn type_error_message(sp: span, mk_msg: fn(~str) -> ~str,
         // Don't report an error if actual type is ty_err.
         match ty::get(actual_ty).sty {
             ty::ty_err => return,
-            // Should really not report an error if the type
-            // has ty_err anywhere as a component, but that's
-            // annoying since we haven't written a visitor for
-            // ty::t yet
-            ty::ty_fn(fty) => match ty::get(fty.sig.output).sty {
-                ty::ty_err => return,
-                _ => ()
-            },
             _           => ()
         }
         let error_str = err.map_default(~"", |t_err|