Fix an ICE when dereferencing types which cannot be dereferenced

Author: alexcrichton

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

@@ -413,12 +413,9 @@ fn constrain_derefs(rcx: @mut Rcx,
 
         match ty::deref(tcx, derefd_ty, true) {
             Some(mt) => derefd_ty = mt.ty,
-            None => {
-                tcx.sess.span_bug(
-                    deref_expr.span,
-                    fmt!("%?'th deref is of a non-deref'able type `%s`",
-                         i, rcx.fcx.infcx().ty_to_str(derefd_ty)));
-            }
+            /* if this type can't be dereferenced, then there's already an error
+               in the session saying so. Just bail out for now */
+            None => break
         }
     }
 }

src/test/compile-fail/deref-non-pointer.rs

@@ -8,9 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// error-pattern:cannot be dereferenced
 fn main() {
-  match *1 {
+  match *1 { //~ ERROR: cannot be dereferenced
       _ => { fail!(); }
   }
 }