compiler: Don't allow shifts with non-integers.

    
    Fixes golang/go#11616.
    
    Reviewed-on: https://go-review.googlesource.com/13688

From-SVN: r227604

gcc/go/gofrontend/MERGE

-672ac2abc52d8bd70cb9fb03dd4a32fdde9c438f
+913b47c957ea91db2f724491d88cb20e8f9be8c7
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.

gcc/go/gofrontend/expressions.cc

@@ -4523,6 +4523,12 @@ Binary_expression::eval_constant(Operator op, Numeric_constant* left_nc,
     return false;
   if (!is_shift && !right_nc->set_type(type, true, location))
     return false;
+  if (is_shift
+      && ((left_type->integer_type() == NULL
+           && !left_type->is_abstract())
+          || (right_type->integer_type() == NULL
+              && !right_type->is_abstract())))
+    return false;
 
   bool r;
   if (type->complex_type() != NULL)