vhdlpp: Corrected an error message.

vhdlpp/expression_evaluate.cc

@@ -147,12 +147,13 @@ bool ExpName::evaluate(Entity*ent, ScopeBase*scope, int64_t&val) const
       if (ent) {
           const InterfacePort*gen = ent->find_generic(name_);
           if (gen) {
-              cerr << get_fileline() << ": sorry: I don't necessarily "
-                   << "handle generic overrides." << endl;
-
               // Evaluate the default expression and use that.
-              if (gen->expr)
-                  return gen->expr->evaluate(ent, scope, val);
+              if (gen->expr && gen->expr->evaluate(ent, scope, val))
+                  return true;
+
+              cerr << get_fileline() << ": sorry: I could not evaluate "
+                   << "generic override." << endl;
+              return false;
           }
       }