Several small changes. Mostly reformatting, adding parens.

Check for free in class and method only if nested scopes are enabled.

Add assertion to verify that no free variables occur when nested
scopes are disabled.

XXX When should nested scopes by made non-optional on the trunk?

Python/compile.c

@@ -4078,7 +4078,7 @@ symtable_resolve_free(struct compiling *c, PyObject *name, int flags,
 		   anything here.
 		*/
 		if (is_free(flags ^ DEF_FREE_CLASS) 
-		    || flags == DEF_FREE_CLASS)
+		    || (flags == DEF_FREE_CLASS))
 			return 0;
 		v = PyInt_FromLong(si->si_nfrees++);
 		dict = c->c_freevars;
@@ -4260,6 +4260,7 @@ symtable_check_shadow(struct symtable *st, PyObject *name, int flags)
 
 	if (!(flags & DEF_BOUND))
 		return 0;
+
 	/* The semantics of this code will change with nested scopes.
 	   It is defined in the current scope and referenced in a
 	   child scope.  Under the old rules, the child will see a
@@ -4364,8 +4365,10 @@ symtable_load_symbols(struct compiling *c)
 		   2. Free variables in methods that are also class
 		   variables or declared global.
 		*/
-		if (flags & (DEF_FREE | DEF_FREE_CLASS)) {
+		if (st->st_nested_scopes) {
+		    if (flags & (DEF_FREE | DEF_FREE_CLASS)) {
 			symtable_resolve_free(c, name, flags, &si);
+		    }
 		}
 
 		if (flags & DEF_STAR) {
@@ -4425,15 +4428,11 @@ symtable_load_symbols(struct compiling *c)
 		}
 	}
 
-	/*
-	fprintf(stderr, 
-		"cells %d: %s\n"
-		"frees %d: %s\n",
-		si.si_ncells, PyObject_REPR(c->c_cellvars),
-		si.si_nfrees, PyObject_REPR(c->c_freevars));
-	*/
 	assert(PyDict_Size(c->c_freevars) == si.si_nfrees);
 
+	if (st->st_nested_scopes == 0)
+		assert(si.si_nfrees == 0);
+
 	if (si.si_ncells > 1) { /* one cell is always in order */
 		if (symtable_cellvar_offsets(&c->c_cellvars, c->c_argcount,
 					     c->c_varnames, c->c_flags) < 0)
@@ -4538,7 +4537,9 @@ symtable_update_free_vars(struct symtable *st)
 			   referenced in scope B contained (perhaps
 			   indirectly) in A and there are no scopes
 			   with bindings for N between B and A, then N
-			   is global in B.
+			   is global in B.  Unless A is a class scope,
+			   because class scopes are not considered for
+			   nested scopes.
 			*/
 			if (v && (ste->ste_type != TYPE_CLASS)) {
 				int flags = PyInt_AS_LONG(v);