Create a new channel as a copy of main.
Rename main to:
Delete main? This cannot be undone.
// RUN: %clang_cc1 %s -std=c2x -Wpre-c2x-compat -pedantic -fsyntax-only -verify int digit_seps = 123'456; // expected-warning {{digit separators are incompatible with C standards before C2x}}