if gover.IsToolchain(path) {
			continue
		}
		old := r.initialVersion[path]
		new := reason.version
		if old != new && (old != "" || new != "none") {
			changes[path] = change{path, old, new}
		}
	}

	// Collect changes to explicit requirements in go.mod.
	for _, req := range oldReqs {
		if gover.IsToolchain(req.Path) {
			continue
		}