This test checks the fix for golang/go#64547: the lostcancel analyzer reports
diagnostics that overflow the file.

-- p.go --
package p

import "context"

func _() {
	_, cancel := context.WithCancel(context.Background()) //@diag("_, cancel", re"not used on all paths")
	if false {
		cancel()
	}
} //@diag("}", re"may be reached without using the cancel")