interface User {
isActive: boolean;
deletedAt: Date;
lastLogin: Date;
}
function processUser(user: User) {
if (user.isActive && user.deletedAt) {
// ⚠ Contradiction: active AND deleted?
sendWelcomeEmail(user);
}
if (!user.isActive) {
user.lastLogin = new Date();
// ⚠ Dead path: updating inactive user
}
return user.isActive
? "active"
: user.deletedAt
? "deleted"
: "inactive";
}isActive === true with non-null deletedAt creates impossible state. Active users cannot be deleted.lastLogin update has no downstream consumers when isActive === false."inactive" unreachable: if !isActive and !deletedAt, the User type requires deletedAt: Date (non-optional).