--noImplicitReturns

This ensures we return a value in all branches of a function if the return type isn't void.

Let's see this in action with an example:

1. In our OrderDetail class, let's say we have the following implementation for our getTotal method:

getTotal(discount: number): number {
  if (discount) {
    const priceWithoutDiscount = this.product.unitPrice * this.quantity;
    const discountAmount = priceWithoutDiscount * discount;
    return priceWithoutDiscount - discountAmount;
  } else {
    // We forgot about this branch!
  }
}

1. We've forgotten to implement the branch of code that deals with the case where there is no discount. If we compile the code without the --noImplicitReturns flag, it compiles fine:

tsc orderDetail

1. However, let's see what happens if we compile the code with the --noImplicitReturns flag:

tsc orderDetail --noImplicitReturns

We get the following error, as expected:

orderDetail.ts(9,31): error TS7030: Not all code paths return a value.