--noImplicitAny

This forces us to explicitly specify the any type where we want to use it. This forces us to think about our use of any and whether we really need it.

Let's explore this with an example:

1. Let's add a doSomething method to our OrderDetail class that has a parameter called input with no type annotation:

export class OrderDetail {
  ...
  doSomething(input) {
    input.something();
    return input.result;
  }
}

1. Let's do a compilation with the --noImplicitAny flag in the Terminal:

tsc orderDetail --noImplicitAny

The compiler outputs the following error message because we haven't explicitly said what type the input parameter is:

orderDetail.ts(14,15): error TS7006: Parameter 'input' implicitly has an 'any' type.

1. We can fix this by adding a type annotation with any or, better still, something more specific:

doSomething(input: {something: () => void, result: string}) {
  input.something();
  return input.result;
}

If we do a compilation with --noImplicitAny again, the compiler is happy.