'Property does not exist on type 'never'

I had the same error and replaced the dot notation with bracket notation to suppress it.

e.g.:

obj.name -> obj['name']

Because you are assigning instance to null. The compiler infers that it can never be anything other than null. So it assumes that the else block should never be executed so instance is typed as never in the else block.

Now if you don't declare it as the literal value null, and get it by any other means (ex: let instance: Foo | null = getFoo();), you will see that instance will be null inside the if block and Foo inside the else block.

Never type documentation: https://www.typescriptlang.org/docs/handbook/basic-types.html#never

Edit:

The issue in the updated example is actually an open issue with the compiler. See:

https://github.com/Microsoft/TypeScript/issues/11498 https://github.com/Microsoft/TypeScript/issues/12176

if you write Component as React.FC, and using useState(),

just write like this would be helpful:

const [arr, setArr] = useState<any[]>([])