Why should variable shadowing be allowed?

Question

Today I came across a term I had not heard of before: variable shadowing.The general opinion about variable shadowing is that it is frowned upon for code readability and comprehension.What would be a use case for programming languages to allow variable shadowing?

PaulHoule · Accepted Answer

In java I like using variable shadowing in constructors, that is, I write something like:

  public SomeObject(String aField) {
    this.aField = aField;
  }

I think this promotes clarity for the user of the code, although you can possibly make the mistake of writing

  aField = aField;

but if you declare aField as final, the compiler will give you an error if you make that mistake.