Proper disposing of class implementing IDisposable

Which one of the below 2 code pieces is not calling dispose and therefore is bad practice:

...
using(SomeIDisposable p = new SomeIDisposable())
{
  return p.Get开发者_如何学CSomething(...);
}
...

or

...
return new SomeIDisposable().GetSomething(...);    
...

?

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Number two does not call dispose.