Shadowing a parameter

From: Aguilar, James (jfa1_at_cec.NOBOTSwustl.edu)
Date: 08/08/04 

Date: Sun, 8 Aug 2004 16:52:04 -0400

Hey all. I was making a newbie mistake that I eventually figured out. That
is not my question. My question is about the error message. So let me set
the stage for you:

class Superclass
{
public:
  Superclass(int);
}

class Subclass : public Superclass
{
public:
  Subclass(int);
}

As you all surely know, the way to declare the constructor of subclass so
that it uses that of superclass is

Subclass::Subclass(int x)
  : Superclass(x)
{ . . . }

As a newbie who comes from a Java background, I somehow managed to miss this
colon initializer notation in my text (B.Stoustrup or however you spell it).
So I was writing it as any Java newbie would:

Subclass::Subclass(int x)
{ Superclass::Superclass(x); . . . }

The real question, though, is why the heck can't the error message be more
useful:

"Error: declaration of x shadows parameter"

What in the world does that mean? What is "shadowing" a parameter. And
where do I declare something that does so? As far as I can see, the
parameter itself is the only declaration of any kind. This is from g++ for
Cygwin, whatever the most recent version is.

Yours,

James

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