what are const scope parameters?

[Denton Cockburn]

On Sat, 08 Mar 2008 00:24:23 -0500, Denton Cockburn wrote:

> On Fri, 07 Mar 2008 23:19:02 -0500, Jason House wrote:
>> 
>> cast at your own risk ;)
>> Having c2 still alive in main after the call to bar is ok and expected.  The
>> idea is that bar can't keep it but gives no restrictions on the caller. 
>> The cast that breaks this stuff is your fault ;)
> 
> Ok, without casts.  The point is that the scope specification doesn't
> affect the variable at all from what I can see.
> 
> I'm thinking the two specifications are the same ("in X p" and "const(X) p")
> I need to see an example or an explanation of a situation in which it
> doesn't hold.  I wasn't able to find anything in the docs.

doh! Forgot to include the cast-free code:

import std.stdio;
 
 class C
 {
	int x;
 }
 
 
 // with in and const, neither function can change the parameter
 const(C) foo(in C c)
 {
	C d = new C;
	d.x = c.x;
	writefln("foo.d.x = ", d.x);
	
	return c;
 }
 
 const(C) bar(const C c)
 {
	C d = new C;
	d.x = c.x; // we've made use of c
	writefln("bar.d.x = ", d.x);
	
	return c;
 }
 
 void main()
 {
	C c = new C;
	c.x = 5;
	auto c2 = foo(c);
	auto c3 = bar(c2); // CLEARLY c2 is still alive here, so what has scope done?
	
	writefln(c3.x);
 }