http://d.puremagic.com/issues/show_bug.cgi?id=7482

           Summary: deprecation isn't checked inside forward referenced
                    is(typeof())
           Product: D
           Version: D1 & D2
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: nobody@puremagic.com
        ReportedBy: clugdbug@yahoo.com.au


--- Comment #0 from Don <clugdbug@yahoo.com.au> 2012-02-10 22:12:36 PST ---
static if (is(typeof(Z))) {} else {static assert(0, "first time");}

deprecated int Z;

static if (is(typeof(Z))) {} else {static assert(0, "second time lucky");}
----------
crash.d(5): Error: static assert  "second time lucky"
It should assert the first time.

This is another gagging bug, related to bug 4269, but the problem isn't an invalid type. Here, the first typeof doesn't check deprecation.

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Stewart Gordon <smjg@iname.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |spec
                 CC|                            |smjg@iname.com
             Blocks|                            |340


--- Comment #1 from Stewart Gordon <smjg@iname.com> 2012-02-11 16:21:47 PST ---
I'm not sure what's meant to happen here.  Z still exists, even if it's deprecated.  But by deprecating it, we are basically telling the compiler to treat it as if it doesn't exist.

This is a difficult case, because to treat deprecated stuff as nonexistent in IsExpressions causes the program to compile and behave differently depending on whether the compiler switch to enable deprecated features is switched on or not.

If the correct behaviour is given anywhere in the spec, I haven't managed to find it.

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Walter Bright <bugzilla@digitalmars.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |bugzilla@digitalmars.com


--- Comment #2 from Walter Bright <bugzilla@digitalmars.com> 2012-02-12 11:25:33 PST ---
Deprecation is most definitely not about declarations not existing. It is about being an error to reference them.

For example,

   deprecated void foo(int);
   void foo(long);

   ...
   foo(0);   // error, foo(int) is deprecated

rather than selecting foo(long), which it would if foo(int) "disappeared".

IOW, deprecation checking is done *after* symbol resolution, not before.

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timon.gehr@gmx.ch changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |timon.gehr@gmx.ch


--- Comment #3 from timon.gehr@gmx.ch 2012-02-12 11:36:25 PST ---
I think both static if conditions should fail to compile because they reference a deprecated symbol. In other words, error gagging should not apply to deprecation errors. It should be impossible for 'deprecated' to silently change the behavior of a program.

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--- Comment #4 from Stewart Gordon <smjg@iname.com> 2012-02-12 12:46:45 PST ---
I've started a thread on the newsgroup about this whole topic.
"Thoughts about deprecation"
http://tinyurl.com/832hhqj

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Don <clugdbug@yahoo.com.au> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|deprecation isn't checked   |deprecation isn't checked
                   |inside forward referenced   |inside forward referenced
                   |is(typeof())                |typeof()


--- Comment #5 from Don <clugdbug@yahoo.com.au> 2012-02-16 12:28:46 PST ---
> Deprecation is most definitely not about declarations not existing. It is about being an error to reference them.
Right, but is(typeof(X)) isn't a check if X exists, even though a popular idiom
is to use it for that purpose. Rather, it asks what type X has. And I think
that has to be considered as referencing X, and is therefore an error.
If it's not an error, it has to be able to provide a type, and that's a
problem:

static if (is(typeof(Z)  M)) {
    M we_are_relying_on_a_deprecated_variable;
}

deprecated int Z;

But it turns out that this bug has nothing to do with is().

alias typeof(Z) Q1; // compiles

deprecated int Z;

alias typeof(Z) Q2; // doesn't compile


In fact, it seems it doesn't even require deprecated:

alias typeof(Z1) Q1;
pragma(msg, Q1.stringof); // int

const int Z1;

alias typeof(Z1) R1;
pragma(msg, R1.stringof); // const(int)

and yet if you write const (int) Z1; it displays const(int) in both cases.

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