http://d.puremagic.com/issues/show_bug.cgi?id=5297

           Summary: The lookup order of recursive with statements is
                    undefined.
           Product: D
           Version: unspecified
          Platform: Other
        OS/Version: All
            Status: NEW
          Severity: trivial
          Priority: P2
         Component: websites
        AssignedTo: nobody@puremagic.com
        ReportedBy: blood.of.life@gmail.com


--- Comment #0 from Bernard Helyer <blood.of.life@gmail.com> 2010-12-01 05:27:29 PST ---
In implementing SDC I find myself asking these questions, and I wish to try and put and end to DMD being the sole definer of semantics; just letting you know the reason for this and subsequent bug reports.

Given a series of with statements:

    with (a) with (b) with (c) {
        d();
    }

If all three objects have a method d(), then c gets called. Obviously the with statements are considered in a LIFO order, and the sentence

http://www.digitalmars.com/d/2.0/statement.html#WithStatement
"Use of with object symbols that shadow local symbols with the same identifier
are not allowed. "

does not apply here. Neither is documented behaviour, and the only to figure out how D behaves is to run DMD.

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Simen Kjaeraas <simen.kjaras@gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |accepts-invalid
                 CC|                            |simen.kjaras@gmail.com
          Component|websites                    |DMD
           Platform|Other                       |All
            Version|unspecified                 |D2
           Severity|trivial                     |normal


--- Comment #1 from Simen Kjaeraas <simen.kjaras@gmail.com> 2010-12-01 05:44:53 PST ---
This is a compiler bug. Symbols used in with should shadow symbols from other with statements.

You're right however, that the spec should state this.

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bearophile_hugs@eml.cc changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |bearophile_hugs@eml.cc


--- Comment #2 from bearophile_hugs@eml.cc 2010-12-01 12:39:36 PST ---
(In reply to comment #1)
> Symbols used in with should shadow symbols from other
> with statements.

Do you mean "shouldn't"?

This shadowing is not detected, and I think the compiler has to flag this is as a compile error (just like it does with normal variables in the function stack frame):

struct X { int a; }
struct Y { int a; }
void main() {
    X x;
    Y y;
    with (x) {
        a = 2;
        with (y) {
            a = 1;
        }
    }
    assert(x.a == 2);
}

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--- Comment #3 from Simen Kjaeraas <simen.kjaras@gmail.com> 2010-12-01 14:59:32 PST ---
(In reply to comment #2)
> (In reply to comment #1)
> > Symbols used in with should shadow symbols from other
> > with statements.
> 
> Do you mean "shouldn't"?

Yes and no. It shouldn't silently do so, but it should detect that that is what is happening, and cry out loudly.

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Walter Bright <bugzilla@digitalmars.com> changed:

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


--- Comment #4 from Walter Bright <bugzilla@digitalmars.com> 2012-01-20 11:29:23 PST ---
The spec looks correct to me. The lookup order is not undefined, each successive with introduces a new scope which overrides previous scopes.

As for the shadowing, that is a bug in the compiler.

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