[Issue 11858] Comparison of unconnected classes using `is` must be disallowed

[d-bugmail]

https://d.puremagic.com/issues/show_bug.cgi?id=11858


Denis Shelomovskij verylonglogin@gmail.com changed:

   What|Removed |Added

   Severity|enhancement |major


--- Comment #3 from Denis Shelomovskij verylonglogin@gmail.com 2014-01-05 
19:20:19 MSK ---
(In reply to comment #2)
 This isn't accepts-invalid, because there's no rule against it.  It's an
 enhancement request.

It's still a bug as current dmd behaviour is inconsistent as if both types are
qualified the compiler rejects such comparison.

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[Issue 11858] Comparison of unconnected classes using `is` must be disallowed

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https://d.puremagic.com/issues/show_bug.cgi?id=11858


Stewart Gordon s...@iname.com changed:

   What|Removed |Added

   Keywords||spec


--- Comment #4 from Stewart Gordon s...@iname.com 2014-01-05 15:22:40 PST ---
Hmm.  There's a concept of a reinterpret cast with pointers, so an int* and a
float* can feasibly be pointing to the same memory address.  Since it's far
less likely that this will be done with object references, I see now that it
would need to be at least as strict to make sense.

Looking at

http://dlang.org/expression.html#IdentityExpression

there isn't a clear statement of what combinations of types are allowed.  There
should be.  As such, this is a spec issue as much as a compiler issue.

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[Issue 11858] Comparison of unconnected classes using `is` must be disallowed

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https://d.puremagic.com/issues/show_bug.cgi?id=11858


Stewart Gordon s...@iname.com changed:

   What|Removed |Added

   Keywords|accepts-invalid |
 CC||s...@iname.com
   Severity|major   |enhancement


--- Comment #2 from Stewart Gordon s...@iname.com 2014-01-03 05:53:13 PST ---
This isn't accepts-invalid, because there's no rule against it.  It's an
enhancement request.

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[Issue 11858] Comparison of unconnected classes using `is` must be disallowed

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https://d.puremagic.com/issues/show_bug.cgi?id=11858


Andrej Mitrovic andrej.mitrov...@gmail.com changed:

   What|Removed |Added

 CC||andrej.mitrov...@gmail.com


--- Comment #1 from Andrej Mitrovic andrej.mitrov...@gmail.com 2014-01-02 
13:10:49 PST ---
I think this would definitely catch some bugs. I wonder what kind of impact it
would have on code breakage though (perhaps we would go through a warning phase
first). 

There is definitely a precedent:

-
void main()
{
int* a;
float* b;
static assert(!__traits(compiles, a is b)); // ok, not allowed
}
-

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