http://d.puremagic.com/issues/show_bug.cgi?id=2056

           Summary: Const system does not allow certain safe
                    casts/conversions involving deep composite types
           Product: D
           Version: 2.013
          Platform: PC
        OS/Version: Windows
            Status: NEW
          Keywords: rejects-valid
          Severity: critical
          Priority: P2
         Component: DMD
        AssignedTo: bugzilla@digitalmars.com
        ReportedBy: brunodomedeiros+bugz@gmail.com


Const system does not allow certain safe casts/conversions involving deep composite types. In the following example, all casts should be allowed.
----

void testcases()
{
        int[][] intArrayArray;
        int[][][] intArrayArrayArray;


        const(int)[][] f1 = intArrayArray; // Error here
        const(int[])[] f2 = intArrayArray;

        const(int)[][][] g1 = intArrayArrayArray; // Error here
        const(int[])[][] g2 = intArrayArrayArray; // Error here
        const(int[][])[] g3 = intArrayArrayArray;

}


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------- Comment #1 from brunodomedeiros+bugz@gmail.com  2008-05-28 16:09 -------
I'm not sure if I should open a new bug or not, but since this one is still open, I'll put it here.

The array cases seem to be fixed in DMD 2.14, but the very same problem still exists with pointer types, for example:

void testcases()
{
        int** intPtrPtr;
        int*** intPtrPtrPtr;

        const(int)** h1 = intPtrPtr; // Error here
        const(int*)* h2 = intPtrPtr;

        const(int)*** i1 = intPtrPtrPtr; // Error here
        const(int*)** i2 = intPtrPtrPtr; // Error here
        const(int**)* i3 = intPtrPtrPtr;

}

Similar issues also exist for associative arrays.


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http://d.puremagic.com/issues/show_bug.cgi?id=2056


Bruno Medeiros <bdom.pub+deebugz@gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |INVALID


--- Comment #2 from Bruno Medeiros <bdom.pub+deebugz@gmail.com> 2010-11-17 12:15:17 PST ---
The latest DMD compiles both code samples now, *however*, I've come to realize that in fact this code should NOT be allowed (that is, any of the "Error here" lines in the code above should produce an error), because these casts are actually not safe.

For the reasons why, see bug #2544 , which is the inverse of this one.

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--- Comment #3 from Sobirari Muhomori <dfj1esp02@sneakemail.com> 2010-11-17 14:21:51 PST ---
So this is a regression?

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--- Comment #4 from Bruno Medeiros <bdom.pub+deebugz@gmail.com> 2010-11-18 04:06:29 PST ---
A regression? Not exactly.
When this bug was submitted, the lines marked with "// Error here" did not
compile, and that was the "bug" that was reported. At some point DMD was
changed so that the first, and later both code samples above compiled without
errors. (I don't know if it was because Walter tried to fix this "bug"
specifically, or if it was due to some other DMD changes).
So this "bug" became fixed, but as I found after seeing #2544, this "bug" is
actually invalid, and should not have been fixed in the first place.

( For curiosity, it would only be valid if immutable did not exist, or more
precisely, if T was the only subtype of const(T) )

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--- Comment #5 from Sobirari Muhomori <dfj1esp02@sneakemail.com> 2010-11-18 12:11:28 PST ---
> When this bug was submitted, the lines marked with "// Error here" did not compile

So what does the fix for bug 3621, I wonder? (It's for dmd 2.038)

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--- Comment #6 from Bruno Medeiros <bdom.pub+deebugz@gmail.com> 2010-11-19 15:20:41 PST ---
(In reply to comment #5)
> > When this bug was submitted, the lines marked with "// Error here" did not compile
> 
> So what does the fix for bug 3621, I wonder? (It's for dmd 2.038)

I don't know. The code sample in #3621 still compiles ok, so maybe it was a mistake from Walter's part, and the bug is not really fixed. Just like #2544 is not fixed.

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