[Issue 16357] cast(T[])[x] casts x to T instead of [x] to T[]

Feb 17, 2019

Vladimir Panteleev

Jun 21, 2021

ag0aep6g

Oct 04, 2023

Oct 06, 2023

Oct 06, 2023

Nov 08, 2023

Nov 08, 2023

https://issues.dlang.org/show_bug.cgi?id=16357 Vladimir Panteleev <dlang-bugzilla@thecybershadow.net> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |dkorpel@live.nl --- Comment #1 from Vladimir Panteleev <dlang-bugzilla@thecybershadow.net> --- *** Issue 19683 has been marked as a duplicate of this issue. *** --

https://issues.dlang.org/show_bug.cgi?id=16357 ag0aep6g <ag0aep6g@gmail.com> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |eyal@weka.io --- Comment #2 from ag0aep6g <ag0aep6g@gmail.com> --- *** Issue 22055 has been marked as a duplicate of this issue. *** --

October 04, 2023

[Issue 16357] cast(T[])[x] casts x to T instead of [x] to T[]

Posted by Steven Schveighoffer

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Steven Schveighoffer

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https://issues.dlang.org/show_bug.cgi?id=16357

Steven Schveighoffer <schveiguy@gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |spec
                 CC|                            |schveiguy@gmail.com

--- Comment #3 from Steven Schveighoffer <schveiguy@gmail.com> ---
This is technically in the spec: https://dlang.org/spec/expression.html#cast_array_literal

Quoting:
```
When array literals are cast to another array type, each element of the array
is cast to the new element type.
```

But I don't know if the spec (which only shows casting arrays with elements of
value 1) or this issue (which has elements of value 0) explores the destructive
nature of the current implementation:

```d
void main()
{
    uint x = 0x12345;
    ubyte[] data = cast(ubyte[])[x];
    assert(data == [0x45]); // we lost the extra bytes!
}
```

My thought is that this should either be an error, or a warning in the spec is warranted.

--

https://issues.dlang.org/show_bug.cgi?id=16357 Dlang Bot <dlang-bot@dlang.rocks> changed: What |Removed |Added ---------------------------------------------------------------------------- Keywords| |pull --- Comment #4 from Dlang Bot <dlang-bot@dlang.rocks> --- @ntrel updated dlang/dlang.org pull request #3701 "[spec] Array literal can implicitly convert to an expected type" fixing this issue: - Show overflow in example Fix Issue 16357 - cast(T[])[x] casts x to T instead of [x] to T[]. https://github.com/dlang/dlang.org/pull/3701 --

https://issues.dlang.org/show_bug.cgi?id=16357 Nick Treleaven <nick@geany.org> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |nick@geany.org --- Comment #5 from Nick Treleaven <nick@geany.org> --- I've made a PR to update the spec. I don't think we can make that an error without risking existing code breakage. --

https://issues.dlang.org/show_bug.cgi?id=16357 Dlang Bot <dlang-bot@dlang.rocks> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|NEW |RESOLVED Resolution|--- |FIXED --- Comment #6 from Dlang Bot <dlang-bot@dlang.rocks> --- dlang/dlang.org pull request #3701 "[spec] Array literal can implicitly convert to an expected type" was merged into master: - 4e8db30f0bf3c330c3431e83fe8a75f843b40857 by Nick Treleaven: Show overflow in example Fix Issue 16357 - cast(T[])[x] casts x to T instead of [x] to T[]. https://github.com/dlang/dlang.org/pull/3701 --

https://issues.dlang.org/show_bug.cgi?id=16357 Steven Schveighoffer <schveiguy@gmail.com> changed: What |Removed |Added ---------------------------------------------------------------------------- Resolution|FIXED |WONTFIX --- Comment #7 from Steven Schveighoffer <schveiguy@gmail.com> --- I'm changing this to WONTFIX because the original bug report is against the behavior, not that it wasn't explained properly. --

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