[Issue 15660] break immutable with pure function and mutable reference params

[d-bugmail--- via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=15660

github-bugzi...@puremagic.com changed:

   What|Removed |Added

 Status|NEW |RESOLVED
 Resolution|--- |FIXED

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[Issue 15660] break immutable with pure function and mutable reference params

[d-bugmail--- via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=15660

--- Comment #8 from github-bugzi...@puremagic.com ---
Commits pushed to master at https://github.com/dlang/dmd

https://github.com/dlang/dmd/commit/ab5a18635adaa3e2271e0f4b569500a89ac74235
fix Issue 15660 - break immutable with pure function and mutable reference
params

https://github.com/dlang/dmd/commit/54ab04e0ab6d27d96c78eccf10bc162fd08535cf
Merge pull request #8048 from WalterBright/fix15660

fix Issue 15660 - break immutable with pure function and mutable refe…
merged-on-behalf-of: Walter Bright <walterbri...@users.noreply.github.com>

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[Issue 15660] break immutable with pure function and mutable reference params

[d-bugmail--- via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=15660

--- Comment #7 from Walter Bright  ---
https://github.com/dlang/dmd/pull/8048

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[Issue 15660] break immutable with pure function and mutable reference params

[d-bugmail--- via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=15660

Walter Bright  changed:

   What|Removed |Added

Summary|break "immutable" with pure |break immutable with pure
   |function and mutable|function and mutable
   |reference params|reference params

--

[Issue 15660] break "immutable" with pure function and mutable reference params

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=15660

Walter Bright  changed:

   What|Removed |Added

 CC||bugzi...@digitalmars.com

--- Comment #6 from Walter Bright  ---
(In reply to Steven Schveighoffer from comment #4)
> (In reply to Iakh from comment #3)
> > (In reply to Steven Schveighoffer from comment #2)
> > Even this works:
> > import std.stdio;
> > 
> > int[] f(void[] a) @safe pure
> > {
> > return cast(int[])a;
> > }
> 
> In this case, you are using a cast. The compiler pretty much gives up trying
> to ensure anything when you cast, so I think it's OK to allow that.
> 
> Although, I thought such a cast wouldn't work in @safe code.

And indeed, it no longer is compilable:

test.d(3): Error: cast from void[] to int[] not allowed in safe code

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[Issue 15660] break "immutable" with pure function and mutable reference params

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=15660

Iakh  changed:

   What|Removed |Added

   Keywords||safe

--

[Issue 15660] break "immutable" with pure function and mutable reference params

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=15660

--- Comment #4 from Steven Schveighoffer  ---
(In reply to Iakh from comment #3)
> (In reply to Steven Schveighoffer from comment #2)
> Even this works:
> import std.stdio;
> 
> int[] f(void[] a) @safe pure
> {
> return cast(int[])a;
> }

In this case, you are using a cast. The compiler pretty much gives up trying to
ensure anything when you cast, so I think it's OK to allow that.

Although, I thought such a cast wouldn't work in @safe code.

--

[Issue 15660] break "immutable" with pure function and mutable reference params

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=15660

Steven Schveighoffer  changed:

   What|Removed |Added

Summary|breack "immutable" with |break "immutable" with pure
   |pure function and mutable   |function and mutable
   |params  |reference params

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[Issue 15660] break "immutable" with pure function and mutable reference params

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=15660

--- Comment #5 from Iakh  ---
(In reply to Steven Schveighoffer from comment #4)

> In this case, you are using a cast. The compiler pretty much gives up trying
> to ensure anything when you cast, so I think it's OK to allow that.
> 
> Although, I thought such a cast wouldn't work in @safe code.

Me too. Casting of array types does in reinterpret_cast manner. So it's a
bug in @safe definition.

--

[Issue 15660] break "immutable" with pure function and mutable reference params

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=15660

Iakh  changed:

   What|Removed |Added

URL||http://forum.dlang.org/thre
   ||ad/rdiwdveqfhevqugddwwd@for
   ||um.dlang.org

--- Comment #3 from Iakh  ---
(In reply to Steven Schveighoffer from comment #2)
Even this works:
import std.stdio;

int[] f(void[] a) @safe pure
{
return cast(int[])a;
}

void main() @safe
{
int[] a = new int[4];

immutable b = a.f();
writeln(b);
a[0] = 1;
writeln(b);
}

> One significant problem here is that the compiler may not consider the
> parameter to f in these cases to be a *return* avenue, only a parameter. The
> compiler should take into account references to ensure that they cannot
> escape the same data that is being returned.

So not only escape. Compiler just traverses params's AST and search for
exactly match with ReturnType.

> Fixing this may break a lot of code, but probably for the better. May need a
> deprecation cycle for this.

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