[Issue 10980] static initialization of immutable structs with disabled postblit fails

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=10980


Kenji Hara <k.hara.pg at gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |pull, rejects-valid
            Summary|[reg] static initialization |static initialization of
                   |of immutable structs with   |immutable structs with
                   |disabled postblit fails     |disabled postblit fails
           Severity|regression                  |blocker


--- Comment #1 from Kenji Hara <k.hara.pg at gmail.com> 2013-09-08 23:34:36 PDT ---
(In reply to comment #0)
> Let S be a struct a disabled potsblit, and we want to create a static instance
> of an immutable S:
> 
> //----
> alias immutable(S) IS;
> static IS i = IS.init;
> //----
> 
> 2.060: OK!
> 2.061: Error: variablei of type struct immutable(S) uses this(this), which is
> not allowed in static initialization
> 2.062: Error: variable hello.i of type struct immutable(S) uses this(this),
> which is not allowed in static initialization
> 2.063: OK!
> 2.063.2: OK!
> 
> So... it broke and it was fixed (apparently).

The issue had not been fixed, instead it just be hidden by the regression bug
10998, from 2.063.

> BUT!
> Let's try that in a template now:
> 
> //----
> template foo(T)
> {
>     static T i = T.init;
>     alias i foo;
> }
> 
> struct S
> {
>     @disable this(this);
> }
> alias immutable(S) IS;
> 
> //IS i = IS.init; //Uncoment me
> 
> void main()
> {
>     auto p = &foo!IS;
> }
> //----
> 2.060: OK!
> 2.061: Error: variable main.i of type struct immutable(S) uses this(this),
> which is not allowed in static initialization
> 2.062: Error: variable main.i of type struct immutable(S) uses this(this),
> which is not allowed in static initialization
> 2.063: Error: template instance main.foo!(immutable(S)) error instantiating
> 2.063.2: Error: template instance main.foo!(immutable(S)) error instantiating
> 
> Now, we simply have an "unclear" error that the template failed, but with no
> diagnostics (at least, I am unable to provide any).
> 
> Funny story: if we uncomment the global static, it works again. Another
> workaround is to declare the static inside a function, and have the function
> return the static by reference.
> 
> This issue is also "semi-blocker" in emplace, which needs to create a static
> instance of T, no matter T's type.

Because the current compile-time postblit call check is not enough strict. I
opened a compiler fix to improve check mechanism.

https://github.com/D-Programming-Language/dmd/pull/2541

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