[Issue 10861] New: Compiler should disallow field initialization for inaccessible fields

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=10861

           Summary: Compiler should disallow field initialization for
                    inaccessible fields
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: nobody at puremagic.com
        ReportedBy: andrej.mitrovich at gmail.com


--- Comment #0 from Andrej Mitrovic <andrej.mitrovich at gmail.com> 2013-08-20 12:23:31 PDT ---
-----
module foo;

struct S
{
    int x;
    int y;

private:
    int _special;
}
-----

-----
module test;
import foo;

void main()
{
    auto s = S(1, 2, 3);
}
-----

$ dmd -c test.d
> 

The _special field was initialized, even though it's not an accessible field
from the 'test' module.

I think this is an oversight that we could fix.

The workaround is to define a custom ctor, although this might be tedious if
all that's needed is basic field initialization.

But note that there are edge cases if we try to implement this. For example:

-----
module foo;

struct S
{
    int x;
    int y;

    private int _special;

    int z;
}
-----

----
module test;

import foo;

void main()
{
    auto s = S(1, 2, 3);
}
----

If we forbid field initialization of private variables, does the above make 'z'
equal to 3 (in other words, _special is simply skipped over), or does the
compiler simply generate an error stating _special cannot be initialized from
the 'test' module?

I think the simplest and safest implementation is to always attempt field
initialization in the order of the declarations, without hiding inaccessible
fields, so the above code would produce an error.

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