[spec/struct] Add 'Union Literals' & 'Anonymous Structs & Unions'

[ntrel]

The docs for a struct literal with a union field apply for non-anonymous unions too.
Fix: Non-overlapping union field data is not default initialized, it is
zeroed.
Fixes Issues 21188, 18855.

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Bugzilla references

Auto-close	Bugzilla	Severity	Description
✓	18855	minor	Behavior of Anonymous Union is Undocumented
✓	21188	normal	Anonymous structs - not described

[dkorpel]

I think the text could be more precise in what an anonymous struct/union does instead of what it's used for. It doesn't cover arbitrarily complex / redundant usages: struct S { struct { struct { union { struct { int x; }}}}} Still, it's a good start.

[PetarKirov]

@ntrel please update the commit message, so that all of the issues will be automatically closed by @dlang-bot. See: https://github.com/dlang/dlang-bot#referencing-multiple-issues

[RazvanN7]

Hmm, the commit message does contain both issues, I wonder why the bot doesn't catch that. @ntrel the quick fix would be to just break your commit into 2, each fixing one of the issues.

[PetarKirov]

I think the commit message should start with the issues that are fixed. Try this:

Fix issues 18855 and 21188 - [spec/struct] Add 'Union Literals' & 'Anonymous Structs & Unions' 

Fix Issue 21188 - Anonymous structs - not described.
Fix Issue 18855 - Behavior of Anonymous Union is Undocumented.

Fix: Non-overlapping union field data is not default initialized, it is
zeroed.

See: https://regex101.com/r/C7q7eT/1

[ntrel]

@PetarKirov @RazvanN7 Updated commit message as suggested. No changes to diff.

[ntrel]

@PetarKirov Do you know which file in dlang-bot has the regex to detect fixed issues? I'd like to have a look.

[PetarKirov]

Do you know which file in dlang-bot has the regex to detect fixed issues? I'd like to have a look.

I think this is what you're looking for: https://github.com/dlang/dlang-bot/blob/750bb49423033c0bc52d2515fde2b29238668265/source/dlangbot/bugzilla.d#L21