`@cImport` "union depends on itself" regression

[ypsvlq]

Zig Version

0.12.0-dev.601+f4c884617

Steps to Reproduce and Observed Behavior

// zig build-exe -target x86_64-windows -lc

const c = @cImport(@cInclude("audioclient.h"));

pub fn main() !void {
 var x: c.TYPEDESC = undefined;
 _ = x;
}

cimport.zig:43579:34: error: union '...cimport.union_unnamed_290' depends on itself
const union_unnamed_290 = extern union {
 ~~~~~~~^~~~~
cimport.zig:43585:5: note: while checking this field
 unnamed_0: union_unnamed_290 = @import("std").mem.zeroes(union_unnamed_290),
 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~```

mingw header:

typedef struct tagTYPEDESC {
 __C89_NAMELESS union {
 struct tagTYPEDESC *lptdesc;
 struct tagARRAYDESC *lpadesc;
 HREFTYPE hreftype;
 } __C89_NAMELESSUNIONNAME;
 VARTYPE vt;
} TYPEDESC;

cimport.zig:

const union_unnamed_290 = extern union {
 lptdesc: [*c]struct_tagTYPEDESC,
 lpadesc: [*c]struct_tagARRAYDESC,
 hreftype: HREFTYPE,
};
pub const struct_tagTYPEDESC = extern struct {
 unnamed_0: union_unnamed_290 = @import("std").mem.zeroes(union_unnamed_290),
 vt: VARTYPE = @import("std").mem.zeroes(VARTYPE),
};
pub const TYPEDESC = struct_tagTYPEDESC;

Expected Behavior

Compiles successfully in 0.11.0

[Vexu]

I cannot reproduce this with 0.12.0-dev.601+f4c884617.

[ypsvlq]

It still occurs for me using that version. Reverting #17196 restores the old behaviour.

[jayschwa]

I can reproduce with 0.12.0-dev.596+2adb932ad.

[Vexu]

Can you make a reduction?

[jayschwa]

The example in the original post did it for me, but I'll try to do one that isn't dependent on Windows target. It looks like the gist is a union type that contains a struct type which contains a pointer to the union type.

[mlugg]

I suspect resolving this would require separating alignment resolution for unions in the same way we've done for structs.

[ypsvlq]

After looking into it more, the actual problem is the second member of the union:

pub const ARRAYDESC = struct {
 tdescElem: TYPEDESC = @import("std").mem.zeroes(TYPEDESC),
};

const union_unnamed_279 = union {
 lptdesc: ?*TYPEDESC,
 lpadesc: ?*ARRAYDESC,
};

pub const TYPEDESC = struct {
 unnamed_0: union_unnamed_279 = @import("std").mem.zeroes(union_unnamed_279),
};

pub fn main() !void {
 var x: TYPEDESC = undefined;
 _ = x;
}

[kcbanner]

I'm going to start working on a fix for this