[Issue 15692] Allow struct member initializer everywhere

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=15692

Alex Parrill <initrd.gz at gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |initrd.gz at gmail.com

--- Comment #1 from Alex Parrill <initrd.gz at gmail.com> ---
My use case: Vulkan uses structs to pass large amounts of parameters around. My
current code looks like this:

VkImageCreateInfo imgInfo = {
    imageType: VkImageType.VK_IMAGE_TYPE_2D,
    format: VkFormat.VK_FORMAT_R8G8B8A8_UNORM, // TODO: only allocate alpha if
needed
    extent: image.size,
    mipLevels: image.mipLevels,
    arrayLayers: image.layers,
    samples: VkSampleCountFlagBits.VK_SAMPLE_COUNT_1_BIT,
    tiling: VkImageTiling.VK_IMAGE_TILING_LINEAR, //VK_IMAGE_TILING_OPTIMAL,
    usage: VkImageUsageFlagBits.VK_IMAGE_USAGE_TRANSFER_SRC_BIT |
VkImageUsageFlagBits.VK_IMAGE_USAGE_SAMPLED_BIT,
    sharingMode: VkSharingMode.VK_SHARING_MODE_EXCLUSIVE,
    initialLayout: VkImageLayout.VK_IMAGE_LAYOUT_PREINITIALIZED,
};
enforceVK(vkCreateImage(device, &imgInfo, null, &image.img));

It'd be really nice if it were possible to specify the struct inline with the
creation call:

auto img = createImage(device, VkImageCreateInfo {
    imageType: VkImageType.VK_IMAGE_TYPE_2D,
    // ...
    initialLayout: VkImageLayout.VK_IMAGE_LAYOUT_PREINITIALIZED,
});

It'd also be very helpful for returning info structs from lamdas:

auto queueCreateInfo = priorities
    .enumerate
    .filter!(x => x[1].length > 0)
    .map!((x) {
        VkDeviceQueueCreateInfo info = {
            queueFamilyIndex: x[0],
            queueCount: cast(uint) x[1].length,
            pQueuePriorities: x[1].ptr,
        };
        return info;
    })
    .array;

You also basically have to use the the named field initialization syntax
because each Vulkan info struct begins with a `sType` field and a `pNext`
field, which at the moment should be a struct-specific constant and null that
you don't really want to specify each time you create the struct.

--