vulkan : fix unclosed brace in turbo type guard (backend never compiled)

[skulze]

Problem

The Vulkan backend on feature/turboquant-kv-cache does not compile. The turbo-type guard added to ggml_backend_vk_device_supports_op (around line 17603 of ggml-vulkan.cpp) opens a block that is never closed:

if (op->type == GGML_TYPE_TURBO2_0 || ... TURBO4_0) {
    if (op->src[0]->ne[0] % 128 != 0 || op->src[0]->type != GGML_TYPE_F32) {
    return false;
}                     // closes the inner if only
switch (op->type) {   // now nested inside the never-closed turbo guard

Every subsequent function definition in the file is parsed as nested, so a -DGGML_VULKAN=ON build fails with a wall of:

error: a function-definition is not allowed here before '{' token

Fix

Close the guard so it validates the turbo constraint (head_dim divisible by 128, f32 source) and falls through to the existing type switch — which already handles GGML_TYPE_TURBO{2,3,4}_0 — as clearly intended.

Verified

Built with -DGGML_VULKAN=ON -DGGML_NATIVE=ON -DCMAKE_BUILD_TYPE=Release (0 errors) and served Qwen3.6-35B-A3B-UD-Q4_K_XL-MTP on an AMD Radeon AI PRO R9700 (RDNA4/gfx1201, RADV, Mesa 25.2.8) with -ctk turbo3 -ctv turbo3 --spec-type draft-mtp -c 262144. Turbo KV, MTP speculation and 256K context all work; measured 139 t/s decode with -ub 2048.

🤖 Generated with Claude Code

[worthant]

feature/turboquant-kv-cache is a legacy branch

latest is master and dev

please check if this issue persist there. I suppose not, because i checked that Vulkan should work there