[Windows][clang] 6369267 does not compile: -Werror,-Wnull-conversion in qwen3_5.cpp (pointer passed as bool return_hidden)

[ElderOrb]

Summary

Commit 636926736c0b6053eda99d08c1f753b29938fac0 does not compile with clang on Windows
(the tree builds with -Wall -Wextra -Werror):

src/vllm/model_executor/models/qwen3_5.cpp:12483:65: error: implicit conversion of nullptr constant to 'bool' [-Werror,-Wnull-conversion]
 12480 |       lg = DenseForwardLayers(d, s.hidden->t(), s.positions, s.attn_meta,
       |            ~~~~~~~~~~~~~~~~~~
 12481 |                               s.gdn_meta, attn_kv, gdn_state, impl_->weights,
 12482 |                               impl_->config, {}, nullptr, nullptr, aux_ids_arg,
 12483 |                               aux_out_arg, dbuf ? s.dev.get() : nullptr);
       |                                                                 ^~~~~~~
       |                                                                 false
1 error generated.

Why it fires

The call passes 15 arguments; the 15th parameter of DenseForwardLayers is
bool return_hidden (signature at src/vllm/model_executor/models/qwen3_5.cpp:9822-9836),
so the pointer expression dbuf ? s.dev.get() : nullptr is converted to bool. clang
rejects the null-constant arm under -Werror,-Wnull-conversion.

Passing s.dev.get() as return_hidden also looks unintended at the call site — the 16th
parameter, StepDevInputs* persistent_sdi, is defaulted here, which suggests a reshuffled
argument list rather than an intentional value.

Environment

• Windows 11 (26200), native Windows build with clang/lld from TheRock 10.0, HIP gfx1151
• commit 6369267, -O3 -DNDEBUG -g -Xclang -gcodeview, --target server
• 9e63db5d compiles fine, so this was introduced by one of the 36 commits in between

Local workaround (to get a build)

static_cast<bool>(dbuf ? s.dev.get() : nullptr) — behaviour-preserving, but it does not
fix the likely wrong argument.

Suggested change

Pass the intended boolean (e.g. dbuf != nullptr) or the intended device argument, and make
the call site match the declared parameter list.