[PATCH v3 2/6] rust: doctest: add LocalModule fallback for #[vtable] ThisModule

[Alvin Sun <alvin.sun@linux.dev>]

Add a `LocalModule` struct with a null-pointer `ModuleMetadata` impl
in the doctest harness, so that `crate::LocalModule` (auto-inserted
by `#[vtable]`) resolves correctly when there is no `module!` macro.

Reviewed-by: Andreas Hindborg <a.hindborg@kernel.org>
Signed-off-by: Alvin Sun <alvin.sun@linux.dev>
---
 scripts/rustdoc_test_gen.rs | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/scripts/rustdoc_test_gen.rs b/scripts/rustdoc_test_gen.rs
index ee76e96b41eea..198af4e446c8c 100644
--- a/scripts/rustdoc_test_gen.rs
+++ b/scripts/rustdoc_test_gen.rs
@@ -239,6 +239,22 @@ macro_rules! assert_eq {{
 
 const __LOG_PREFIX: &[u8] = b"rust_doctests_kernel\0";
 
+/// Dummy module type for doctest context.
+struct LocalModule;
+
+use kernel::{{
+    str::CStr,
+    ModuleMetadata,
+    ThisModule, //
+}};
+use core::ptr::null_mut;
+
+impl ModuleMetadata for LocalModule {{
+    const NAME: &'static CStr = c"rust_doctests_kernel";
+    // SAFETY: `try_module_get`/`module_put` handle null module pointers gracefully.
+    const THIS_MODULE: ThisModule = unsafe {{ ThisModule::from_ptr(null_mut()) }};
+}}
+
 {rust_tests}
 "#
     )

-- 
2.43.0