Vendor dependencies

Let's see how I like this workflow.

vendor/cxx/tests/ui/deny_missing_docs.rs

@@ -0,0 +1,94 @@
+// TODO: More work is needed so that the missing_docs lints produced by rustc
+// are properly positioned inside of the bridge.
+
+//! ...
+
+#![deny(missing_docs)]
+
+/// ...
+#[cxx::bridge]
+pub mod ffi {
+    pub struct UndocumentedStruct {
+        pub undocumented_field: u8,
+    }
+
+    /// ...
+    pub struct DocumentedStruct {
+        /// ...
+        pub documented_field: u8,
+    }
+
+    pub enum UndocumentedEnum {
+        UndocumentedVariant = 0,
+    }
+
+    /// ...
+    pub enum DocumentedEnum {
+        /// ...
+        DocumentedVariant = 0,
+    }
+
+    extern "Rust" {
+        pub type UndocumentedRustType;
+
+        /// ...
+        pub type DocumentedRustType;
+
+        pub fn undocumented_rust_fn() -> u8;
+
+        /// ...
+        pub fn documented_rust_fn() -> u8;
+    }
+
+    unsafe extern "C++" {
+        pub type UndocumentedForeignType;
+
+        /// ...
+        pub type DocumentedForeignType;
+
+        pub type UndocumentedTypeAlias = crate::bindgen::UndocumentedTypeAlias;
+
+        /// ...
+        pub type DocumentedTypeAlias = crate::bindgen::DocumentedTypeAlias;
+
+        pub fn undocumented_foreign_fn() -> u8;
+
+        /// ...
+        pub fn documented_foreign_fn() -> u8;
+    }
+
+    #[allow(missing_docs)]
+    pub struct SuppressUndocumentedStruct {
+        pub undocumented_field: u8,
+    }
+}
+
+struct UndocumentedRustType;
+struct DocumentedRustType;
+
+mod bindgen {
+    use cxx::{type_id, ExternType};
+
+    pub struct UndocumentedTypeAlias;
+    pub struct DocumentedTypeAlias;
+
+    unsafe impl ExternType for UndocumentedTypeAlias {
+        type Id = type_id!("UndocumentedTypeAlias");
+        type Kind = cxx::kind::Opaque;
+    }
+
+    unsafe impl ExternType for DocumentedTypeAlias {
+        type Id = type_id!("DocumentedTypeAlias");
+        type Kind = cxx::kind::Opaque;
+    }
+}
+
+fn undocumented_rust_fn() -> u8 {
+    0
+}
+
+fn documented_rust_fn() -> u8 {
+    0
+}
+
+fn main() {}