ci: Test docs in addition to cargo t --all-targets (#392)

* ci: Test docs in addition to `cargo t --all-targets`

Unfortunately docs are not explicitly (build-)tested as part of
`--all-targets` allowing broken code to slip in as shown by #390.

Also remove the `rust` listing type which is the default, leaving only
`no_run` (until the CI has a loadable Vulkan library).

* ash: Fix errors and warnings in (now tested) documentation comments

.github/workflows/ci.yml

@@ -53,10 +53,16 @@ jobs:
           profile: minimal
           toolchain: stable
           override: true
-      - uses: actions-rs/cargo@v1
+      - name: Test all targets
+        uses: actions-rs/cargo@v1
         with:
           command: test
           args: --workspace --all-targets
+      - name: Test docs
+        uses: actions-rs/cargo@v1
+        with:
+          command: test
+          args: --workspace --doc
 
   fmt:
     name: Rustfmt

ash/src/entry.rs

@@ -191,10 +191,10 @@ impl<L> EntryCustom<L> {
     }
 
     #[doc = "<https://www.khronos.org/registry/vulkan/specs/1.2-extensions/man/html/vkEnumerateInstanceVersion.html>"]
-    /// ```rust,no_run
+    /// ```no_run
     /// # use ash::{Entry, vk};
-    /// # fn main() -> Result<(), Box<std::error::Error>> {
+    /// # fn main() -> Result<(), Box<dyn std::error::Error>> {
-    /// let entry = Entry::new()?;
+    /// let entry = unsafe { Entry::new() }?;
     /// match entry.try_enumerate_instance_version()? {
     ///     // Vulkan 1.1+
     ///     Some(version) => {

ash/src/entry_libloading.rs

@@ -46,10 +46,10 @@ impl EntryCustom<Arc<Library>> {
     /// `dlopen`ing native libraries is inherently unsafe. The safety guidelines
     /// for [`Library::new`] and [`Library::get`] apply here.
     ///
-    /// ```rust,no_run
+    /// ```no_run
     /// use ash::{vk, Entry, version::EntryV1_0};
-    /// # fn main() -> Result<(), Box<std::error::Error>> {
+    /// # fn main() -> Result<(), Box<dyn std::error::Error>> {
-    /// let entry = Entry::new()?;
+    /// let entry = unsafe { Entry::new() }?;
     /// let app_info = vk::ApplicationInfo {
     ///     api_version: vk::make_version(1, 0, 0),
     ///     ..Default::default()

ash/src/lib.rs

@@ -5,10 +5,10 @@
 //!
 //! ## Examples
 //!
-//! ```rust,no_run
+//! ```no_run
 //! use ash::{vk, Entry, version::EntryV1_0};
 //! # fn main() -> Result<(), Box<dyn std::error::Error>> {
-//! let entry = Entry::new()?;
+//! let entry = unsafe { Entry::new() }?;
 //! let app_info = vk::ApplicationInfo {
 //!     api_version: vk::make_version(1, 0, 0),
 //!     ..Default::default()