Add support for Vulkan-1.3.219 validstructs attribute on <param>

We invented this attribute to denote for a param of type
`VkBaseInStructure` and `VkBaseOutStructure` what types are allowed to
be passed into it, either directly or through the `pNext` chain of
another struct (ignoring `structextends`).

vk-parse/src/parse.rs

@@ -59,7 +59,7 @@ macro_rules! unwrap_attribute (
 );
 
 macro_rules! match_attributes {
-    ($ctx:expr, $a:ident in $attributes:expr, $($p:pat => $e:expr),+) => {
+    ($ctx:expr, $a:ident in $attributes:expr, $($p:pat => $e:expr),+ $(,)?) => {
         for $a in $attributes {
             let n = $a.name.local_name.as_str();
             match n {
@@ -669,17 +669,21 @@ fn parse_command<R: Read>(ctx: &mut ParseCtx<R>, attributes: Vec<XmlAttribute>)
                 let mut optional = None;
                 let mut noautovalidity = None;
                 let mut objecttype = None;
+                let mut validstructs = None;
 
                 match_attributes!{ctx, a in attributes,
                     "len"            => len            = Some(a.value),
                     "altlen"         => altlen         = Some(a.value),
                     "externsync"     => externsync     = Some(a.value),
                     "optional"       => optional       = Some(a.value),
                     "noautovalidity" => noautovalidity = Some(a.value),
-                    "objecttype"     => objecttype     = Some(a.value)
+                    "objecttype"     => objecttype     = Some(a.value),
+                    "validstructs"   => validstructs   = Some(a.value),
                 }
 
-                if params.len() > 0 {
+                let validstructs = validstructs.unwrap_or_default().split(",").map(|s| s.to_owned()).collect();
+
+                if !params.is_empty() {
                     code.push_str(", ");
                 }
                 if let Some(definition) = parse_name_with_type(ctx, &mut code) {
@@ -691,6 +695,7 @@ fn parse_command<R: Read>(ctx: &mut ParseCtx<R>, attributes: Vec<XmlAttribute>)
                         noautovalidity,
                         objecttype,
                         definition,
+                        validstructs,
                     });
                 }
             },

vk-parse/src/types.rs

@@ -771,6 +771,16 @@ pub struct CommandParam {
         serde(default, skip_serializing_if = "is_default")
     )]
     pub definition: NameWithType,
+
+    /// only applicable for parameters which are pointers to `VkBaseInStructure` or
+    /// `VkBaseOutStructure` types, used as abstract placeholders. Specifies a list of structures
+    /// which may be passed in place of the parameter, or anywhere in the `pNext` chain of the
+    /// parameter.
+    #[cfg_attr(
+        feature = "serialize",
+        serde(default, skip_serializing_if = "is_default")
+    )]
+    pub validstructs: Vec<String>,
 }
 
 #[derive(Debug, Clone, PartialEq, Eq, Default)]