webidl: add support for typedefs

crates/backend/src/ast.rs

@@ -10,6 +10,7 @@ pub struct Program {
     pub imports: Vec<Import>,
     pub enums: Vec<Enum>,
     pub structs: Vec<Struct>,
+    pub type_aliases: Vec<TypeAlias>,
 }
 
 #[cfg_attr(feature = "extra-traits", derive(Debug, PartialEq, Eq))]
@@ -120,6 +121,13 @@ pub enum TypeLocation {
     ExportRet,
 }
 
+#[cfg_attr(feature = "extra-traits", derive(Debug, PartialEq, Eq))]
+pub struct TypeAlias {
+    pub vis: syn::Visibility,
+    pub dest: Ident,
+    pub src: syn::Type,
+}
+
 impl Program {
     pub fn push_item(
         &mut self,

crates/backend/src/codegen.rs

@@ -59,6 +59,9 @@ impl ToTokens for ast::Program {
         for e in self.enums.iter() {
             e.to_tokens(tokens);
         }
+        for a in self.type_aliases.iter() {
+            a.to_tokens(tokens);
+        }
 
         // Generate a static which will eventually be what lives in a custom section
         // of the wasm executable. For now it's just a plain old static, but we'll
@@ -823,3 +826,15 @@ impl ToTokens for ast::ImportStatic {
         }).to_tokens(into);
     }
 }
+
+impl ToTokens for ast::TypeAlias {
+    fn to_tokens(&self, into: &mut TokenStream) {
+        let vis = &self.vis;
+        let dest = &self.dest;
+        let src = &self.src;
+        (quote! {
+            #[allow(non_camel_case_types)]
+            #vis type #dest = #src;
+        }).to_tokens(into);
+    }
+}