Add a structural bindgen attribute

This attribute indicates that methods are to be accessed in a structural method
rather than through their class. This should allow direct access to properties
embedded on objects rather than forcing all objects to have a class/prototype.

crates/wasm-bindgen-macro/src/ast.rs

@@ -670,6 +670,16 @@ impl BindgenAttrs {
                 }
             })
     }
+
+    pub fn structural(&self) -> bool {
+        self.attrs.iter()
+            .any(|a| {
+                match *a {
+                    BindgenAttr::Structural => true,
+                    _ => false,
+                }
+            })
+    }
 }
 
 impl syn::synom::Synom for BindgenAttrs {
@@ -695,6 +705,7 @@ enum BindgenAttr {
     Module(String),
     Getter,
     Setter,
+    Structural,
 }
 
 impl syn::synom::Synom for BindgenAttr {
@@ -709,6 +720,8 @@ impl syn::synom::Synom for BindgenAttr {
         |
         call!(term, "setter") => { |_| BindgenAttr::Setter }
         |
+        call!(term, "structural") => { |_| BindgenAttr::Structural }
+        |
         do_parse!(
             call!(term, "js_namespace") >>
             punct!(=) >>

crates/wasm-bindgen-macro/src/lib.rs

@@ -349,6 +349,16 @@ impl ToTokens for ast::ImportType {
                 }
             }
 
+            impl ::wasm_bindgen::convert::FromRefWasmBoundary for #name {
+                type RefAnchor = ::std::mem::ManuallyDrop<#name>;
+                unsafe fn from_js_ref(js: Self::Js) -> Self::RefAnchor {
+                    let obj = <::wasm_bindgen::JsValue as ::wasm_bindgen::convert::WasmBoundary>
+                        ::from_js(js);
+                    ::std::mem::ManuallyDrop::new(#name { obj })
+                }
+            }
+
+
             impl From<::wasm_bindgen::JsValue> for #name {
                 fn from(obj: ::wasm_bindgen::JsValue) -> #name {
                     #name { obj }

crates/wasm-bindgen-macro/src/literal.rs

@@ -242,6 +242,7 @@ impl Literal for ast::ImportFunction {
 
         let mut getter = None;
         let mut setter = None;
+        let structural = self.function.opts.structural();
 
         if self.function.opts.getter() {
             getter = Some(self.infer_getter_property());
@@ -254,6 +255,7 @@ impl Literal for ast::ImportFunction {
             ("catch", &|a| a.bool(self.function.opts.catch())),
             ("method", &|a| a.bool(method)),
             ("js_new", &|a| a.bool(js_new)),
+            ("structural", &|a| a.bool(structural)),
             ("getter", &|a| match getter {
                 Some(ref s) => a.str(s),
                 None => a.append("null"),