Auto merge of #13016 - servo:fromjsval-interface, r=jdm

Refactor some from_jsval implementations.

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components/script/dom/bindings/codegen/CodegenRust.py

@@ -3953,7 +3953,8 @@ class CGUnionConversionStruct(CGThing):
         method = CGWrapper(
             CGIndenter(CGList(conversions, "\n\n")),
             pre="unsafe fn from_jsval(cx: *mut JSContext,\n"
-                "                     value: HandleValue, _option: ())"
+                "                     value: HandleValue,\n"
+                "                     _option: ())\n"
                 "                     -> Result<ConversionResult<%s>, ()> {\n" % self.type,
             post="\n}")
         return CGWrapper(

components/script/dom/bindings/conversions.rs

@@ -104,15 +104,14 @@ impl<T: Float + FromJSValConvertible<Config=()>> FromJSValConvertible for Finite
 impl <T: Reflectable + IDLInterface> FromJSValConvertible for Root<T> {
     type Config = ();
 
-    unsafe fn from_jsval(cx: *mut JSContext,
+    unsafe fn from_jsval(_cx: *mut JSContext,
                          value: HandleValue,
                          _config: Self::Config)
                          -> Result<ConversionResult<Root<T>>, ()> {
-        let result = root_from_handlevalue(value);
+        Ok(match root_from_handlevalue(value) {
-        if let Err(()) = result {
+            Ok(result) => ConversionResult::Success(result),
-            throw_type_error(cx, "value is not an object");
+            Err(()) => ConversionResult::Failure("value is not an object".into()),
-        }
+        })
-        result.map(ConversionResult::Success)
     }
 }