Auto merge of #13100 - nox:better-getters, r=Ms2ger

Use Option<T> to return from getters

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30 files changed, 162 insertions, 152 deletions

diff --git a/components/script/dom/bindings/codegen/CodegenRust.py b/components/script/dom/bindings/codegen/CodegenRust.py
index 7842e08bfa7..cf918feb8e3 100644
--- a/components/script/dom/bindings/codegen/CodegenRust.py
+++ b/components/script/dom/bindings/codegen/CodegenRust.py
@@ -18,6 +18,7 @@ from WebIDL import (
     BuiltinTypes,
     IDLBuiltinType,
     IDLNullValue,
+    IDLNullableType,
     IDLType,
     IDLInterfaceMember,
     IDLUndefinedValue,
@@ -1349,7 +1350,10 @@ def getRetvalDeclarationForType(returnType, descriptorProvider):
     if returnType.isAny():
         return CGGeneric("JSVal")
     if returnType.isObject() or returnType.isSpiderMonkeyInterface():
-        return CGGeneric("*mut JSObject")
+        result = CGGeneric("NonZero<*mut JSObject>")
+        if returnType.nullable():
+            result = CGWrapper(result, pre="Option<", post=">")
+        return result
     if returnType.isSequence():
         result = getRetvalDeclarationForType(innerSequenceType(returnType), descriptorProvider)
         result = CGWrapper(result, pre="Vec<", post=">")
@@ -4552,6 +4556,8 @@ class CGProxySpecialOperation(CGPerSignatureCall):
         signature = operation.signatures()[0]
 
         (returnType, arguments) = signature
+        if operation.isGetter() and not returnType.nullable():
+            returnType = IDLNullableType(returnType.location, returnType)
 
         # We pass len(arguments) as the final argument so that the
         # CGPerSignatureCall won't do any argument conversion of its own.
@@ -4574,8 +4580,6 @@ class CGProxySpecialOperation(CGPerSignatureCall):
             self.cgRoot.prepend(instantiateJSToNativeConversionTemplate(
                 template, templateValues, declType, argument.identifier.name))
             self.cgRoot.prepend(CGGeneric("rooted!(in(cx) let value = desc.value);"))
-        elif operation.isGetter():
-            self.cgRoot.prepend(CGGeneric("let mut found = false;"))
 
     def getArguments(self):
         def process(arg):
@@ -4584,10 +4588,6 @@ class CGProxySpecialOperation(CGPerSignatureCall):
                 argVal += ".r()"
             return argVal
         args = [(a, process(a)) for a in self.arguments]
-        if self.idlNode.isGetter():
-            args.append((FakeArgument(BuiltinTypes[IDLBuiltinType.Types.boolean],
-                                      self.idlNode),
-                         "&mut found"))
         return args
 
     def wrap_return_value(self):
@@ -4595,7 +4595,7 @@ class CGProxySpecialOperation(CGPerSignatureCall):
             return ""
 
         wrap = CGGeneric(wrapForType(**self.templateValues))
-        wrap = CGIfWrapper("found", wrap)
+        wrap = CGIfWrapper("let Some(result) = result", wrap)
         return "\n" + wrap.define()
 
 
@@ -4971,7 +4971,7 @@ class CGDOMJSProxyHandler_hasOwn(CGAbstractExternMethod):
                        "    let this = UnwrapProxy(proxy);\n" +
                        "    let this = &*this;\n" +
                        CGIndenter(CGProxyIndexedGetter(self.descriptor)).define() + "\n" +
-                       "    *bp = found;\n" +
+                       "    *bp = result.is_some();\n" +
                        "    return true;\n" +
                        "}\n\n")
         else:
@@ -4987,7 +4987,7 @@ if RUST_JSID_IS_STRING(id) {
     }
     if !has_on_proto {
         %s
-        *bp = found;
+        *bp = result.is_some();
         return true;
     }
 }
@@ -5271,7 +5271,9 @@ class CGInterfaceTrait(CGThing):
 
                     infallible = 'infallible' in descriptor.getExtendedAttributes(operation)
                     if operation.isGetter():
-                        arguments = method_arguments(descriptor, rettype, arguments, trailing=("found", "&mut bool"))
+                        if not rettype.nullable():
+                            rettype = IDLNullableType(rettype.location, rettype)
+                        arguments = method_arguments(descriptor, rettype, arguments)
 
                         # If this interface 'supports named properties', then we
                         # should be able to access 'supported property names'
@@ -5323,6 +5325,7 @@ def generate_imports(config, cgthings, descriptors, callbacks=None, dictionaries
         enums = []
 
     return CGImports(cgthings, descriptors, callbacks, dictionaries, enums, [
+        'core::nonzero::NonZero',
         'js',
         'js::JSCLASS_GLOBAL_SLOT_COUNT',
         'js::JSCLASS_IS_DOMJSCLASS',
diff --git a/components/script/dom/bindings/iterable.rs b/components/script/dom/bindings/iterable.rs
index 20eb84bffde..a3092ed73b6 100644
--- a/components/script/dom/bindings/iterable.rs
+++ b/components/script/dom/bindings/iterable.rs
@@ -6,6 +6,7 @@
 
 //! Implementation of `iterable<...>` and `iterable<..., ...>` WebIDL declarations.
 
+use core::nonzero::NonZero;
 use dom::bindings::codegen::Bindings::IterableIteratorBinding::IterableKeyAndValueResult;
 use dom::bindings::codegen::Bindings::IterableIteratorBinding::IterableKeyOrValueResult;
 use dom::bindings::error::Fallible;
@@ -95,38 +96,41 @@ impl<T: Reflectable + JSTraceable + Iterable> IterableIterator<T> {
 
     /// Return the next value from the iterable object.
     #[allow(non_snake_case)]
-    pub fn Next(&self, cx: *mut JSContext) -> Fallible<*mut JSObject> {
+    pub fn Next(&self, cx: *mut JSContext) -> Fallible<NonZero<*mut JSObject>> {
         let index = self.index.get();
         rooted!(in(cx) let mut value = UndefinedValue());
         rooted!(in(cx) let mut rval = ptr::null_mut());
-        if index >= self.iterable.get_iterable_length() {
-            return dict_return(cx, rval.handle_mut(), true, value.handle())
-                .map(|_| rval.handle().get());
-        }
-        let result = match self.type_ {
-            IteratorType::Keys => {
-                unsafe {
-                    self.iterable.get_key_at_index(index).to_jsval(cx, value.handle_mut());
+        let result = if index >= self.iterable.get_iterable_length() {
+            dict_return(cx, rval.handle_mut(), true, value.handle())
+        } else {
+            match self.type_ {
+                IteratorType::Keys => {
+                    unsafe {
+                        self.iterable.get_key_at_index(index).to_jsval(cx, value.handle_mut());
+                    }
+                    dict_return(cx, rval.handle_mut(), false, value.handle())
                 }
-                dict_return(cx, rval.handle_mut(), false, value.handle())
-            }
-            IteratorType::Values => {
-                unsafe {
-                    self.iterable.get_value_at_index(index).to_jsval(cx, value.handle_mut());
+                IteratorType::Values => {
+                    unsafe {
+                        self.iterable.get_value_at_index(index).to_jsval(cx, value.handle_mut());
+                    }
+                    dict_return(cx, rval.handle_mut(), false, value.handle())
                 }
-                dict_return(cx, rval.handle_mut(), false, value.handle())
-            }
-            IteratorType::Entries => {
-                rooted!(in(cx) let mut key = UndefinedValue());
-                unsafe {
-                    self.iterable.get_key_at_index(index).to_jsval(cx, key.handle_mut());
-                    self.iterable.get_value_at_index(index).to_jsval(cx, value.handle_mut());
+                IteratorType::Entries => {
+                    rooted!(in(cx) let mut key = UndefinedValue());
+                    unsafe {
+                        self.iterable.get_key_at_index(index).to_jsval(cx, key.handle_mut());
+                        self.iterable.get_value_at_index(index).to_jsval(cx, value.handle_mut());
+                    }
+                    key_and_value_return(cx, rval.handle_mut(), key.handle(), value.handle())
                 }
-                key_and_value_return(cx, rval.handle_mut(), key.handle(), value.handle())
             }
         };
         self.index.set(index + 1);
-        result.map(|_| rval.handle().get())
+        result.map(|_| {
+            assert!(!rval.is_null());
+            unsafe { NonZero::new(rval.get()) }
+        })
     }
 }
 
diff --git a/components/script/dom/canvasrenderingcontext2d.rs b/components/script/dom/canvasrenderingcontext2d.rs
index f3c74b59250..61cc2520165 100644
--- a/components/script/dom/canvasrenderingcontext2d.rs
+++ b/components/script/dom/canvasrenderingcontext2d.rs
@@ -1100,7 +1100,7 @@ impl CanvasRenderingContext2DMethods for CanvasRenderingContext2D {
                      dirtyY: Finite<f64>,
                      dirtyWidth: Finite<f64>,
                      dirtyHeight: Finite<f64>) {
-        let data = imagedata.get_data_array(&self.global().r());
+        let data = imagedata.get_data_array();
         let offset = Point2D::new(*dx, *dy);
         let image_data_size = Size2D::new(imagedata.Width() as f64, imagedata.Height() as f64);
 
diff --git a/components/script/dom/crypto.rs b/components/script/dom/crypto.rs
index 6e0351d37ee..165a3834227 100644
--- a/components/script/dom/crypto.rs
+++ b/components/script/dom/crypto.rs
@@ -2,6 +2,7 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
+use core::nonzero::NonZero;
 use dom::bindings::cell::DOMRefCell;
 use dom::bindings::codegen::Bindings::CryptoBinding;
 use dom::bindings::codegen::Bindings::CryptoBinding::CryptoMethods;
@@ -43,7 +44,8 @@ impl CryptoMethods for Crypto {
     fn GetRandomValues(&self,
                        _cx: *mut JSContext,
                        input: *mut JSObject)
-                       -> Fallible<*mut JSObject> {
+                       -> Fallible<NonZero<*mut JSObject>> {
+        assert!(!input.is_null());
         let mut data = match unsafe { array_buffer_view_data::<u8>(input) } {
             Some(data) => data,
             None => {
@@ -62,7 +64,7 @@ impl CryptoMethods for Crypto {
 
         self.rng.borrow_mut().fill_bytes(&mut data);
 
-        Ok(input)
+        Ok(unsafe { NonZero::new(input) })
     }
 }
 
diff --git a/components/script/dom/cssstyledeclaration.rs b/components/script/dom/cssstyledeclaration.rs
index 076a2283b67..0335a7498c0 100644
--- a/components/script/dom/cssstyledeclaration.rs
+++ b/components/script/dom/cssstyledeclaration.rs
@@ -100,18 +100,7 @@ impl CSSStyleDeclarationMethods for CSSStyleDeclaration {
 
     // https://dev.w3.org/csswg/cssom/#dom-cssstyledeclaration-item
     fn Item(&self, index: u32) -> DOMString {
-        let index = index as usize;
-        let elem = self.owner.upcast::<Element>();
-        let style_attribute = elem.style_attribute().borrow();
-        style_attribute.as_ref().and_then(|declarations| {
-            declarations.declarations.get(index)
-        }).map(|&(ref declaration, importance)| {
-            let mut css = declaration.to_css_string();
-            if importance.important() {
-                css += " !important";
-            }
-            DOMString::from(css)
-        }).unwrap_or_else(DOMString::new)
+        self.IndexedGetter(index).unwrap_or_default()
     }
 
     // https://dev.w3.org/csswg/cssom/#dom-cssstyledeclaration-getpropertyvalue
@@ -333,10 +322,19 @@ impl CSSStyleDeclarationMethods for CSSStyleDeclaration {
     }
 
     // https://dev.w3.org/csswg/cssom/#the-cssstyledeclaration-interface
-    fn IndexedGetter(&self, index: u32, found: &mut bool) -> DOMString {
-        let rval = self.Item(index);
-        *found = index < self.Length();
-        rval
+    fn IndexedGetter(&self, index: u32) -> Option<DOMString> {
+        let index = index as usize;
+        let elem = self.owner.upcast::<Element>();
+        let style_attribute = elem.style_attribute().borrow();
+        style_attribute.as_ref().and_then(|declarations| {
+            declarations.declarations.get(index)
+        }).map(|&(ref declaration, importance)| {
+            let mut css = declaration.to_css_string();
+            if importance.important() {
+                css += " !important";
+            }
+            DOMString::from(css)
+        })
     }
 
     // https://drafts.csswg.org/cssom/#dom-cssstyledeclaration-csstext
diff --git a/components/script/dom/document.rs b/components/script/dom/document.rs
index 58995645c27..f6f06e7d851 100644
--- a/components/script/dom/document.rs
+++ b/components/script/dom/document.rs
@@ -2,6 +2,7 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
+use core::nonzero::NonZero;
 use document_loader::{DocumentLoader, LoadType};
 use dom::activation::{ActivationSource, synthetic_click_activation};
 use dom::attr::Attr;
@@ -116,7 +117,6 @@ use std::collections::hash_map::Entry::{Occupied, Vacant};
 use std::default::Default;
 use std::iter::once;
 use std::mem;
-use std::ptr;
 use std::rc::Rc;
 use std::sync::Arc;
 use string_cache::{Atom, QualName};
@@ -2710,8 +2710,9 @@ impl DocumentMethods for Document {
         self.set_body_attribute(&atom!("text"), value)
     }
 
+    #[allow(unsafe_code)]
     // https://html.spec.whatwg.org/multipage/#dom-tree-accessors:dom-document-nameditem-filter
-    fn NamedGetter(&self, _cx: *mut JSContext, name: DOMString, found: &mut bool) -> *mut JSObject {
+    fn NamedGetter(&self, _cx: *mut JSContext, name: DOMString) -> Option<NonZero<*mut JSObject>> {
         #[derive(JSTraceable, HeapSizeOf)]
         struct NamedElementFilter {
             name: Atom,
@@ -2777,23 +2778,24 @@ impl DocumentMethods for Document {
                                    .peekable();
             if let Some(first) = elements.next() {
                 if elements.peek().is_none() {
-                    *found = true;
                     // TODO: Step 2.
                     // Step 3.
-                    return first.reflector().get_jsobject().get();
+                    return unsafe {
+                        Some(NonZero::new(first.reflector().get_jsobject().get()))
+                    };
                 }
             } else {
-                *found = false;
-                return ptr::null_mut();
+                return None;
             }
         }
         // Step 4.
-        *found = true;
         let filter = NamedElementFilter {
             name: name,
         };
         let collection = HTMLCollection::create(self.window(), root, box filter);
-        collection.reflector().get_jsobject().get()
+        unsafe {
+            Some(NonZero::new(collection.reflector().get_jsobject().get()))
+        }
     }
 
     // https://html.spec.whatwg.org/multipage/#dom-tree-accessors:supported-property-names
diff --git a/components/script/dom/domrectlist.rs b/components/script/dom/domrectlist.rs
index adb246158f4..86774a49ff3 100644
--- a/components/script/dom/domrectlist.rs
+++ b/components/script/dom/domrectlist.rs
@@ -52,8 +52,7 @@ impl DOMRectListMethods for DOMRectList {
     }
 
     // check-tidy: no specs after this line
-    fn IndexedGetter(&self, index: u32, found: &mut bool) -> Option<Root<DOMRect>> {
-        *found = index < self.rects.len() as u32;
+    fn IndexedGetter(&self, index: u32) -> Option<Root<DOMRect>> {
         self.Item(index)
     }
 }
diff --git a/components/script/dom/domstringmap.rs b/components/script/dom/domstringmap.rs
index c5e534d242e..11479d6b5df 100644
--- a/components/script/dom/domstringmap.rs
+++ b/components/script/dom/domstringmap.rs
@@ -47,10 +47,8 @@ impl DOMStringMapMethods for DOMStringMap {
     }
 
     // https://html.spec.whatwg.org/multipage/#dom-domstringmap-nameditem
-    fn NamedGetter(&self, name: DOMString, found: &mut bool) -> DOMString {
-        let attr = self.element.get_custom_attr(name);
-        *found = attr.is_some();
-        attr.unwrap_or_default()
+    fn NamedGetter(&self, name: DOMString) -> Option<DOMString> {
+        self.element.get_custom_attr(name)
     }
 
     // https://html.spec.whatwg.org/multipage/#the-domstringmap-interface:supported-property-names
diff --git a/components/script/dom/domtokenlist.rs b/components/script/dom/domtokenlist.rs
index 364b6366282..c1c09de94c2 100644
--- a/components/script/dom/domtokenlist.rs
+++ b/components/script/dom/domtokenlist.rs
@@ -171,9 +171,7 @@ impl DOMTokenListMethods for DOMTokenList {
     }
 
     // check-tidy: no specs after this line
-    fn IndexedGetter(&self, index: u32, found: &mut bool) -> Option<DOMString> {
-        let item = self.Item(index);
-        *found = item.is_some();
-        item
+    fn IndexedGetter(&self, index: u32) -> Option<DOMString> {
+        self.Item(index)
     }
 }
diff --git a/components/script/dom/filelist.rs b/components/script/dom/filelist.rs
index 4f8e976f5f7..8adbe1ed467 100644
--- a/components/script/dom/filelist.rs
+++ b/components/script/dom/filelist.rs
@@ -55,9 +55,7 @@ impl FileListMethods for FileList {
     }
 
     // check-tidy: no specs after this line
-    fn IndexedGetter(&self, index: u32, found: &mut bool) -> Option<Root<File>> {
-        let item = self.Item(index);
-        *found = item.is_some();
-        item
+    fn IndexedGetter(&self, index: u32) -> Option<Root<File>> {
+        self.Item(index)
     }
 }
diff --git a/components/script/dom/htmlcanvaselement.rs b/components/script/dom/htmlcanvaselement.rs
index 45c1916f928..73b51962fe4 100644
--- a/components/script/dom/htmlcanvaselement.rs
+++ b/components/script/dom/htmlcanvaselement.rs
@@ -273,11 +273,10 @@ impl HTMLCanvasElementMethods for HTMLCanvasElement {
         // Step 3.
         let raw_data = match *self.context.borrow() {
             Some(CanvasContext::Context2d(ref context)) => {
-                let window = window_from_node(self);
                 let image_data = try!(context.GetImageData(Finite::wrap(0f64), Finite::wrap(0f64),
                                                            Finite::wrap(self.Width() as f64),
                                                            Finite::wrap(self.Height() as f64)));
-                image_data.get_data_array(&GlobalRef::Window(window.r()))
+                image_data.get_data_array()
             }
             None => {
                 // Each pixel is fully-transparent black.
diff --git a/components/script/dom/htmlcollection.rs b/components/script/dom/htmlcollection.rs
index 95134556bc0..2f226590719 100644
--- a/components/script/dom/htmlcollection.rs
+++ b/components/script/dom/htmlcollection.rs
@@ -317,17 +317,13 @@ impl HTMLCollectionMethods for HTMLCollection {
     }
 
     // https://dom.spec.whatwg.org/#dom-htmlcollection-item
-    fn IndexedGetter(&self, index: u32, found: &mut bool) -> Option<Root<Element>> {
-        let maybe_elem = self.Item(index);
-        *found = maybe_elem.is_some();
-        maybe_elem
+    fn IndexedGetter(&self, index: u32) -> Option<Root<Element>> {
+        self.Item(index)
     }
 
     // check-tidy: no specs after this line
-    fn NamedGetter(&self, name: DOMString, found: &mut bool) -> Option<Root<Element>> {
-        let maybe_elem = self.NamedItem(name);
-        *found = maybe_elem.is_some();
-        maybe_elem
+    fn NamedGetter(&self, name: DOMString) -> Option<Root<Element>> {
+        self.NamedItem(name)
     }
 
     // https://dom.spec.whatwg.org/#interface-htmlcollection
diff --git a/components/script/dom/htmlformcontrolscollection.rs b/components/script/dom/htmlformcontrolscollection.rs
index 9229b854b26..e52a541225f 100644
--- a/components/script/dom/htmlformcontrolscollection.rs
+++ b/components/script/dom/htmlformcontrolscollection.rs
@@ -77,10 +77,8 @@ impl HTMLFormControlsCollectionMethods for HTMLFormControlsCollection {
     }
 
     // https://html.spec.whatwg.org/multipage/#dom-htmlformcontrolscollection-nameditem
-    fn NamedGetter(&self, name: DOMString, found: &mut bool) -> Option<RadioNodeListOrElement> {
-        let maybe_elem = self.NamedItem(name);
-        *found = maybe_elem.is_some();
-        maybe_elem
+    fn NamedGetter(&self, name: DOMString) -> Option<RadioNodeListOrElement> {
+        self.NamedItem(name)
     }
 
     // https://html.spec.whatwg.org/multipage/#the-htmlformcontrolscollection-interface:supported-property-names
@@ -93,7 +91,7 @@ impl HTMLFormControlsCollectionMethods for HTMLFormControlsCollection {
     // https://github.com/servo/servo/issues/5875
     //
     // https://dom.spec.whatwg.org/#dom-htmlcollection-item
-    fn IndexedGetter(&self, index: u32, found: &mut bool) -> Option<Root<Element>> {
-        self.collection.IndexedGetter(index, found)
+    fn IndexedGetter(&self, index: u32) -> Option<Root<Element>> {
+        self.collection.IndexedGetter(index)
     }
 }
diff --git a/components/script/dom/htmlformelement.rs b/components/script/dom/htmlformelement.rs
index db9e3cb8d41..fa16618b564 100644
--- a/components/script/dom/htmlformelement.rs
+++ b/components/script/dom/htmlformelement.rs
@@ -230,9 +230,9 @@ impl HTMLFormElementMethods for HTMLFormElement {
     }
 
     // https://html.spec.whatwg.org/multipage/#dom-form-item
-    fn IndexedGetter(&self, index: u32, found: &mut bool) -> Option<Root<Element>> {
+    fn IndexedGetter(&self, index: u32) -> Option<Root<Element>> {
         let elements = self.Elements();
-        elements.IndexedGetter(index, found)
+        elements.IndexedGetter(index)
     }
 }
 
diff --git a/components/script/dom/imagedata.rs b/components/script/dom/imagedata.rs
index abcb9b5640b..0959a52eb32 100644
--- a/components/script/dom/imagedata.rs
+++ b/components/script/dom/imagedata.rs
@@ -2,6 +2,7 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
+use core::nonzero::NonZero;
 use dom::bindings::codegen::Bindings::ImageDataBinding;
 use dom::bindings::codegen::Bindings::ImageDataBinding::ImageDataMethods;
 use dom::bindings::global::GlobalRef;
@@ -37,6 +38,7 @@ impl ImageData {
         unsafe {
             let cx = global.get_cx();
             let js_object: *mut JSObject = JS_NewUint8ClampedArray(cx, width * height * 4);
+            assert!(!js_object.is_null());
 
             if let Some(vec) = data {
                 let mut is_shared = false;
@@ -52,12 +54,13 @@ impl ImageData {
     }
 
     #[allow(unsafe_code)]
-    pub fn get_data_array(&self, global: &GlobalRef) -> Vec<u8> {
+    pub fn get_data_array(&self) -> Vec<u8> {
         unsafe {
-            let cx = global.get_cx();
             let mut is_shared = false;
+            assert!(!self.data.get().is_null());
             let data: *const uint8_t =
-                JS_GetUint8ClampedArrayData(self.Data(cx), &mut is_shared, ptr::null()) as *const uint8_t;
+                JS_GetUint8ClampedArrayData(self.data.get(), &mut is_shared, ptr::null()) as *const uint8_t;
+            assert!(!data.is_null());
             assert!(!is_shared);
             let len = self.Width() * self.Height() * 4;
             slice::from_raw_parts(data, len as usize).to_vec()
@@ -80,8 +83,10 @@ impl ImageDataMethods for ImageData {
         self.height
     }
 
+    #[allow(unsafe_code)]
     // https://html.spec.whatwg.org/multipage/#dom-imagedata-data
-    fn Data(&self, _: *mut JSContext) -> *mut JSObject {
-        self.data.get()
+    fn Data(&self, _: *mut JSContext) -> NonZero<*mut JSObject> {
+        assert!(!self.data.get().is_null());
+        unsafe { NonZero::new(self.data.get()) }
     }
 }
diff --git a/components/script/dom/mimetypearray.rs b/components/script/dom/mimetypearray.rs
index 96fc48c86d0..de820f6d06a 100644
--- a/components/script/dom/mimetypearray.rs
+++ b/components/script/dom/mimetypearray.rs
@@ -46,12 +46,12 @@ impl MimeTypeArrayMethods for MimeTypeArray {
     }
 
     // https://html.spec.whatwg.org/multipage/#dom-mimetypearray-item
-    fn IndexedGetter(&self, _index: u32, _found: &mut bool) -> Option<Root<MimeType>> {
+    fn IndexedGetter(&self, _index: u32) -> Option<Root<MimeType>> {
         None
     }
 
     // check-tidy: no specs after this line
-    fn NamedGetter(&self, _name: DOMString, _found: &mut bool) -> Option<Root<MimeType>> {
+    fn NamedGetter(&self, _name: DOMString) -> Option<Root<MimeType>> {
         None
     }
 
diff --git a/components/script/dom/namednodemap.rs b/components/script/dom/namednodemap.rs
index 10b6b8982ae..9edc1b1e93b 100644
--- a/components/script/dom/namednodemap.rs
+++ b/components/script/dom/namednodemap.rs
@@ -85,17 +85,13 @@ impl NamedNodeMapMethods for NamedNodeMap {
     }
 
     // https://dom.spec.whatwg.org/#dom-namednodemap-item
-    fn IndexedGetter(&self, index: u32, found: &mut bool) -> Option<Root<Attr>> {
-        let item = self.Item(index);
-        *found = item.is_some();
-        item
+    fn IndexedGetter(&self, index: u32) -> Option<Root<Attr>> {
+        self.Item(index)
     }
 
     // check-tidy: no specs after this line
-    fn NamedGetter(&self, name: DOMString, found: &mut bool) -> Option<Root<Attr>> {
-        let item = self.GetNamedItem(name);
-        *found = item.is_some();
-        item
+    fn NamedGetter(&self, name: DOMString) -> Option<Root<Attr>> {
+        self.GetNamedItem(name)
     }
 
     // https://heycam.github.io/webidl/#dfn-supported-property-names
diff --git a/components/script/dom/nodelist.rs b/components/script/dom/nodelist.rs
index 2503378187e..8f8a5515592 100644
--- a/components/script/dom/nodelist.rs
+++ b/components/script/dom/nodelist.rs
@@ -75,10 +75,8 @@ impl NodeListMethods for NodeList {
     }
 
     // https://dom.spec.whatwg.org/#dom-nodelist-item
-    fn IndexedGetter(&self, index: u32, found: &mut bool) -> Option<Root<Node>> {
-        let item = self.Item(index);
-        *found = item.is_some();
-        item
+    fn IndexedGetter(&self, index: u32) -> Option<Root<Node>> {
+        self.Item(index)
     }
 }
 
diff --git a/components/script/dom/plugin.rs b/components/script/dom/plugin.rs
index dc4ca4fe42d..222e9a2840a 100644
--- a/components/script/dom/plugin.rs
+++ b/components/script/dom/plugin.rs
@@ -45,12 +45,12 @@ impl PluginMethods for Plugin {
     }
 
     // https://html.spec.whatwg.org/multipage/#dom-plugin-item
-    fn IndexedGetter(&self, _index: u32, _found: &mut bool) -> Option<Root<MimeType>> {
+    fn IndexedGetter(&self, _index: u32) -> Option<Root<MimeType>> {
         unreachable!()
     }
 
     // check-tidy: no specs after this line
-    fn NamedGetter(&self, _name: DOMString, _found: &mut bool) -> Option<Root<MimeType>> {
+    fn NamedGetter(&self, _name: DOMString) -> Option<Root<MimeType>> {
         unreachable!()
     }
 
diff --git a/components/script/dom/pluginarray.rs b/components/script/dom/pluginarray.rs
index aabba4928a4..aa6b779280d 100644
--- a/components/script/dom/pluginarray.rs
+++ b/components/script/dom/pluginarray.rs
@@ -50,12 +50,12 @@ impl PluginArrayMethods for PluginArray {
     }
 
     // https://html.spec.whatwg.org/multipage/#dom-pluginarray-item
-    fn IndexedGetter(&self, _index: u32, _found: &mut bool) -> Option<Root<Plugin>> {
+    fn IndexedGetter(&self, _index: u32) -> Option<Root<Plugin>> {
         None
     }
 
     // check-tidy: no specs after this line
-    fn NamedGetter(&self, _name: DOMString, _found: &mut bool) -> Option<Root<Plugin>> {
+    fn NamedGetter(&self, _name: DOMString) -> Option<Root<Plugin>> {
         None
     }
 
diff --git a/components/script/dom/radionodelist.rs b/components/script/dom/radionodelist.rs
index d88fc69eacd..9bbdae00c85 100644
--- a/components/script/dom/radionodelist.rs
+++ b/components/script/dom/radionodelist.rs
@@ -105,7 +105,7 @@ impl RadioNodeListMethods for RadioNodeList {
     // https://github.com/servo/servo/issues/5875
     //
     // https://dom.spec.whatwg.org/#dom-nodelist-item
-    fn IndexedGetter(&self, index: u32, found: &mut bool) -> Option<Root<Node>> {
-        self.node_list.IndexedGetter(index, found)
+    fn IndexedGetter(&self, index: u32) -> Option<Root<Node>> {
+        self.node_list.IndexedGetter(index)
     }
 }
diff --git a/components/script/dom/storage.rs b/components/script/dom/storage.rs
index d6d1e1968f8..7827cdb6b15 100644
--- a/components/script/dom/storage.rs
+++ b/components/script/dom/storage.rs
@@ -136,10 +136,8 @@ impl StorageMethods for Storage {
     }
 
     // check-tidy: no specs after this line
-    fn NamedGetter(&self, name: DOMString, found: &mut bool) -> Option<DOMString> {
-        let item = self.GetItem(name);
-        *found = item.is_some();
-        item
+    fn NamedGetter(&self, name: DOMString) -> Option<DOMString> {
+        self.GetItem(name)
     }
 
     fn NamedSetter(&self, name: DOMString, value: DOMString) -> ErrorResult {
diff --git a/components/script/dom/stylesheetlist.rs b/components/script/dom/stylesheetlist.rs
index 1b7eb643e50..721ac06525c 100644
--- a/components/script/dom/stylesheetlist.rs
+++ b/components/script/dom/stylesheetlist.rs
@@ -46,9 +46,7 @@ impl StyleSheetListMethods for StyleSheetList {
     }
 
     // check-tidy: no specs after this line
-    fn IndexedGetter(&self, index: u32, found: &mut bool) -> Option<Root<StyleSheet>>{
-        let item = self.Item(index);
-        *found = item.is_some();
-        item
+    fn IndexedGetter(&self, index: u32) -> Option<Root<StyleSheet>> {
+        self.Item(index)
     }
 }
diff --git a/components/script/dom/testbinding.rs b/components/script/dom/testbinding.rs
index 9143c8b0188..21439c0b19a 100644
--- a/components/script/dom/testbinding.rs
+++ b/components/script/dom/testbinding.rs
@@ -4,6 +4,7 @@
 
 // check-tidy: no specs after this line
 
+use core::nonzero::NonZero;
 use dom::bindings::codegen::Bindings::EventListenerBinding::EventListener;
 use dom::bindings::codegen::Bindings::FunctionBinding::Function;
 use dom::bindings::codegen::Bindings::TestBindingBinding;
@@ -26,6 +27,7 @@ use dom::bindings::weakref::MutableWeakRef;
 use dom::blob::{Blob, BlobImpl};
 use dom::url::URL;
 use js::jsapi::{HandleObject, HandleValue, JSContext, JSObject};
+use js::jsapi::{JS_NewPlainObject, JS_NewUint8ClampedArray};
 use js::jsval::{JSVal, NullValue};
 use std::borrow::ToOwned;
 use std::ptr;
@@ -137,10 +139,24 @@ impl TestBindingMethods for TestBinding {
         ByteStringOrLong::ByteString(ByteString::new(vec!()))
     }
     fn SetUnion9Attribute(&self, _: ByteStringOrLong) {}
-    fn ArrayAttribute(&self, _: *mut JSContext) -> *mut JSObject { NullValue().to_object_or_null() }
+    #[allow(unsafe_code)]
+    fn ArrayAttribute(&self, cx: *mut JSContext) -> NonZero<*mut JSObject> {
+        unsafe {
+            rooted!(in(cx) let array = JS_NewUint8ClampedArray(cx, 16));
+            assert!(!array.is_null());
+            NonZero::new(array.get())
+        }
+    }
     fn AnyAttribute(&self, _: *mut JSContext) -> JSVal { NullValue() }
     fn SetAnyAttribute(&self, _: *mut JSContext, _: HandleValue) {}
-    fn ObjectAttribute(&self, _: *mut JSContext) -> *mut JSObject { panic!() }
+    #[allow(unsafe_code)]
+    fn ObjectAttribute(&self, cx: *mut JSContext) -> NonZero<*mut JSObject> {
+        unsafe {
+            rooted!(in(cx) let obj = JS_NewPlainObject(cx));
+            assert!(!obj.is_null());
+            NonZero::new(obj.get())
+        }
+    }
     fn SetObjectAttribute(&self, _: *mut JSContext, _: *mut JSObject) {}
 
     fn GetBooleanAttributeNullable(&self) -> Option<bool> { Some(false) }
@@ -193,7 +209,7 @@ impl TestBindingMethods for TestBinding {
     fn SetInterfaceAttributeWeak(&self, url: Option<&URL>) {
         self.url.set(url);
     }
-    fn GetObjectAttributeNullable(&self, _: *mut JSContext) -> *mut JSObject { ptr::null_mut() }
+    fn GetObjectAttributeNullable(&self, _: *mut JSContext) -> Option<NonZero<*mut JSObject>> { None }
     fn SetObjectAttributeNullable(&self, _: *mut JSContext, _: *mut JSObject) {}
     fn GetUnionAttributeNullable(&self) -> Option<HTMLElementOrLong> {
         Some(HTMLElementOrLong::Long(0))
@@ -242,7 +258,9 @@ impl TestBindingMethods for TestBinding {
         Blob::new(self.global().r(), BlobImpl::new_from_bytes(vec![]), "".to_owned())
     }
     fn ReceiveAny(&self, _: *mut JSContext) -> JSVal { NullValue() }
-    fn ReceiveObject(&self, _: *mut JSContext) -> *mut JSObject { panic!() }
+    fn ReceiveObject(&self, cx: *mut JSContext) -> NonZero<*mut JSObject> {
+        self.ObjectAttribute(cx)
+    }
     fn ReceiveUnion(&self) -> HTMLElementOrLong { HTMLElementOrLong::Long(0) }
     fn ReceiveUnion2(&self) -> EventOrString { EventOrString::String(DOMString::new()) }
     fn ReceiveUnion3(&self) -> StringOrLongSequence { StringOrLongSequence::LongSequence(vec![]) }
@@ -283,7 +301,9 @@ impl TestBindingMethods for TestBinding {
     fn ReceiveNullableInterface(&self) -> Option<Root<Blob>> {
         Some(Blob::new(self.global().r(), BlobImpl::new_from_bytes(vec![]), "".to_owned()))
     }
-    fn ReceiveNullableObject(&self, _: *mut JSContext) -> *mut JSObject { ptr::null_mut() }
+    fn ReceiveNullableObject(&self, cx: *mut JSContext) -> Option<NonZero<*mut JSObject>> {
+        self.GetObjectAttributeNullable(cx)
+    }
     fn ReceiveNullableUnion(&self) -> Option<HTMLElementOrLong> {
         Some(HTMLElementOrLong::Long(0))
     }
diff --git a/components/script/dom/testbindingiterable.rs b/components/script/dom/testbindingiterable.rs
index 1e462a98531..2ad0df6dbb6 100644
--- a/components/script/dom/testbindingiterable.rs
+++ b/components/script/dom/testbindingiterable.rs
@@ -34,10 +34,8 @@ impl TestBindingIterable {
 impl TestBindingIterableMethods for TestBindingIterable {
     fn Add(&self, v: DOMString) { self.vals.borrow_mut().push(v); }
     fn Length(&self) -> u32 { self.vals.borrow().len() as u32 }
-    fn GetItem(&self, n: u32) -> DOMString { self.vals.borrow().get(n as usize).unwrap().clone() }
-    fn IndexedGetter(&self, n: u32, found: &mut bool) -> DOMString {
-        let s = self.GetItem(n);
-        *found = true;
-        s
+    fn GetItem(&self, n: u32) -> DOMString { self.IndexedGetter(n).unwrap_or_default() }
+    fn IndexedGetter(&self, n: u32) -> Option<DOMString> {
+        self.vals.borrow().get(n as usize).cloned()
     }
 }
diff --git a/components/script/dom/testbindingproxy.rs b/components/script/dom/testbindingproxy.rs
index 3308639305c..45e66bc5919 100644
--- a/components/script/dom/testbindingproxy.rs
+++ b/components/script/dom/testbindingproxy.rs
@@ -23,10 +23,10 @@ impl TestBindingProxyMethods for TestBindingProxy {
     fn SetItem(&self, _: u32, _: DOMString) -> () {}
     fn RemoveItem(&self, _: DOMString) -> () {}
     fn Stringifier(&self) -> DOMString { DOMString::new() }
-    fn IndexedGetter(&self, _: u32, _: &mut bool) -> DOMString { DOMString::new() }
+    fn IndexedGetter(&self, _: u32) -> Option<DOMString> { None }
     fn NamedDeleter(&self, _: DOMString) -> () {}
     fn IndexedSetter(&self, _: u32, _: DOMString) -> () {}
     fn NamedSetter(&self, _: DOMString, _: DOMString) -> () {}
-    fn NamedGetter(&self, _: DOMString, _: &mut bool) -> DOMString { DOMString::new() }
+    fn NamedGetter(&self, _: DOMString) -> Option<DOMString> { None }
 
 }
diff --git a/components/script/dom/textencoder.rs b/components/script/dom/textencoder.rs
index 84100e723ba..674243dded8 100644
--- a/components/script/dom/textencoder.rs
+++ b/components/script/dom/textencoder.rs
@@ -2,6 +2,7 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
+use core::nonzero::NonZero;
 use dom::bindings::codegen::Bindings::TextEncoderBinding;
 use dom::bindings::codegen::Bindings::TextEncoderBinding::TextEncoderMethods;
 use dom::bindings::error::{Error, Fallible};
@@ -70,16 +71,17 @@ impl TextEncoderMethods for TextEncoder {
 
     #[allow(unsafe_code)]
     // https://encoding.spec.whatwg.org/#dom-textencoder-encode
-    fn Encode(&self, cx: *mut JSContext, input: USVString) -> *mut JSObject {
+    fn Encode(&self, cx: *mut JSContext, input: USVString) -> NonZero<*mut JSObject> {
         unsafe {
             let encoded = self.encoder.encode(&input.0, EncoderTrap::Strict).unwrap();
             let length = encoded.len() as u32;
-            let js_object: *mut JSObject = JS_NewUint8Array(cx, length);
+            rooted!(in(cx) let js_object = JS_NewUint8Array(cx, length));
+            assert!(!js_object.is_null());
             let mut is_shared = false;
-            let js_object_data: *mut uint8_t = JS_GetUint8ArrayData(js_object, &mut is_shared, ptr::null());
+            let js_object_data: *mut uint8_t = JS_GetUint8ArrayData(js_object.get(), &mut is_shared, ptr::null());
             assert!(!is_shared);
             ptr::copy_nonoverlapping(encoded.as_ptr(), js_object_data, length as usize);
-            js_object
+            NonZero::new(js_object.get())
         }
     }
 }
diff --git a/components/script/dom/touchlist.rs b/components/script/dom/touchlist.rs
index ae5313e855e..14bb8a68766 100644
--- a/components/script/dom/touchlist.rs
+++ b/components/script/dom/touchlist.rs
@@ -42,9 +42,7 @@ impl TouchListMethods for TouchList {
     }
 
     /// https://w3c.github.io/touch-events/#widl-TouchList-item-getter-Touch-unsigned-long-index
-    fn IndexedGetter(&self, index: u32, found: &mut bool) -> Option<Root<Touch>> {
-        let item = self.Item(index);
-        *found = item.is_some();
-        item
+    fn IndexedGetter(&self, index: u32) -> Option<Root<Touch>> {
+        self.Item(index)
     }
 }
diff --git a/components/script/dom/webglrenderingcontext.rs b/components/script/dom/webglrenderingcontext.rs
index 5ff793527ec..aadf03d4211 100644
--- a/components/script/dom/webglrenderingcontext.rs
+++ b/components/script/dom/webglrenderingcontext.rs
@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use canvas_traits::{CanvasCommonMsg, CanvasMsg, byte_swap};
+use core::nonzero::NonZero;
 use dom::bindings::codegen::Bindings::WebGLRenderingContextBinding::WebGLRenderingContextConstants as constants;
 use dom::bindings::codegen::Bindings::WebGLRenderingContextBinding::WebGLRenderingContextMethods;
 use dom::bindings::codegen::Bindings::WebGLRenderingContextBinding::{self, WebGLContextAttributes};
@@ -305,8 +306,7 @@ impl WebGLRenderingContext {
         // complexity is worth it.
         let (pixels, size) = match source {
             ImageDataOrHTMLImageElementOrHTMLCanvasElementOrHTMLVideoElement::ImageData(image_data) => {
-                let global = self.global();
-                (image_data.get_data_array(&global.r()), image_data.get_size())
+                (image_data.get_data_array(), image_data.get_size())
             },
             ImageDataOrHTMLImageElementOrHTMLCanvasElementOrHTMLVideoElement::HTMLImageElement(image) => {
                 let img_url = match image.get_url() {
@@ -632,8 +632,9 @@ impl WebGLRenderingContextMethods for WebGLRenderingContext {
     }
 
     // https://www.khronos.org/registry/webgl/specs/latest/1.0/#5.14.14
-    fn GetExtension(&self, _cx: *mut JSContext, _name: DOMString) -> *mut JSObject {
-        0 as *mut JSObject
+    fn GetExtension(&self, _cx: *mut JSContext, _name: DOMString)
+                    -> Option<NonZero<*mut JSObject>> {
+        None
     }
 
     // https://www.khronos.org/registry/webgl/specs/latest/1.0/#5.14.3
diff --git a/components/script/dom/xmldocument.rs b/components/script/dom/xmldocument.rs
index 5f6b6e1919c..1a00f67b80c 100644
--- a/components/script/dom/xmldocument.rs
+++ b/components/script/dom/xmldocument.rs
@@ -2,6 +2,7 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
+use core::nonzero::NonZero;
 use document_loader::DocumentLoader;
 use dom::bindings::codegen::Bindings::DocumentBinding::DocumentMethods;
 use dom::bindings::codegen::Bindings::XMLDocumentBinding::{self, XMLDocumentMethods};
@@ -87,7 +88,7 @@ impl XMLDocumentMethods for XMLDocument {
     }
 
     // https://html.spec.whatwg.org/multipage/#dom-tree-accessors:dom-document-nameditem-filter
-    fn NamedGetter(&self, _cx: *mut JSContext, name: DOMString, found: &mut bool) -> *mut JSObject {
-        self.upcast::<Document>().NamedGetter(_cx, name, found)
+    fn NamedGetter(&self, _cx: *mut JSContext, name: DOMString) -> Option<NonZero<*mut JSObject>> {
+        self.upcast::<Document>().NamedGetter(_cx, name)
     }
 }