Auto merge of #15927 - lucantrop:master, r=Ms2ger

added tidiness check for "-> ()"

<!-- Please describe your changes on the following line: -->
I added the check, modified the tests and removed all instances of "-> ()" that were already there.

---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data: -->
- [ ] `./mach build -d` does not report any errors
- [ ] `./mach test-tidy` does not report any errors
- [ ] These changes fix #15925 (github issue number if applicable).

<!-- Either: -->
- [X] There are tests for these changes

<!-- Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process. -->

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---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/15927)
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components/devtools/actors/timeline.rs

@@ -288,7 +288,7 @@ impl Emitter {
         }
     }
 
-    fn send(&mut self, markers: Vec<TimelineMarkerReply>) -> () {
+    fn send(&mut self, markers: Vec<TimelineMarkerReply>) {
         let end_time = PreciseTime::now();
         let reply = MarkersEmitterReply {
             type_: "markers".to_owned(),

components/script/dom/bluetoothdevice.rs

@@ -251,7 +251,7 @@ impl BluetoothDeviceMethods for BluetoothDevice {
     }
 
     // https://webbluetoothcg.github.io/web-bluetooth/#dom-bluetoothdevice-unwatchadvertisements
-    fn UnwatchAdvertisements(&self) -> () {
+    fn UnwatchAdvertisements(&self) {
         // Step 1.
         self.watching_advertisements.set(false)
         // TODO: Step 2.

components/script/dom/canvasrenderingcontext2d.rs

@@ -888,7 +888,7 @@ impl CanvasRenderingContext2DMethods for CanvasRenderingContext2D {
     }
 
     // https://html.spec.whatwg.org/multipage/#dom-context-2d-imagesmoothingenabled
-    fn SetImageSmoothingEnabled(&self, value: bool) -> () {
+    fn SetImageSmoothingEnabled(&self, value: bool) {
         self.state.borrow_mut().image_smoothing_enabled = value;
     }
 

components/script/dom/testbinding.rs

@@ -247,8 +247,8 @@ impl TestBindingMethods for TestBinding {
         Some(ByteStringOrLong::ByteString(ByteString::new(vec!())))
     }
     fn SetUnion6AttributeNullable(&self, _: Option<ByteStringOrLong>) {}
-    fn BinaryRenamedMethod(&self) -> () {}
+    fn BinaryRenamedMethod(&self) {}
-    fn ReceiveVoid(&self) -> () {}
+    fn ReceiveVoid(&self) {}
     fn ReceiveBoolean(&self) -> bool { false }
     fn ReceiveByte(&self) -> i8 { 0 }
     fn ReceiveOctet(&self) -> u8 { 0 }

components/script/dom/testbindingproxy.rs

@@ -18,15 +18,15 @@ impl TestBindingProxyMethods for TestBindingProxy {
     fn Length(&self) -> u32 { 0 }
     fn SupportedPropertyNames(&self) -> Vec<DOMString> { vec![] }
     fn GetNamedItem(&self, _: DOMString) -> DOMString { DOMString::new() }
-    fn SetNamedItem(&self, _: DOMString, _: DOMString) -> () {}
+    fn SetNamedItem(&self, _: DOMString, _: DOMString) {}
     fn GetItem(&self, _: u32) -> DOMString { DOMString::new() }
-    fn SetItem(&self, _: u32, _: DOMString) -> () {}
+    fn SetItem(&self, _: u32, _: DOMString) {}
-    fn RemoveItem(&self, _: DOMString) -> () {}
+    fn RemoveItem(&self, _: DOMString) {}
     fn Stringifier(&self) -> DOMString { DOMString::new() }
     fn IndexedGetter(&self, _: u32) -> Option<DOMString> { None }
-    fn NamedDeleter(&self, _: DOMString) -> () {}
+    fn NamedDeleter(&self, _: DOMString) {}
-    fn IndexedSetter(&self, _: u32, _: DOMString) -> () {}
+    fn IndexedSetter(&self, _: u32, _: DOMString) {}
-    fn NamedSetter(&self, _: DOMString, _: DOMString) -> () {}
+    fn NamedSetter(&self, _: DOMString, _: DOMString) {}
     fn NamedGetter(&self, _: DOMString) -> Option<DOMString> { None }
 
 }

components/script/dom/vrdisplay.rs

@@ -203,7 +203,7 @@ impl VRDisplayMethods for VRDisplay {
     }
 
     // https://w3c.github.io/webvr/#dom-vrdisplay-resetpose
-    fn ResetPose(&self) -> () {
+    fn ResetPose(&self) {
         let (sender, receiver) = ipc::channel().unwrap();
         self.webvr_thread().send(WebVRMsg::ResetPose(self.global().pipeline_id(),
                                                      self.get_display_id(),
@@ -220,7 +220,7 @@ impl VRDisplayMethods for VRDisplay {
     }
 
     // https://w3c.github.io/webvr/#dom-vrdisplay-depthnear
-    fn SetDepthNear(&self, value: Finite<f64>) -> () {
+    fn SetDepthNear(&self, value: Finite<f64>) {
         self.depth_near.set(*value.deref());
     }
 
@@ -230,7 +230,7 @@ impl VRDisplayMethods for VRDisplay {
     }
 
     // https://w3c.github.io/webvr/#dom-vrdisplay-depthfar
-    fn SetDepthFar(&self, value: Finite<f64>) -> () {
+    fn SetDepthFar(&self, value: Finite<f64>) {
         self.depth_far.set(*value.deref());
     }
 
@@ -249,7 +249,7 @@ impl VRDisplayMethods for VRDisplay {
     }
 
     // https://w3c.github.io/webvr/#dom-vrdisplay-cancelanimationframe
-    fn CancelAnimationFrame(&self, handle: u32) -> () {
+    fn CancelAnimationFrame(&self, handle: u32) {
         if self.presenting.get() {
             let mut list = self.raf_callback_list.borrow_mut();
             if let Some(mut pair) = list.iter_mut().find(|pair| pair.0 == handle) {
@@ -364,7 +364,7 @@ impl VRDisplayMethods for VRDisplay {
     }
 
     // https://w3c.github.io/webvr/#dom-vrdisplay-submitframe
-    fn SubmitFrame(&self) -> () {
+    fn SubmitFrame(&self) {
         if !self.presenting.get() {
             warn!("VRDisplay not presenting");
             return;

components/style/gecko/arc_types.rs

@@ -27,12 +27,12 @@ macro_rules! impl_arc_ffi {
         unsafe impl HasArcFFI for $servo_type {}
 
         #[no_mangle]
-        pub unsafe extern "C" fn $addref(obj: &$gecko_type) -> () {
+        pub unsafe extern "C" fn $addref(obj: &$gecko_type) {
             <$servo_type>::addref(obj);
         }
 
         #[no_mangle]
-        pub unsafe extern "C" fn $release(obj: &$gecko_type) -> () {
+        pub unsafe extern "C" fn $release(obj: &$gecko_type) {
             <$servo_type>::release(obj);
         }
     }

ports/geckolib/glue.rs

@@ -132,7 +132,7 @@ lazy_static! {
 }
 
 #[no_mangle]
-pub extern "C" fn Servo_Initialize() -> () {
+pub extern "C" fn Servo_Initialize() {
     // Initialize logging.
     let mut builder = LogBuilder::new();
     let default_level = if cfg!(debug_assertions) { "warn" } else { "error" };
@@ -152,7 +152,7 @@ pub extern "C" fn Servo_Initialize() -> () {
 }
 
 #[no_mangle]
-pub extern "C" fn Servo_Shutdown() -> () {
+pub extern "C" fn Servo_Shutdown() {
     // Clear some static data to avoid shutdown leaks.
     gecko_properties::shutdown();
 }
@@ -321,7 +321,7 @@ pub extern "C" fn Servo_StyleWorkerThreadCount() -> u32 {
 }
 
 #[no_mangle]
-pub extern "C" fn Servo_Element_ClearData(element: RawGeckoElementBorrowed) -> () {
+pub extern "C" fn Servo_Element_ClearData(element: RawGeckoElementBorrowed) {
     GeckoElement(element).clear_data();
 }
 
@@ -500,7 +500,7 @@ pub extern "C" fn Servo_StyleSheet_GetRules(sheet: RawServoStyleSheetBorrowed) -
 
 #[no_mangle]
 pub extern "C" fn Servo_CssRules_ListTypes(rules: ServoCssRulesBorrowed,
-                                           result: nsTArrayBorrowed_uintptr_t) -> () {
+                                           result: nsTArrayBorrowed_uintptr_t) {
     let rules = RwLock::<CssRules>::as_arc(&rules).read();
     let iter = rules.0.iter().map(|rule| rule.rule_type() as usize);
     let (size, upper) = iter.size_hint();
@@ -559,7 +559,7 @@ pub extern "C" fn Servo_CssRules_DeleteRule(rules: ServoCssRulesBorrowed, index:
 }
 
 #[no_mangle]
-pub extern "C" fn Servo_StyleRule_Debug(rule: RawServoStyleRuleBorrowed, result: *mut nsACString) -> () {
+pub extern "C" fn Servo_StyleRule_Debug(rule: RawServoStyleRuleBorrowed, result: *mut nsACString) {
     let rule = RwLock::<StyleRule>::as_arc(&rule);
     let result = unsafe { result.as_mut().unwrap() };
     write!(result, "{:?}", *rule.read()).unwrap();
@@ -573,26 +573,26 @@ pub extern "C" fn Servo_StyleRule_GetStyle(rule: RawServoStyleRuleBorrowed) -> R
 
 #[no_mangle]
 pub extern "C" fn Servo_StyleRule_SetStyle(rule: RawServoStyleRuleBorrowed,
-                                           declarations: RawServoDeclarationBlockBorrowed) -> () {
+                                           declarations: RawServoDeclarationBlockBorrowed) {
     let rule = RwLock::<StyleRule>::as_arc(&rule);
     let declarations = RwLock::<PropertyDeclarationBlock>::as_arc(&declarations);
     rule.write().block = declarations.clone();
 }
 
 #[no_mangle]
-pub extern "C" fn Servo_StyleRule_GetCssText(rule: RawServoStyleRuleBorrowed, result: *mut nsAString) -> () {
+pub extern "C" fn Servo_StyleRule_GetCssText(rule: RawServoStyleRuleBorrowed, result: *mut nsAString) {
     let rule = RwLock::<StyleRule>::as_arc(&rule);
     rule.read().to_css(unsafe { result.as_mut().unwrap() }).unwrap();
 }
 
 #[no_mangle]
-pub extern "C" fn Servo_StyleRule_GetSelectorText(rule: RawServoStyleRuleBorrowed, result: *mut nsAString) -> () {
+pub extern "C" fn Servo_StyleRule_GetSelectorText(rule: RawServoStyleRuleBorrowed, result: *mut nsAString) {
     let rule = RwLock::<StyleRule>::as_arc(&rule);
     rule.read().selectors.to_css(unsafe { result.as_mut().unwrap() }).unwrap();
 }
 
 #[no_mangle]
-pub extern "C" fn Servo_MediaRule_Debug(rule: RawServoMediaRuleBorrowed, result: *mut nsACString) -> () {
+pub extern "C" fn Servo_MediaRule_Debug(rule: RawServoMediaRuleBorrowed, result: *mut nsACString) {
     let rule = RwLock::<MediaRule>::as_arc(&rule);
     let result = unsafe { result.as_mut().unwrap() };
     write!(result, "{:?}", *rule.read()).unwrap();
@@ -611,7 +611,7 @@ pub extern "C" fn Servo_MediaRule_GetRules(rule: RawServoMediaRuleBorrowed) -> S
 }
 
 #[no_mangle]
-pub extern "C" fn Servo_MediaRule_GetCssText(rule: RawServoMediaRuleBorrowed, result: *mut nsAString) -> () {
+pub extern "C" fn Servo_MediaRule_GetCssText(rule: RawServoMediaRuleBorrowed, result: *mut nsAString) {
     let rule = RwLock::<MediaRule>::as_arc(&rule);
     rule.read().to_css(unsafe { result.as_mut().unwrap() }).unwrap();
 }
@@ -712,7 +712,7 @@ pub extern "C" fn Servo_StyleSet_RebuildData(raw_data: RawServoStyleSetBorrowed)
 }
 
 #[no_mangle]
-pub extern "C" fn Servo_StyleSet_Drop(data: RawServoStyleSetOwned) -> () {
+pub extern "C" fn Servo_StyleSet_Drop(data: RawServoStyleSetOwned) {
     let _ = data.into_box::<PerDocumentStyleData>();
 }
 

python/tidy/servo_tidy/tidy.py

@@ -565,6 +565,8 @@ def check_rust(file_name, lines):
             # This particular pattern is not reentrant-safe in script_thread.rs
             (r"match self.documents.borrow", "use a separate variable for the match expression",
              lambda match, line: file_name.endswith('script_thread.rs')),
+            # -> () is unnecessary
+            (r"-> \(\)", "encountered function signature with -> ()", no_filter),
         ]
 
         for pattern, message, filter_func in regex_rules:

python/tidy/servo_tidy_tests/rust_tidy.rs

@@ -38,7 +38,7 @@ impl test {
         }
     }
 
-    fn test_fun2(y : &String, z : &Vec<f32>, r: &Root<isize>) -> f32 {
+    fn test_fun2(y : &String, z : &Vec<f32>, r: &Root<isize>) -> () {
         let x = true;
         x
             && x;

python/tidy/servo_tidy_tests/test_tidy.py

@@ -123,6 +123,7 @@ class CheckTidiness(unittest.TestCase):
         self.assertEqual('use &[T] instead of &Vec<T>', errors.next()[2])
         self.assertEqual('use &str instead of &String', errors.next()[2])
         self.assertEqual('use &T instead of &Root<T>', errors.next()[2])
+        self.assertEqual('encountered function signature with -> ()', errors.next()[2])
         self.assertEqual('operators should go at the end of the first line', errors.next()[2])
         self.assertEqual('else braces should be on the same line', errors.next()[2])
         self.assertEqual('extra space after (', errors.next()[2])