Style: forbid .zip and .chain (#8188)

The `zip(a, b)` variant produces clearer code imho.

Downside: added dependency on `itertools`

crates/egui/Cargo.toml

@@ -74,6 +74,7 @@ epaint = { workspace = true, default-features = false }
 accesskit.workspace = true
 ahash.workspace = true
 bitflags.workspace = true
+itertools.workspace = true
 log.workspace = true
 nohash-hasher.workspace = true
 profiling.workspace = true

crates/egui/src/containers/popup.rs

@@ -472,17 +472,15 @@ impl<'a> Popup<'a> {
         RectAlign::find_best_align(
             #[expect(clippy::iter_on_empty_collections)]
             #[expect(clippy::or_fun_call)]
-            once(self.rect_align).chain(
+            std::iter::chain(
+                once(self.rect_align),
                 self.alternative_aligns
                     // Need the empty slice so the iters have the same type so we can unwrap_or
-                    .map(|a| a.iter().copied().chain([].iter().copied()))
-                    .unwrap_or(
-                        self.rect_align
-                            .symmetries()
-                            .iter()
-                            .copied()
-                            .chain(RectAlign::MENU_ALIGNS.iter().copied()),
-                    ),
+                    .map(|a| std::iter::chain(a.iter().copied(), [].iter().copied()))
+                    .unwrap_or(std::iter::chain(
+                        self.rect_align.symmetries().iter().copied(),
+                        RectAlign::MENU_ALIGNS.iter().copied(),
+                    )),
             ),
             self.ctx.content_rect(),
             anchor_rect,

crates/egui/src/context.rs

@@ -641,11 +641,7 @@ impl ContextImpl {
     }
 
     fn all_viewport_ids(&self) -> ViewportIdSet {
-        self.viewports
-            .keys()
-            .copied()
-            .chain([ViewportId::ROOT])
-            .collect()
+        std::iter::chain(self.viewports.keys().copied(), [ViewportId::ROOT]).collect()
     }
 
     /// The current active viewport

crates/egui/src/interaction.rs

@@ -232,20 +232,14 @@ pub(crate) fn interact(
     //     );
     // }
 
-    let contains_pointer: IdSet = hits
-        .contains_pointer
-        .iter()
-        .chain(&hits.click)
-        .chain(&hits.drag)
-        .map(|w| w.id)
-        .collect();
+    let contains_pointer: IdSet =
+        itertools::chain!(&hits.contains_pointer, &hits.click, &hits.drag)
+            .map(|w| w.id)
+            .collect();
 
     let hovered = if clicked.is_some() || dragged.is_some() || long_touched.is_some() {
         // If currently clicking or dragging, only that and nothing else is hovered.
-        clicked
-            .iter()
-            .chain(&dragged)
-            .chain(&long_touched)
+        itertools::chain!(&clicked, &dragged, &long_touched)
             .copied()
             .collect()
     } else {
@@ -268,7 +262,9 @@ pub(crate) fn interact(
         let drag_order = hits.drag.and_then(|w| order(w.id)).unwrap_or(0);
         let top_interactive_order = click_order.max(drag_order);
 
-        let mut hovered: IdSet = hits.click.iter().chain(&hits.drag).map(|w| w.id).collect();
+        let mut hovered: IdSet = std::iter::chain(&hits.click, &hits.drag)
+            .map(|w| w.id)
+            .collect();
 
         for w in &hits.contains_pointer {
             let is_interactive = w.sense.senses_click() || w.sense.senses_drag();

crates/egui/src/memory/mod.rs

@@ -1232,11 +1232,12 @@ impl Areas {
     }
 
     pub fn visible_layer_ids(&self) -> ahash::HashSet<LayerId> {
-        self.visible_areas_last_frame
-            .iter()
-            .copied()
-            .chain(self.visible_areas_current_frame.iter().copied())
-            .collect()
+        std::iter::chain(
+            &self.visible_areas_last_frame,
+            &self.visible_areas_current_frame,
+        )
+        .copied()
+        .collect()
     }
 
     pub(crate) fn visible_windows(&self) -> impl Iterator<Item = (LayerId, &area::AreaState)> {