Implementing `switch` expressions in `foundation/` and `material/` (#142279)

This PR is the fourth step in the journey to solve issue #136139 and make the entire Flutter repo more readable.

(previous pull requests: #139048, #139882, #141591)

This one is covering files in `packages/flutter/lib/src/foundation/` and `packages/flutter/lib/src/material/`.  
The `material/` directory is pretty big though, so for now I just did the files that start with `a`, `b`, and `c`.

packages/flutter/lib/src/foundation/binding.dart

@@ -585,14 +585,11 @@ abstract class BindingBase {
         name: FoundationServiceExtensions.brightnessOverride.name,
         callback: (Map<String, String> parameters) async {
           if (parameters.containsKey('value')) {
-            switch (parameters['value']) {
-              case 'Brightness.light':
-                debugBrightnessOverride = ui.Brightness.light;
-              case 'Brightness.dark':
-                debugBrightnessOverride = ui.Brightness.dark;
-              default:
-                debugBrightnessOverride = null;
-            }
+            debugBrightnessOverride = switch (parameters['value']) {
+              'Brightness.light' => ui.Brightness.light,
+              'Brightness.dark'  => ui.Brightness.dark,
+              _ => null,
+            };
             _postExtensionStateChangedEvent(
               FoundationServiceExtensions.brightnessOverride.name,
               (debugBrightnessOverride ?? platformDispatcher.platformBrightness).toString(),

packages/flutter/lib/src/foundation/diagnostics.dart

@@ -1718,34 +1718,23 @@ abstract class DiagnosticsNode {
   @protected
   TextTreeConfiguration? get textTreeConfiguration {
     assert(style != null);
-    switch (style!) {
-      case DiagnosticsTreeStyle.none:
-        return null;
-      case DiagnosticsTreeStyle.dense:
-        return denseTextConfiguration;
-      case DiagnosticsTreeStyle.sparse:
-        return sparseTextConfiguration;
-      case DiagnosticsTreeStyle.offstage:
-        return dashedTextConfiguration;
-      case DiagnosticsTreeStyle.whitespace:
-        return whitespaceTextConfiguration;
-      case DiagnosticsTreeStyle.transition:
-        return transitionTextConfiguration;
-      case DiagnosticsTreeStyle.singleLine:
-        return singleLineTextConfiguration;
-      case DiagnosticsTreeStyle.errorProperty:
-        return errorPropertyTextConfiguration;
-      case DiagnosticsTreeStyle.shallow:
-        return shallowTextConfiguration;
-      case DiagnosticsTreeStyle.error:
-        return errorTextConfiguration;
-      case DiagnosticsTreeStyle.truncateChildren:
-        // Truncate children doesn't really need its own text style as the
-        // rendering is quite custom.
-        return whitespaceTextConfiguration;
-      case DiagnosticsTreeStyle.flat:
-        return flatTextConfiguration;
-    }
+    return switch (style!) {
+      DiagnosticsTreeStyle.none          => null,
+      DiagnosticsTreeStyle.dense         => denseTextConfiguration,
+      DiagnosticsTreeStyle.sparse        => sparseTextConfiguration,
+      DiagnosticsTreeStyle.offstage      => dashedTextConfiguration,
+      DiagnosticsTreeStyle.whitespace    => whitespaceTextConfiguration,
+      DiagnosticsTreeStyle.transition    => transitionTextConfiguration,
+      DiagnosticsTreeStyle.singleLine    => singleLineTextConfiguration,
+      DiagnosticsTreeStyle.errorProperty => errorPropertyTextConfiguration,
+      DiagnosticsTreeStyle.shallow       => shallowTextConfiguration,
+      DiagnosticsTreeStyle.error         => errorTextConfiguration,
+      DiagnosticsTreeStyle.flat          => flatTextConfiguration,
+
+      // Truncate children doesn't really need its own text style as the
+      // rendering is quite custom.
+      DiagnosticsTreeStyle.truncateChildren => whitespaceTextConfiguration,
+    };
   }
 
   /// Returns a string representation of this node and its descendants.

packages/flutter/lib/src/material/about.dart

@@ -1187,15 +1187,10 @@ class _MasterDetailFlowState extends State<_MasterDetailFlow> implements _PageOp
         key: _navigatorKey,
         initialRoute: 'initial',
         onGenerateInitialRoutes: (NavigatorState navigator, String initialRoute) {
-          switch (focus) {
-            case _Focus.master:
-              return <Route<void>>[masterPageRoute];
-            case _Focus.detail:
-              return <Route<void>>[
-                masterPageRoute,
-                _detailPageRoute(_cachedDetailArguments),
-              ];
-          }
+          return switch (focus) {
+            _Focus.master => <Route<void>>[masterPageRoute],
+            _Focus.detail => <Route<void>>[masterPageRoute, _detailPageRoute(_cachedDetailArguments)],
+          };
         },
         onGenerateRoute: (RouteSettings settings) {
           switch (settings.name) {

packages/flutter/lib/src/material/adaptive_text_selection_toolbar.dart

@@ -212,28 +212,18 @@ class AdaptiveTextSelectionToolbar extends StatelessWidget {
       case TargetPlatform.windows:
         assert(debugCheckHasMaterialLocalizations(context));
         final MaterialLocalizations localizations = MaterialLocalizations.of(context);
-        switch (buttonItem.type) {
-          case ContextMenuButtonType.cut:
-            return localizations.cutButtonLabel;
-          case ContextMenuButtonType.copy:
-            return localizations.copyButtonLabel;
-          case ContextMenuButtonType.paste:
-            return localizations.pasteButtonLabel;
-          case ContextMenuButtonType.selectAll:
-            return localizations.selectAllButtonLabel;
-          case ContextMenuButtonType.delete:
-            return localizations.deleteButtonTooltip.toUpperCase();
-          case ContextMenuButtonType.lookUp:
-            return localizations.lookUpButtonLabel;
-          case ContextMenuButtonType.searchWeb:
-            return localizations.searchWebButtonLabel;
-          case ContextMenuButtonType.share:
-            return localizations.shareButtonLabel;
-          case ContextMenuButtonType.liveTextInput:
-            return localizations.scanTextButtonLabel;
-          case ContextMenuButtonType.custom:
-            return '';
-        }
+        return switch (buttonItem.type) {
+          ContextMenuButtonType.cut       => localizations.cutButtonLabel,
+          ContextMenuButtonType.copy      => localizations.copyButtonLabel,
+          ContextMenuButtonType.paste     => localizations.pasteButtonLabel,
+          ContextMenuButtonType.selectAll => localizations.selectAllButtonLabel,
+          ContextMenuButtonType.delete    => localizations.deleteButtonTooltip.toUpperCase(),
+          ContextMenuButtonType.lookUp    => localizations.lookUpButtonLabel,
+          ContextMenuButtonType.searchWeb => localizations.searchWebButtonLabel,
+          ContextMenuButtonType.share     => localizations.shareButtonLabel,
+          ContextMenuButtonType.liveTextInput => localizations.scanTextButtonLabel,
+          ContextMenuButtonType.custom => '',
+        };
     }
   }
 

packages/flutter/lib/src/material/arc.dart

@@ -279,12 +279,12 @@ class MaterialRectArcTween extends RectTween {
   }
 
   Offset _cornerFor(Rect rect, _CornerId id) {
-    switch (id) {
-      case _CornerId.topLeft: return rect.topLeft;
-      case _CornerId.topRight: return rect.topRight;
-      case _CornerId.bottomLeft: return rect.bottomLeft;
-      case _CornerId.bottomRight: return rect.bottomRight;
-    }
+    return switch (id) {
+      _CornerId.topLeft     => rect.topLeft,
+      _CornerId.topRight    => rect.topRight,
+      _CornerId.bottomLeft  => rect.bottomLeft,
+      _CornerId.bottomRight => rect.bottomRight,
+    };
   }
 
   /// The path of the corresponding [begin], [end] rectangle corners that lead

packages/flutter/lib/src/material/bottom_navigation_bar.dart

@@ -558,12 +558,10 @@ class _BottomNavigationTile extends StatelessWidget {
       ).evaluate(animation);
     }
 
-    switch (type) {
-      case BottomNavigationBarType.fixed:
-        size = 1;
-      case BottomNavigationBarType.shifting:
-        size = (flex! * 1000.0).round();
-    }
+    size = switch (type) {
+      BottomNavigationBarType.fixed => 1,
+      BottomNavigationBarType.shifting => (flex! * 1000.0).round(),
+    };
 
     Widget result = InkResponse(
       onTap: onTap,
@@ -858,12 +856,10 @@ class _BottomNavigationBarState extends State<BottomNavigationBar> with TickerPr
   // Unselected labels are shown by default for [BottomNavigationBarType.fixed],
   // and hidden by default for [BottomNavigationBarType.shifting].
   bool get _defaultShowUnselected {
-    switch (_effectiveType) {
-      case BottomNavigationBarType.shifting:
-        return false;
-      case BottomNavigationBarType.fixed:
-        return true;
-    }
+    return switch (_effectiveType) {
+      BottomNavigationBarType.shifting => false,
+      BottomNavigationBarType.fixed    => true,
+    };
   }
 
   @override
@@ -969,13 +965,10 @@ class _BottomNavigationBarState extends State<BottomNavigationBar> with TickerPr
     final ThemeData themeData = Theme.of(context);
     final BottomNavigationBarThemeData bottomTheme = BottomNavigationBarTheme.of(context);
 
-    final Color themeColor;
-    switch (themeData.brightness) {
-      case Brightness.light:
-        themeColor = themeData.colorScheme.primary;
-      case Brightness.dark:
-        themeColor = themeData.colorScheme.secondary;
-    }
+    final Color themeColor = switch (themeData.brightness) {
+      Brightness.light => themeData.colorScheme.primary,
+      Brightness.dark  => themeData.colorScheme.secondary,
+    };
 
     final TextStyle effectiveSelectedLabelStyle =
       _effectiveTextStyle(
@@ -1138,13 +1131,10 @@ class _BottomNavigationBarState extends State<BottomNavigationBar> with TickerPr
       ?? BottomNavigationBarLandscapeLayout.spread;
     final double additionalBottomPadding = MediaQuery.viewPaddingOf(context).bottom;
 
-    Color? backgroundColor;
-    switch (_effectiveType) {
-      case BottomNavigationBarType.fixed:
-        backgroundColor = widget.backgroundColor ?? bottomTheme.backgroundColor;
-      case BottomNavigationBarType.shifting:
-        backgroundColor = _backgroundColor;
-    }
+    final Color? backgroundColor = switch (_effectiveType) {
+      BottomNavigationBarType.fixed    => widget.backgroundColor ?? bottomTheme.backgroundColor,
+      BottomNavigationBarType.shifting => _backgroundColor,
+    };
 
     return Semantics(
       explicitChildNodes: true,
@@ -1298,8 +1288,8 @@ class _RadialPainter extends CustomPainter {
     for (int i = 0; i < circles.length; i += 1) {
       if (circles[i] != oldPainter.circles[i]) {
         return true;
-    }
       }
+    }
     return false;
   }
 
@@ -1309,13 +1299,10 @@ class _RadialPainter extends CustomPainter {
       final Paint paint = Paint()..color = circle.color;
       final Rect rect = Rect.fromLTWH(0.0, 0.0, size.width, size.height);
       canvas.clipRect(rect);
-      final double leftFraction;
-      switch (textDirection) {
-        case TextDirection.rtl:
-          leftFraction = 1.0 - circle.horizontalLeadingOffset;
-        case TextDirection.ltr:
-          leftFraction = circle.horizontalLeadingOffset;
-      }
+      final double leftFraction = switch (textDirection) {
+        TextDirection.rtl => 1.0 - circle.horizontalLeadingOffset,
+        TextDirection.ltr => circle.horizontalLeadingOffset,
+      };
       final Offset center = Offset(leftFraction * size.width, size.height / 2.0);
       final Tween<double> radiusTween = Tween<double>(
         begin: 0.0,

packages/flutter/lib/src/material/button_bar.dart

@@ -383,14 +383,11 @@ class _RenderButtonBarRow extends RenderFlex {
       super.performLayout();
     } else {
       final BoxConstraints childConstraints = constraints.copyWith(minWidth: 0.0);
-      RenderBox? child;
       double currentHeight = 0.0;
-      switch (verticalDirection) {
-        case VerticalDirection.down:
-          child = firstChild;
-        case VerticalDirection.up:
-          child = lastChild;
-      }
+      RenderBox? child = switch (verticalDirection) {
+        VerticalDirection.down => firstChild,
+        VerticalDirection.up   => lastChild,
+      };
 
       while (child != null) {
         final FlexParentData childParentData = child.parentData! as FlexParentData;

packages/flutter/lib/src/material/button_theme.dart

@@ -241,16 +241,11 @@ class ButtonThemeData with Diagnosticable {
   ///  * [getPadding], which is used to calculate padding for the [button]'s
   ///    child (typically the button's label).
   EdgeInsetsGeometry get padding {
-    if (_padding != null) {
-      return _padding;
-    }
-    switch (textTheme) {
-      case ButtonTextTheme.normal:
-      case ButtonTextTheme.accent:
-        return const EdgeInsets.symmetric(horizontal: 16.0);
-      case ButtonTextTheme.primary:
-        return const EdgeInsets.symmetric(horizontal: 24.0);
-    }
+    return _padding ?? switch (textTheme) {
+      ButtonTextTheme.normal  => const EdgeInsets.symmetric(horizontal: 16.0),
+      ButtonTextTheme.accent  => const EdgeInsets.symmetric(horizontal: 16.0),
+      ButtonTextTheme.primary => const EdgeInsets.symmetric(horizontal: 24.0),
+    };
   }
   final EdgeInsetsGeometry? _padding;
 
@@ -269,20 +264,12 @@ class ButtonThemeData with Diagnosticable {
   ///  * [getShape], which is used to calculate the shape of the [button]'s
   ///    [Material].
   ShapeBorder get shape {
-    if (_shape != null) {
-      return _shape;
-    }
-    switch (textTheme) {
-      case ButtonTextTheme.normal:
-      case ButtonTextTheme.accent:
-        return const RoundedRectangleBorder(
-          borderRadius: BorderRadius.all(Radius.circular(2.0)),
-        );
-      case ButtonTextTheme.primary:
-        return const RoundedRectangleBorder(
-          borderRadius: BorderRadius.all(Radius.circular(4.0)),
-        );
-    }
+    return _shape ?? switch (textTheme) {
+      ButtonTextTheme.normal || ButtonTextTheme.accent =>
+        const RoundedRectangleBorder(borderRadius: BorderRadius.all(Radius.circular(2.0))),
+      ButtonTextTheme.primary =>
+        const RoundedRectangleBorder(borderRadius: BorderRadius.all(Radius.circular(4.0))),
+    };
   }
   final ShapeBorder? _shape;
 

packages/flutter/lib/src/material/checkbox.dart

@@ -508,13 +508,10 @@ class _CheckboxState extends State<Checkbox> with TickerProviderStateMixin, Togg
     final VisualDensity effectiveVisualDensity = widget.visualDensity
       ?? checkboxTheme.visualDensity
       ?? defaults.visualDensity!;
-    Size size;
-    switch (effectiveMaterialTapTargetSize) {
-      case MaterialTapTargetSize.padded:
-        size = const Size(kMinInteractiveDimension, kMinInteractiveDimension);
-      case MaterialTapTargetSize.shrinkWrap:
-        size = const Size(kMinInteractiveDimension - 8.0, kMinInteractiveDimension - 8.0);
-    }
+    Size size = switch (effectiveMaterialTapTargetSize) {
+      MaterialTapTargetSize.padded     => const Size(kMinInteractiveDimension,       kMinInteractiveDimension),
+      MaterialTapTargetSize.shrinkWrap => const Size(kMinInteractiveDimension - 8.0, kMinInteractiveDimension - 8.0),
+    };
     size += effectiveVisualDensity.baseSizeAdjustment;
 
     final MaterialStateProperty<MouseCursor> effectiveMouseCursor = MaterialStateProperty.resolveWith<MouseCursor>((Set<MaterialState> states) {

packages/flutter/lib/src/material/chip.dart

@@ -1439,14 +1439,11 @@ class _ChipRenderWidget extends SlottedMultiChildRenderObjectWidget<_ChipSlot, R
 
   @override
   Widget? childForSlot(_ChipSlot slot) {
-    switch (slot) {
-      case _ChipSlot.label:
-        return theme.label;
-      case _ChipSlot.avatar:
-        return theme.avatar;
-      case _ChipSlot.deleteIcon:
-        return theme.deleteIcon;
-    }
+    return switch (slot) {
+      _ChipSlot.label      => theme.label,
+      _ChipSlot.avatar     => theme.avatar,
+      _ChipSlot.deleteIcon => theme.deleteIcon,
+    };
   }
 
   @override
@@ -1971,17 +1968,12 @@ class _RenderChip extends RenderBox with SlottedContainerRenderObjectMixin<_Chip
   }
 
   void _paintCheck(Canvas canvas, Offset origin, double size) {
-    Color? paintColor;
-    if (theme.checkmarkColor != null) {
-      paintColor = theme.checkmarkColor;
-    } else {
-      switch (theme.brightness) {
-        case Brightness.light:
-          paintColor = theme.showAvatar ? Colors.white : Colors.black.withAlpha(_kCheckmarkAlpha);
-        case Brightness.dark:
-          paintColor = theme.showAvatar ? Colors.black : Colors.white.withAlpha(_kCheckmarkAlpha);
-      }
-    }
+    Color? paintColor = theme.checkmarkColor ?? switch ((theme.brightness, theme.showAvatar)) {
+      (Brightness.light, true ) => Colors.white,
+      (Brightness.light, false) => Colors.black.withAlpha(_kCheckmarkAlpha),
+      (Brightness.dark,  true ) => Colors.black,
+      (Brightness.dark,  false) => Colors.white.withAlpha(_kCheckmarkAlpha),
+    };
 
     final ColorTween fadeTween = ColorTween(begin: Colors.transparent, end: paintColor);
 
@@ -2260,12 +2252,10 @@ bool _hitIsOnDeleteIcon({
     deflatedSize.width * 0.499,
     math.min(labelPadding.resolve(textDirection).right + deleteButtonSize.width, 24.0 + deleteButtonSize.width / 2.0),
   );
-  switch (textDirection) {
-    case TextDirection.ltr:
-      return adjustedPosition.dx >= deflatedSize.width - accessibleDeleteButtonWidth;
-    case TextDirection.rtl:
-      return adjustedPosition.dx <= accessibleDeleteButtonWidth;
-  }
+  return switch (textDirection) {
+    TextDirection.ltr => adjustedPosition.dx >= deflatedSize.width - accessibleDeleteButtonWidth,
+    TextDirection.rtl => adjustedPosition.dx <= accessibleDeleteButtonWidth,
+  };
 }
 
 // BEGIN GENERATED TOKEN PROPERTIES - Chip

packages/flutter/lib/src/material/circle_avatar.dart

@@ -204,19 +204,15 @@ class CircleAvatar extends StatelessWidget {
     Color? effectiveBackgroundColor = backgroundColor
       ?? (theme.useMaterial3 ? theme.colorScheme.primaryContainer : null);
     if (effectiveBackgroundColor == null) {
-      switch (ThemeData.estimateBrightnessForColor(textStyle.color!)) {
-        case Brightness.dark:
-          effectiveBackgroundColor = theme.primaryColorLight;
-        case Brightness.light:
-          effectiveBackgroundColor = theme.primaryColorDark;
-      }
+      effectiveBackgroundColor = switch (ThemeData.estimateBrightnessForColor(textStyle.color!)) {
+        Brightness.dark  => theme.primaryColorLight,
+        Brightness.light => theme.primaryColorDark,
+      };
     } else if (effectiveForegroundColor == null) {
-      switch (ThemeData.estimateBrightnessForColor(backgroundColor!)) {
-        case Brightness.dark:
-          textStyle = textStyle.copyWith(color: theme.primaryColorLight);
-        case Brightness.light:
-          textStyle = textStyle.copyWith(color: theme.primaryColorDark);
-      }
+      textStyle = switch (ThemeData.estimateBrightnessForColor(backgroundColor!)) {
+        Brightness.dark  => textStyle.copyWith(color: theme.primaryColorLight),
+        Brightness.light => textStyle.copyWith(color: theme.primaryColorDark),
+      };
     }
     final double minDiameter = _minDiameter;
     final double maxDiameter = _maxDiameter;

packages/flutter/lib/src/material/color_scheme.dart

@@ -193,13 +193,10 @@ class ColorScheme with Diagnosticable {
     Color? scrim,
     Color? surfaceTint,
   }) {
-    final Scheme scheme;
-    switch (brightness) {
-      case Brightness.light:
-        scheme = Scheme.light(seedColor.value);
-      case Brightness.dark:
-        scheme = Scheme.dark(seedColor.value);
-    }
+    final Scheme scheme = switch (brightness) {
+      Brightness.light => Scheme.light(seedColor.value),
+      Brightness.dark  => Scheme.dark(seedColor.value),
+    };
     return ColorScheme(
       primary: primary ?? Color(scheme.primary),
       onPrimary: onPrimary ?? Color(scheme.onPrimary),
@@ -1073,13 +1070,10 @@ class ColorScheme with Diagnosticable {
     final List<int> scoredResults = Score.score(colorToCount, desired: 1);
     final ui.Color baseColor = Color(scoredResults.first);
 
-    final Scheme scheme;
-    switch (brightness) {
-      case Brightness.light:
-        scheme = Scheme.light(baseColor.value);
-      case Brightness.dark:
-        scheme = Scheme.dark(baseColor.value);
-    }
+    final Scheme scheme = switch (brightness) {
+      Brightness.light => Scheme.light(baseColor.value),
+      Brightness.dark  => Scheme.dark(baseColor.value),
+    };
 
     return ColorScheme(primary: primary ?? Color(scheme.primary),
       onPrimary: onPrimary ?? Color(scheme.onPrimary),