switch statement cleanup (#148382)

This PR is step 12 in the journey to solve issue #136139 and make the
entire Flutter repo more readable.

Most of it involves implementing switch expressions, and there's also a
few other random things that I wanted to clean up a bit.

Author: nate-thegrate

dev/bots/analyze_snippet_code.dart

@@ -1187,10 +1187,8 @@ Future<void> _runInteractive({
       case 'q':
         checker.cleanupTempDirectory();
         exit(0);
-      case 'r':
-        if (!busy) {
-          rerun();
-        }
+      case 'r' when !busy:
+        rerun();
     }
   });
   Watcher(file.absolute.path).events.listen((_) => rerun());

dev/conductor/core/lib/src/start.dart

@@ -385,23 +385,12 @@ class StartContext extends Context {
 
   /// Determine this release's version number from the [lastVersion] and the [incrementLetter].
   Version calculateNextVersion(Version lastVersion, ReleaseType releaseType) {
-    late final Version nextVersion;
-    switch (releaseType) {
-      case ReleaseType.STABLE_INITIAL:
-        nextVersion = Version(
-          x: lastVersion.x,
-          y: lastVersion.y,
-          z: 0,
-          type: VersionType.stable,
-        );
-      case ReleaseType.STABLE_HOTFIX:
-        nextVersion = Version.increment(lastVersion, 'z');
-      case ReleaseType.BETA_INITIAL:
-        nextVersion = Version.fromCandidateBranch(candidateBranch);
-      case ReleaseType.BETA_HOTFIX:
-        nextVersion = Version.increment(lastVersion, 'n');
-    }
-    return nextVersion;
+    return switch (releaseType) {
+      ReleaseType.STABLE_INITIAL   => Version(x: lastVersion.x, y: lastVersion.y, z: 0, type: VersionType.stable),
+      ReleaseType.STABLE_HOTFIX    => Version.increment(lastVersion, 'z'),
+      ReleaseType.BETA_INITIAL     => Version.fromCandidateBranch(candidateBranch),
+      ReleaseType.BETA_HOTFIX || _ => Version.increment(lastVersion, 'n'),
+    };
   }
 
   /// Ensures the branch point [candidateBranch] and `master` has a version tag.

dev/devicelab/lib/framework/ab.dart

@@ -115,15 +115,11 @@ class ABTest {
       if (value == null) {
         value = ''.padRight(len);
       } else {
-        switch (aligns[column]) {
-          case FieldJustification.LEFT:
-            value = value.padRight(len);
-          case FieldJustification.RIGHT:
-            value = value.padLeft(len);
-          case FieldJustification.CENTER:
-            value = value.padLeft((len + value.length) ~/2);
-            value = value.padRight(len);
-        }
+        value = switch (aligns[column]) {
+          FieldJustification.LEFT   => value.padRight(len),
+          FieldJustification.RIGHT  => value.padLeft(len),
+          FieldJustification.CENTER => value.padLeft((len + value.length) ~/ 2).padRight(len),
+        };
       }
       if (column > 0) {
         value = value.padLeft(len+1);

dev/devicelab/lib/framework/devices.dart

@@ -252,14 +252,11 @@ class AndroidDeviceDiscovery implements DeviceDiscovery {
   }
 
   Future<bool> _matchesCPURequirement(AndroidDevice device) async {
-    switch (cpu) {
-      case null:
-        return true;
-      case AndroidCPU.arm64:
-        return device.isArm64();
-      case AndroidCPU.arm:
-        return device.isArm();
-    }
+    return switch (cpu) {
+      null => Future<bool>.value(true),
+      AndroidCPU.arm64 => device.isArm64(),
+      AndroidCPU.arm   => device.isArm(),
+    };
   }
 
   /// Picks a random Android device out of connected devices and sets it as

dev/integration_tests/channels/lib/src/test_step.dart

@@ -37,19 +37,12 @@ class TestStepResult {
   });
 
   factory TestStepResult.fromSnapshot(AsyncSnapshot<TestStepResult> snapshot) {
-    switch (snapshot.connectionState) {
-      case ConnectionState.none:
-        return const TestStepResult('Not started', nothing, TestStatus.ok);
-      case ConnectionState.waiting:
-        return const TestStepResult('Executing', nothing, TestStatus.pending);
-      case ConnectionState.done:
-        if (snapshot.hasData) {
-          return snapshot.data!;
-        }
-        return snapshot.error! as TestStepResult;
-      case ConnectionState.active:
-        throw 'Unsupported state ${snapshot.connectionState}';
-    }
+    return switch (snapshot.connectionState) {
+      ConnectionState.none    => const TestStepResult('Not started', nothing, TestStatus.ok),
+      ConnectionState.waiting => const TestStepResult('Executing', nothing, TestStatus.pending),
+      ConnectionState.done    => snapshot.data ?? snapshot.error! as TestStepResult,
+      ConnectionState.active  => throw 'Unsupported state: ConnectionState.active',
+    };
   }
 
   final String name;

dev/integration_tests/flutter_gallery/lib/demo/material/list_demo.dart

@@ -204,18 +204,12 @@ class _ListDemoState extends State<ListDemo> {
   @override
   Widget build(BuildContext context) {
     final String layoutText = _dense != null ? ' \u2013 Dense' : '';
-    String? itemTypeText;
-    switch (_itemType) {
-      case _MaterialListType.oneLine:
-      case _MaterialListType.oneLineWithAvatar:
-        itemTypeText = 'Single-line';
-      case _MaterialListType.twoLine:
-        itemTypeText = 'Two-line';
-      case _MaterialListType.threeLine:
-        itemTypeText = 'Three-line';
-      case null:
-        break;
-    }
+    final String? itemTypeText = switch (_itemType) {
+      _MaterialListType.oneLine || _MaterialListType.oneLineWithAvatar => 'Single-line',
+      _MaterialListType.twoLine => 'Two-line',
+      _MaterialListType.threeLine => 'Three-line',
+      null => null,
+    };
 
     Iterable<Widget> listTiles = items.map<Widget>((String item) => buildListTile(context, item));
     if (_showDividers != null) {

dev/integration_tests/flutter_gallery/lib/demo/material/slider_demo.dart

@@ -80,29 +80,12 @@ class _CustomRangeThumbShape extends RangeSliderThumbShape {
     );
 
     final double size = _thumbSize * sizeTween.evaluate(enableAnimation);
-    late Path thumbPath;
-    switch (textDirection) {
-      case TextDirection.rtl:
-        switch (thumb) {
-          case Thumb.start:
-            thumbPath = _rightTriangle(size, center);
-          case Thumb.end:
-            thumbPath = _leftTriangle(size, center);
-          case null:
-            break;
-        }
-      case TextDirection.ltr:
-        switch (thumb) {
-          case Thumb.start:
-            thumbPath = _leftTriangle(size, center);
-          case Thumb.end:
-            thumbPath = _rightTriangle(size, center);
-          case null:
-            break;
-        }
-      case null:
-        break;
-    }
+    final Path thumbPath = switch ((textDirection!, thumb!)) {
+      (TextDirection.rtl, Thumb.start) => _rightTriangle(size, center),
+      (TextDirection.rtl, Thumb.end)   => _leftTriangle(size, center),
+      (TextDirection.ltr, Thumb.start) => _leftTriangle(size, center),
+      (TextDirection.ltr, Thumb.end)   => _rightTriangle(size, center),
+    };
     canvas.drawPath(thumbPath, Paint()..color = colorTween.evaluate(enableAnimation)!);
   }
 }

dev/integration_tests/new_gallery/lib/data/demos.dart

@@ -50,15 +50,11 @@ enum GalleryDemoCategory {
   }
 
   String? displayTitle(GalleryLocalizations localizations) {
-    switch (this) {
-      case GalleryDemoCategory.other:
-        return localizations.homeCategoryReference;
-      case GalleryDemoCategory.material:
-      case GalleryDemoCategory.cupertino:
-        return toString();
-      case GalleryDemoCategory.study:
-    }
-    return null;
+    return switch (this) {
+      study => null,
+      material || cupertino => toString(),
+      other => localizations.homeCategoryReference,
+    };
   }
 }
 

dev/integration_tests/new_gallery/lib/data/gallery_options.dart

@@ -96,22 +96,15 @@ class GalleryOptions {
   /// In other words, if the theme is dark, returns light; if the theme is
   /// light, returns dark.
   SystemUiOverlayStyle resolvedSystemUiOverlayStyle() {
-    Brightness brightness;
-    switch (themeMode) {
-      case ThemeMode.light:
-        brightness = Brightness.light;
-      case ThemeMode.dark:
-        brightness = Brightness.dark;
-      case ThemeMode.system:
-        brightness =
-            WidgetsBinding.instance.platformDispatcher.platformBrightness;
-    }
-
-    final SystemUiOverlayStyle overlayStyle = brightness == Brightness.dark
-        ? SystemUiOverlayStyle.light
-        : SystemUiOverlayStyle.dark;
-
-    return overlayStyle;
+    final Brightness brightness = switch (themeMode) {
+      ThemeMode.light  => Brightness.light,
+      ThemeMode.dark   => Brightness.dark,
+      ThemeMode.system => WidgetsBinding.instance.platformDispatcher.platformBrightness,
+    };
+    return switch (brightness) {
+      Brightness.light => SystemUiOverlayStyle.dark,
+      Brightness.dark  => SystemUiOverlayStyle.light,
+    };
   }
 
   GalleryOptions copyWith({

dev/integration_tests/new_gallery/lib/demos/cupertino/cupertino_alert_demo.dart

@@ -105,18 +105,13 @@ class _CupertinoAlertDemoState extends State<CupertinoAlertDemo>
 
   String _title(BuildContext context) {
     final GalleryLocalizations localizations = GalleryLocalizations.of(context)!;
-    switch (widget.type) {
-      case AlertDemoType.alert:
-        return localizations.demoCupertinoAlertTitle;
-      case AlertDemoType.alertTitle:
-        return localizations.demoCupertinoAlertWithTitleTitle;
-      case AlertDemoType.alertButtons:
-        return localizations.demoCupertinoAlertButtonsTitle;
-      case AlertDemoType.alertButtonsOnly:
-        return localizations.demoCupertinoAlertButtonsOnlyTitle;
-      case AlertDemoType.actionSheet:
-        return localizations.demoCupertinoActionSheetTitle;
-    }
+    return switch (widget.type) {
+      AlertDemoType.alert            => localizations.demoCupertinoAlertTitle,
+      AlertDemoType.alertTitle       => localizations.demoCupertinoAlertWithTitleTitle,
+      AlertDemoType.alertButtons     => localizations.demoCupertinoAlertButtonsTitle,
+      AlertDemoType.alertButtonsOnly => localizations.demoCupertinoAlertButtonsOnlyTitle,
+      AlertDemoType.actionSheet      => localizations.demoCupertinoActionSheetTitle,
+    };
   }
 
   static Route<String> _alertDemoDialog(