Implementing control flow collections (#146601)

This pull request aims for improved readability, based on issue #146600.

```dart
// before
Set<Color> _distinctVisibleColors() {
  final Set<Color> distinctVisibleColors = <Color>{};
  if (top.style != BorderStyle.none) {
    distinctVisibleColors.add(top.color);
  }
  if (right.style != BorderStyle.none) {
    distinctVisibleColors.add(right.color);
  }
  if (bottom.style != BorderStyle.none) {
    distinctVisibleColors.add(bottom.color);
  }
  if (left.style != BorderStyle.none) {
    distinctVisibleColors.add(left.color);
  }
  return distinctVisibleColors;
}

// after
Set<Color> _distinctVisibleColors() {
  return <Color>{
    if (top.style != BorderStyle.none) top.color,
    if (right.style != BorderStyle.none) right.color,
    if (bottom.style != BorderStyle.none) bottom.color,
    if (left.style != BorderStyle.none) left.color,
  };
}
```

Most of the repo should be covered in this PR (aside from `flutter_tools/`, since there was a lot going on in there).

dev/benchmarks/platform_channels_benchmarks/lib/main.dart

@@ -11,30 +11,20 @@ import 'package:flutter/services.dart';
 import 'package:microbenchmarks/common.dart';
 
 List<Object?> _makeTestBuffer(int size) {
-  final List<Object?> answer = <Object?>[];
-  for (int i = 0; i < size; ++i) {
-    switch (i % 9) {
-      case 0:
-        answer.add(1);
-      case 1:
-        answer.add(math.pow(2, 65));
-      case 2:
-        answer.add(1234.0);
-      case 3:
-        answer.add(null);
-      case 4:
-        answer.add(<int>[1234]);
-      case 5:
-        answer.add(<String, int>{'hello': 1234});
-      case 6:
-        answer.add('this is a test');
-      case 7:
-        answer.add(true);
-      case 8:
-        answer.add(Uint8List(64));
-    }
-  }
-  return answer;
+  return <Object?>[
+    for (int i = 0; i < size; i++)
+      switch (i % 9) {
+        0 => 1,
+        1 => math.pow(2, 65),
+        2 => 1234.0,
+        3 => null,
+        4 => <int>[1234],
+        5 => <String, int>{'hello': 1234},
+        6 => 'this is a test',
+        7 => true,
+        _ => Uint8List(64),
+      },
+  ];
 }
 
 Future<double> _runBasicStandardSmall(

dev/bots/suite_runners/run_verify_binaries_codesigned_tests.dart

@@ -139,28 +139,21 @@ Future<void> verifyExist(
   String flutterRoot,
   {@visibleForTesting ProcessManager processManager = const LocalProcessManager()
 }) async {
-  final Set<String> foundFiles = <String>{};
-  final String cacheDirectory =  path.join(flutterRoot, 'bin', 'cache');
-
-  for (final String binaryPath
-      in await findBinaryPaths(cacheDirectory, processManager: processManager)) {
-    if (binariesWithEntitlements(flutterRoot).contains(binaryPath)) {
-      foundFiles.add(binaryPath);
-    } else if (binariesWithoutEntitlements(flutterRoot).contains(binaryPath)) {
-      foundFiles.add(binaryPath);
-    } else {
-      throw Exception(
-          'Found unexpected binary in cache: $binaryPath');
-    }
-  }
-
+  final List<String> binaryPaths = await findBinaryPaths(
+    path.join(flutterRoot, 'bin', 'cache'),
+    processManager: processManager,
+  );
   final List<String> allExpectedFiles = binariesWithEntitlements(flutterRoot) + binariesWithoutEntitlements(flutterRoot);
+  final Set<String> foundFiles = <String>{
+    for (final String binaryPath in binaryPaths)
+      if (allExpectedFiles.contains(binaryPath)) binaryPath
+      else throw Exception('Found unexpected binary in cache: $binaryPath'),
+  };
+
   if (foundFiles.length < allExpectedFiles.length) {
-    final List<String> unfoundFiles = allExpectedFiles
-        .where(
-          (String file) => !foundFiles.contains(file),
-        )
-        .toList();
+    final List<String> unfoundFiles = <String>[
+      for (final String file in allExpectedFiles) if (!foundFiles.contains(file)) file,
+    ];
     print(
       'Expected binaries not found in cache:\n\n${unfoundFiles.join('\n')}\n\n'
       'If this commit is removing binaries from the cache, this test should be fixed by\n'

dev/bots/test.dart

@@ -913,18 +913,14 @@ Future<void> _runFrameworkTests() async {
         final Uint8List libappBytes = libapp.content as Uint8List; // bytes decompressed here
         final String libappStrings = utf8.decode(libappBytes, allowMalformed: true);
         await runCommand(flutter, <String>['clean'], workingDirectory: tracingDirectory);
-        final List<String> results = <String>[];
-        for (final String pattern in allowed) {
-          if (!libappStrings.contains(pattern)) {
-            results.add('When building with --$modeArgument, expected to find "$pattern" in libapp.so but could not find it.');
-          }
-        }
-        for (final String pattern in disallowed) {
-          if (libappStrings.contains(pattern)) {
-            results.add('When building with --$modeArgument, expected to not find "$pattern" in libapp.so but did find it.');
-          }
-        }
-        return results;
+        return <String>[
+          for (final String pattern in allowed)
+            if (!libappStrings.contains(pattern))
+              'When building with --$modeArgument, expected to find "$pattern" in libapp.so but could not find it.',
+          for (final String pattern in disallowed)
+            if (libappStrings.contains(pattern))
+              'When building with --$modeArgument, expected to not find "$pattern" in libapp.so but did find it.',
+        ];
       } catch (error, stackTrace) {
         return <String>[
           error.toString(),
@@ -1332,11 +1328,9 @@ Future<void> _runDartTest(String workingDirectory, {
 
   if (collectMetrics) {
     try {
-      final List<String> testList = <String>[];
-      final Map<int, TestSpecs> allTestSpecs = test.allTestSpecs;
-      for (final TestSpecs testSpecs in allTestSpecs.values) {
-        testList.add(testSpecs.toJson());
-      }
+      final List<String> testList = <String>[
+        for (final TestSpecs testSpecs in test.allTestSpecs.values) testSpecs.toJson(),
+      ];
       if (testList.isNotEmpty) {
         final String testJson = json.encode(testList);
         final File testResults = fileSystem.file(

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

@@ -110,12 +110,10 @@ class NextContext extends Context {
           break;
         }
 
-        final List<pb.Cherrypick> unappliedCherrypicks = <pb.Cherrypick>[];
-        for (final pb.Cherrypick cherrypick in state.engine.cherrypicks) {
-          if (!finishedStates.contains(cherrypick.state)) {
-            unappliedCherrypicks.add(cherrypick);
-          }
-        }
+        final List<pb.Cherrypick> unappliedCherrypicks = <pb.Cherrypick>[
+          for (final pb.Cherrypick cherrypick in state.engine.cherrypicks)
+            if (!finishedStates.contains(cherrypick.state)) cherrypick,
+        ];
 
         if (unappliedCherrypicks.isEmpty) {
           stdio.printStatus('All engine cherrypicks have been auto-applied by the conductor.\n');
@@ -206,12 +204,10 @@ class NextContext extends Context {
           );
         }
 
-        final List<pb.Cherrypick> unappliedCherrypicks = <pb.Cherrypick>[];
-        for (final pb.Cherrypick cherrypick in state.framework.cherrypicks) {
-          if (!finishedStates.contains(cherrypick.state)) {
-            unappliedCherrypicks.add(cherrypick);
-          }
-        }
+        final List<pb.Cherrypick> unappliedCherrypicks = <pb.Cherrypick>[
+          for (final pb.Cherrypick cherrypick in state.framework.cherrypicks)
+            if (!finishedStates.contains(cherrypick.state)) cherrypick,
+        ];
 
         if (state.framework.cherrypicks.isEmpty) {
           stdio.printStatus(

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

@@ -183,15 +183,11 @@ abstract class Repository {
       workingDirectory: (await checkoutDirectory).path,
     );
 
-    final List<String> remoteBranches = <String>[];
-    for (final String line in output.split('\n')) {
-      final RegExpMatch? match = _lsRemotePattern.firstMatch(line);
-      if (match != null) {
-        remoteBranches.add(match.group(1)!);
-      }
-    }
-
-    return remoteBranches;
+    return <String>[
+      for (final String line in output.split('\n'))
+        if (_lsRemotePattern.firstMatch(line) case final RegExpMatch match)
+          match.group(1)!,
+    ];
   }
 
   /// Ensure the repository is cloned to disk and initialized with proper state.

dev/devicelab/lib/tasks/microbenchmarks.dart

@@ -39,8 +39,8 @@ TaskFunction createMicrobenchmarkTask({
             if (enableImpeller != null && !enableImpeller) '--no-enable-impeller',
             '-d',
             device.deviceId,
+            benchmarkPath,
           ];
-          options.add(benchmarkPath);
           return startFlutter(
             'run',
             options: options,

dev/integration_tests/android_semantics_testing/lib/src/common.dart

@@ -154,14 +154,11 @@ class AndroidSemanticsNode {
     if (actions == null) {
       return const <AndroidSemanticsAction>[];
     }
-    final List<AndroidSemanticsAction> convertedActions = <AndroidSemanticsAction>[];
-    for (final int id in actions) {
-      final AndroidSemanticsAction? action = AndroidSemanticsAction.deserialize(id);
-      if (action != null) {
-        convertedActions.add(action);
-      }
-    }
-    return convertedActions;
+    return <AndroidSemanticsAction>[
+      for (final int id in actions)
+        if (AndroidSemanticsAction.deserialize(id) case final AndroidSemanticsAction action)
+          action,
+    ];
   }
 
   @override

dev/integration_tests/flutter_gallery/lib/demo/calculator/logic.dart

@@ -121,10 +121,8 @@ class CalcExpression {
     : this(<ExpressionToken>[], ExpressionState.Start);
 
   CalcExpression.result(FloatToken result)
-    : _list = <ExpressionToken?>[],
-      state = ExpressionState.Result {
-    _list.add(result);
-  }
+    : _list = <ExpressionToken?>[result],
+      state = ExpressionState.Result;
 
   /// The tokens comprising the expression.
   final List<ExpressionToken?> _list;

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

@@ -84,15 +84,11 @@ class _CupertinoSearchTextFieldDemoState
 
   Widget _buildPlatformList() {
     if (_searchPlatform.isNotEmpty) {
-      final List<String> tempList = <String>[];
-      for (int i = 0; i < filteredPlatforms.length; i++) {
-        if (filteredPlatforms[i]
-            .toLowerCase()
-            .contains(_searchPlatform.toLowerCase())) {
-          tempList.add(filteredPlatforms[i]);
-        }
-      }
-      filteredPlatforms = tempList;
+      final String search = _searchPlatform.toLowerCase();
+      filteredPlatforms = <String>[
+        for (final String platform in filteredPlatforms)
+          if (platform.toLowerCase().contains(search)) platform
+      ];
     }
     return ListView.builder(
       itemCount: filteredPlatforms.length,

dev/integration_tests/new_gallery/lib/demos/material/data_table_demo.dart

@@ -26,14 +26,10 @@ class _RestorableDessertSelections extends RestorableProperty<Set<int>> {
   /// Takes a list of [_Dessert]s and saves the row indices of selected rows
   /// into a [Set].
   void setDessertSelections(List<_Dessert> desserts) {
-    final Set<int> updatedSet = <int>{};
-    for (int i = 0; i < desserts.length; i += 1) {
-      final _Dessert dessert = desserts[i];
-      if (dessert.selected) {
-        updatedSet.add(i);
-      }
-    }
-    _dessertSelections = updatedSet;
+    _dessertSelections = <int>{
+      for (final (int i, _Dessert dessert) in desserts.indexed)
+        if (dessert.selected) i,
+    };
     notifyListeners();
   }
 

dev/tools/examples_smoke_test.dart

@@ -116,19 +116,18 @@ Future<File> generateTest(Directory apiDir) async {
   });
 
   // Collect the examples, and import them all as separate symbols.
-  final List<String> imports = <String>[];
-  imports.add('''import 'package:flutter/widgets.dart';''');
-  imports.add('''import 'package:flutter/scheduler.dart';''');
-  imports.add('''import 'package:flutter_test/flutter_test.dart';''');
-  imports.add('''import 'package:integration_test/integration_test.dart';''');
-  final List<ExampleInfo> infoList = <ExampleInfo>[];
-  for (final File example in examples) {
-    final ExampleInfo info = ExampleInfo(example, examplesLibDir);
-    infoList.add(info);
-    imports.add('''import 'package:flutter_api_samples/${info.importPath}' as ${info.importName};''');
-  }
-  imports.sort();
+  final List<ExampleInfo> infoList = <ExampleInfo>[
+    for (final File example in examples) ExampleInfo(example, examplesLibDir),
+  ];
   infoList.sort((ExampleInfo a, ExampleInfo b) => a.importPath.compareTo(b.importPath));
+  final List<String> imports = <String>[
+    "import 'package:flutter/widgets.dart';",
+    "import 'package:flutter/scheduler.dart';",
+    "import 'package:flutter_test/flutter_test.dart';",
+    "import 'package:integration_test/integration_test.dart';",
+    for (final ExampleInfo info in infoList)
+      "import 'package:flutter_api_samples/${info.importPath}' as ${info.importName};"
+  ]..sort();
 
   final StringBuffer buffer = StringBuffer();
   buffer.writeln('// Temporary generated file. Do not commit.');

dev/tools/update_icons.dart

@@ -388,15 +388,10 @@ bool testIsSuperset(Map<String, String> newCodepoints, Map<String, String> oldCo
 @visibleForTesting
 bool testIsStable(Map<String, String> newCodepoints, Map<String, String> oldCodepoints) {
   final int oldCodepointsCount = oldCodepoints.length;
-  final List<String> unstable = <String>[];
-
-  oldCodepoints.forEach((String key, String value) {
-    if (newCodepoints.containsKey(key)) {
-      if (value != newCodepoints[key]) {
-        unstable.add(key);
-      }
-    }
-  });
+  final List<String> unstable = <String>[
+    for (final MapEntry<String, String>(:String key, :String value) in oldCodepoints.entries)
+      if (newCodepoints.containsKey(key) && value != newCodepoints[key]) key,
+  ];
 
   if (unstable.isNotEmpty) {
     stderr.writeln('❌ out of $oldCodepointsCount existing codepoints, ${unstable.length} were unstable: $unstable');

packages/flutter/lib/src/cupertino/dialog.dart

@@ -1485,22 +1485,15 @@ class _CupertinoAlertActionSection extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-
-    final List<Widget> interactiveButtons = <Widget>[];
-    for (int i = 0; i < children.length; i += 1) {
-      interactiveButtons.add(
-        _PressableActionButton(
-          child: children[i],
-        ),
-      );
-    }
-
     return CupertinoScrollbar(
       controller: scrollController,
       child: SingleChildScrollView(
         controller: scrollController,
         child: _CupertinoDialogActionsRenderWidget(
-          actionButtons: interactiveButtons,
+          actionButtons: <Widget>[
+            for (final Widget child in children)
+              _PressableActionButton(child: child),
+          ],
           dividerThickness: _kDividerThickness,
           hasCancelButton: hasCancelButton,
           isActionSheet: isActionSheet,

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

@@ -311,12 +311,10 @@ final class _Float64ListChain {
   /// are read back, they do not affect the timings of the work being
   /// benchmarked.
   List<double> extractElements() {
-    final List<double> result = <double>[];
-    _chain.forEach(result.addAll);
-    for (int i = 0; i < _pointer; i++) {
-      result.add(_slice[i]);
-    }
-    return result;
+    return <double>[
+      for (final Float64List list in _chain) ...list,
+      for (int i = 0; i < _pointer; i++) _slice[i],
+    ];
   }
 }
 
@@ -349,16 +347,11 @@ final class _StringListChain {
   /// are read back, they do not affect the timings of the work being
   /// benchmarked.
   List<String> extractElements() {
-    final List<String> result = <String>[];
-    for (final List<String?> slice in _chain) {
-      for (final String? element in slice) {
-        result.add(element!);
-      }
-    }
-    for (int i = 0; i < _pointer; i++) {
-      result.add(_slice[i]!);
-    }
-    return result;
+    return <String>[
+      for (final List<String?> slice in _chain)
+        for (final String? value in slice) value!,
+      for (int i = 0; i < _pointer; i++) _slice[i]!,
+    ];
   }
 }