prefer_initializing_formals (#8797)

dev/manual_tests/material_arc.dart

@@ -393,10 +393,9 @@ class _RectangleDemoState extends State<_RectangleDemo> {
 typedef Widget _DemoBuilder(_ArcDemo demo);
 
 class _ArcDemo {
-  _ArcDemo(String _title, this.builder, TickerProvider vsync)
-    : title = _title,
-      controller = new AnimationController(duration: const Duration(milliseconds: 500), vsync: vsync),
-      key = new GlobalKey(debugLabel: _title);
+  _ArcDemo(this.title, this.builder, TickerProvider vsync)
+    : controller = new AnimationController(duration: const Duration(milliseconds: 500), vsync: vsync),
+      key = new GlobalKey(debugLabel: title);
 
   final String title;
   final _DemoBuilder builder;

examples/flutter_gallery/lib/demo/calculator/logic.dart

@@ -66,9 +66,8 @@ enum Operation { Addition, Subtraction, Multiplication, Division }
 
 /// A token that represents an arithmetic operation symbol.
 class OperationToken extends ExpressionToken {
-  OperationToken(Operation operation)
-   : operation = operation,
-     super(opString(operation));
+  OperationToken(this.operation)
+   : super(opString(operation));
 
   Operation operation;
 

examples/layers/rendering/src/sector_layout.dart

@@ -548,11 +548,10 @@ class RenderBoxToRenderSectorAdapter extends RenderBox with RenderObjectWithChil
 }
 
 class RenderSolidColor extends RenderDecoratedSector {
-  RenderSolidColor(Color backgroundColor, {
+  RenderSolidColor(this.backgroundColor, {
     this.desiredDeltaRadius: double.INFINITY,
     this.desiredDeltaTheta: kTwoPi
-  }) : this.backgroundColor = backgroundColor,
-       super(new BoxDecoration(backgroundColor: backgroundColor));
+  }) : super(new BoxDecoration(backgroundColor: backgroundColor));
 
   double desiredDeltaRadius;
   double desiredDeltaTheta;

examples/layers/rendering/src/solid_color_box.dart

@@ -9,9 +9,8 @@ class RenderSolidColorBox extends RenderDecoratedBox {
   final Size desiredSize;
   final Color backgroundColor;
 
-  RenderSolidColorBox(Color backgroundColor, { this.desiredSize: Size.infinite })
-      : backgroundColor = backgroundColor,
-        super(decoration: new BoxDecoration(backgroundColor: backgroundColor));
+  RenderSolidColorBox(this.backgroundColor, { this.desiredSize: Size.infinite })
+      : super(decoration: new BoxDecoration(backgroundColor: backgroundColor));
 
   @override
   double computeMinIntrinsicWidth(double height) {

examples/stocks/lib/stock_row.dart

@@ -11,11 +11,11 @@ typedef void StockRowActionCallback(Stock stock);
 
 class StockRow extends StatelessWidget {
   StockRow({
-    Stock stock,
+    this.stock,
     this.onPressed,
     this.onDoubleTap,
     this.onLongPressed
-  }) : this.stock = stock, super(key: new ObjectKey(stock));
+  }) : super(key: new ObjectKey(stock));
 
   final Stock stock;
   final StockRowActionCallback onPressed;

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

@@ -86,8 +86,8 @@ final RRect _kTickFundamentalRRect = new RRect.fromLTRBXY(-10.0, 1.0, -5.0, -1.0
 
 class _CupertinoActivityIndicatorPainter extends CustomPainter {
   _CupertinoActivityIndicatorPainter({
-    Animation<double> position,
-  }) : position = position, super(repaint: position);
+    this.position,
+  }) : super(repaint: position);
 
   final Animation<double> position;
 

packages/flutter/lib/src/gestures/multitap.dart

@@ -227,11 +227,10 @@ class DoubleTapGestureRecognizer extends GestureRecognizer {
 class _TapGesture extends _TapTracker {
 
   _TapGesture({
-    MultiTapGestureRecognizer gestureRecognizer,
+    this.gestureRecognizer,
     PointerEvent event,
     Duration longTapDelay
-  }) : gestureRecognizer = gestureRecognizer,
-       _lastPosition = event.position,
+  }) : _lastPosition = event.position,
        super(
     event: event,
     entry: GestureBinding.instance.gestureArena.add(event.pointer, gestureRecognizer)

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

@@ -164,7 +164,7 @@ class AppBar extends StatefulWidget {
     this.title,
     this.actions,
     this.flexibleSpace,
-    AppBarBottomWidget bottom,
+    this.bottom,
     this.elevation: 4,
     this.backgroundColor,
     this.brightness,
@@ -174,8 +174,7 @@ class AppBar extends StatefulWidget {
     this.centerTitle,
     this.toolbarOpacity: 1.0,
     this.bottomOpacity: 1.0,
-  }) : bottom = bottom,
-       _bottomHeight = bottom?.bottomHeight ?? 0.0,
+  }) : _bottomHeight = bottom?.bottomHeight ?? 0.0,
        super(key: key) {
     assert(elevation != null);
     assert(primary != null);
@@ -497,7 +496,7 @@ class _SliverAppBarDelegate extends SliverPersistentHeaderDelegate {
     @required this.title,
     @required this.actions,
     @required this.flexibleSpace,
-    @required AppBarBottomWidget bottom,
+    @required this.bottom,
     @required this.elevation,
     @required this.backgroundColor,
     @required this.brightness,
@@ -510,8 +509,7 @@ class _SliverAppBarDelegate extends SliverPersistentHeaderDelegate {
     @required this.topPadding,
     @required this.floating,
     @required this.pinned,
-  }) : bottom = bottom,
-      _bottomHeight = bottom?.bottomHeight ?? 0.0 {
+  }) : _bottomHeight = bottom?.bottomHeight ?? 0.0 {
     assert(primary || topPadding == 0.0);
   }
 

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

@@ -253,13 +253,12 @@ class DataTable extends StatelessWidget {
   /// otherwise it should be false.
   DataTable({
     Key key,
-    List<DataColumn> columns,
+    this.columns,
     this.sortColumnIndex,
     this.sortAscending: true,
     this.onSelectAll,
     this.rows
-  }) : columns = columns,
-       _onlyTextColumn = _initOnlyTextColumn(columns), super(key: key) {
+  }) : _onlyTextColumn = _initOnlyTextColumn(columns), super(key: key) {
     assert(columns != null);
     assert(columns.isNotEmpty);
     assert(sortColumnIndex == null || (sortColumnIndex >= 0 && sortColumnIndex < columns.length));

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

@@ -26,14 +26,11 @@ const EdgeInsets _kMenuHorizontalPadding = const EdgeInsets.symmetric(horizontal
 
 class _DropdownMenuPainter extends CustomPainter {
   _DropdownMenuPainter({
-    Color color,
-    int elevation,
+    this.color,
+    this.elevation,
     this.selectedIndex,
-    Animation<double> resize,
-  }) : color = color,
-       elevation = elevation,
-       resize = resize,
-       _painter = new BoxDecoration(
+    this.resize,
+  }) : _painter = new BoxDecoration(
          // If you add a background image here, you must provide a real
          // configuration in the paint() function and you must provide some sort
          // of onChanged callback here.
@@ -95,8 +92,8 @@ class _DropdownScrollBehavior extends ScrollBehavior {
 class _DropdownMenu<T> extends StatefulWidget {
   _DropdownMenu({
     Key key,
-    _DropdownRoute<T> route,
-  }) : route = route, super(key: key);
+    this.route,
+  }) : super(key: key);
 
   final _DropdownRoute<T> route;
 

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

@@ -206,18 +206,13 @@ class _CircularProgressIndicatorPainter extends CustomPainter {
 
   _CircularProgressIndicatorPainter({
     this.valueColor,
-    double value,
-    double headValue,
-    double tailValue,
-    int stepValue,
-    double rotationValue,
+    this.value,
+    this.headValue,
+    this.tailValue,
+    this.stepValue,
+    this.rotationValue,
     this.strokeWidth
-  }) : this.value = value,
-       this.headValue = headValue,
-       this.tailValue = tailValue,
-       this.stepValue = stepValue,
-       this.rotationValue = rotationValue,
-       arcStart = value != null
+  }) : arcStart = value != null
          ? _kStartAngle
          : _kStartAngle + tailValue * 3 / 2 * math.PI + rotationValue * math.PI * 1.7 - stepValue * 0.8 * math.PI,
        arcSweep = value != null

packages/flutter/lib/src/painting/flutter_logo.dart

@@ -50,10 +50,9 @@ class FlutterLogoDecoration extends Decoration {
   const FlutterLogoDecoration({
     this.swatch: _kDefaultSwatch,
     this.textColor: const Color(0xFF616161),
-    FlutterLogoStyle style: FlutterLogoStyle.markOnly,
+    this.style: FlutterLogoStyle.markOnly,
     this.margin: EdgeInsets.zero,
-  }) : style = style,
-       _position = style == FlutterLogoStyle.markOnly ? 0.0 : style == FlutterLogoStyle.horizontal ? 1.0 : -1.0, // ignore: CONST_EVAL_TYPE_BOOL_NUM_STRING
+  }) : _position = style == FlutterLogoStyle.markOnly ? 0.0 : style == FlutterLogoStyle.horizontal ? 1.0 : -1.0, // ignore: CONST_EVAL_TYPE_BOOL_NUM_STRING
        // (see https://github.com/dart-lang/sdk/issues/26980 for details about that ignore statement)
        _opacity = 1.0;
 

packages/flutter/lib/src/painting/text_editing.dart

@@ -94,13 +94,11 @@ class TextSelection extends TextRange {
   ///
   /// The [baseOffset] and [extentOffset] arguments must not be null.
   const TextSelection({
-    @required int baseOffset,
-    @required int extentOffset,
+    @required this.baseOffset,
+    @required this.extentOffset,
     this.affinity: TextAffinity.downstream,
     this.isDirectional: false
-  }) : baseOffset = baseOffset,
-       extentOffset = extentOffset,
-       super(
+  }) : super(
          start: baseOffset < extentOffset ? baseOffset : extentOffset,
          end: baseOffset < extentOffset ? extentOffset : baseOffset
        );

packages/flutter/lib/src/physics/spring_simulation.dart

@@ -29,12 +29,10 @@ class SpringDescription {
   /// See [mass] and [springConstant] for the units for those arguments. The
   /// damping ratio is unitless.
   SpringDescription.withDampingRatio({
-    double mass,
-    double springConstant,
+    this.mass,
+    this.springConstant,
     double ratio: 1.0
-  }) : mass = mass,
-       springConstant = springConstant,
-       damping = ratio * 2.0 * math.sqrt(mass * springConstant);
+  }) : damping = ratio * 2.0 * math.sqrt(mass * springConstant);
 
   /// The mass of the spring (m). The units are arbitrary, but all springs
   /// within a system should use the same mass units.

packages/flutter/lib/src/widgets/basic.dart

@@ -826,9 +826,9 @@ class LayoutId extends ParentDataWidget<CustomMultiChildLayout> {
   /// Both the child and the id arguments must not be null.
   LayoutId({
     Key key,
-    @required Object id,
+    @required this.id,
     @required Widget child
-  }) : id = id, super(key: key ?? new ValueKey<Object>(id), child: child) {
+  }) : super(key: key ?? new ValueKey<Object>(id), child: child) {
     assert(child != null);
     assert(id != null);
   }
@@ -2610,9 +2610,9 @@ class WidgetToRenderBoxAdapter extends LeafRenderObjectWidget {
   ///
   /// The [renderBox] argument must not be null.
   WidgetToRenderBoxAdapter({
-    @required RenderBox renderBox,
+    @required this.renderBox,
     this.onBuild
-  }) : renderBox = renderBox,
+  }) :
        // WidgetToRenderBoxAdapter objects are keyed to their render box. This
        // prevents the widget being used in the widget hierarchy in two different
        // places, which would cause the RenderBox to get inserted in multiple

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

@@ -445,9 +445,9 @@ class RenderObjectToWidgetAdapter<T extends RenderObject> extends RenderObjectWi
   /// Used by [WidgetsBinding] to attach the root widget to the [RenderView].
   RenderObjectToWidgetAdapter({
     this.child,
-    RenderObjectWithChildMixin<T> container,
+    this.container,
     this.debugShortDescription
-  }) : container = container, super(key: new GlobalObjectKey(container));
+  }) : super(key: new GlobalObjectKey(container));
 
   /// The widget below this widget in the tree.
   final Widget child;

packages/flutter/lib/src/widgets/dismissable.dart

@@ -129,8 +129,8 @@ class Dismissable extends StatefulWidget {
 class _DismissableClipper extends CustomClipper<Rect> {
   _DismissableClipper({
     this.axis,
-    Animation<FractionalOffset> moveAnimation
-  }) : moveAnimation = moveAnimation, super(reclip: moveAnimation) {
+    this.moveAnimation
+  }) : super(reclip: moveAnimation) {
     assert(axis != null);
     assert(moveAnimation != null);
   }

packages/flutter/lib/src/widgets/overlay.dart

@@ -154,7 +154,7 @@ class OverlayEntry {
 }
 
 class _OverlayEntry extends StatefulWidget {
-  _OverlayEntry(OverlayEntry entry) : entry = entry, super(key: entry._key) {
+  _OverlayEntry(this.entry) : super(key: entry._key) {
     assert(entry != null);
   }
 

packages/flutter/lib/src/widgets/table.dart

@@ -93,14 +93,13 @@ class Table extends RenderObjectWidget {
   /// arguments must not be null.
   Table({
     Key key,
-    List<TableRow> children: const <TableRow>[],
+    this.children: const <TableRow>[],
     this.columnWidths,
     this.defaultColumnWidth: const FlexColumnWidth(1.0),
     this.border,
     this.defaultVerticalAlignment: TableCellVerticalAlignment.top,
     this.textBaseline
-  }) : children = children,
-       _rowDecorations = children.any((TableRow row) => row.decoration != null)
+  }) : _rowDecorations = children.any((TableRow row) => row.decoration != null)
                          ? children.map<Decoration>((TableRow row) => row.decoration).toList(growable: false)
                          : null,
        super(key: key) {

packages/flutter/test/widgets/custom_single_child_layout_test.dart

@@ -67,7 +67,7 @@ class FixedSizeLayoutDelegate extends SingleChildLayoutDelegate {
 }
 
 class NotifierLayoutDelegate extends SingleChildLayoutDelegate {
-  NotifierLayoutDelegate(ValueNotifier<Size> size) : size = size, super(relayout: size);
+  NotifierLayoutDelegate(this.size) : super(relayout: size);
 
   final ValueNotifier<Size> size;
 

packages/flutter/test/widgets/flow_test.dart

@@ -6,9 +6,7 @@ import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 
 class TestFlowDelegate extends FlowDelegate {
-  TestFlowDelegate({
-    Animation<double> startOffset
-  }) : startOffset = startOffset, super(repaint: startOffset);
+  TestFlowDelegate({this.startOffset}) : super(repaint: startOffset);
 
   final Animation<double> startOffset;
 

packages/flutter_driver/lib/src/find.dart

@@ -161,9 +161,8 @@ class ByValueKey extends SerializableFinder {
   final String finderType = 'ByValueKey';
 
   /// Creates a finder given the key value.
-  ByValueKey(dynamic keyValue)
-    : this.keyValue = keyValue,
-      this.keyValueString = '$keyValue',
+  ByValueKey(this.keyValue)
+    : this.keyValueString = '$keyValue',
       this.keyValueType = '${keyValue.runtimeType}' {
     if (!_supportedKeyValueTypes.contains(keyValue.runtimeType))
       throw _createInvalidKeyValueTypeError('$keyValue.runtimeType');

packages/flutter_driver/lib/src/matcher_util.dart

@@ -22,9 +22,8 @@ class MatchResult {
     : hasMatched = true,
       mismatchDescription = null;
 
-  MatchResult._mismatched(String mismatchDescription)
-    : hasMatched = false,
-      mismatchDescription = mismatchDescription;
+  MatchResult._mismatched(this.mismatchDescription)
+    : hasMatched = false;
 
   /// Whether the match succeeded.
   final bool hasMatched;

packages/flutter_driver/lib/src/timeline_summary.dart

@@ -184,8 +184,6 @@ class TimedEvent {
   final Duration duration;
 
   /// Creates a timed event given begin and end timestamps in microseconds.
-  TimedEvent(int beginTimeMicros, int endTimeMicros)
-    : this.beginTimeMicros = beginTimeMicros,
-      this.endTimeMicros = endTimeMicros,
-      this.duration = new Duration(microseconds: endTimeMicros - beginTimeMicros);
+  TimedEvent(this.beginTimeMicros, this.endTimeMicros)
+    : this.duration = new Duration(microseconds: endTimeMicros - beginTimeMicros);
 }

packages/flutter_test/lib/src/all_elements.dart

@@ -23,9 +23,8 @@ Iterable<Element> collectAllElementsFrom(Element rootElement, {
 }
 
 class _DepthFirstChildIterator implements Iterator<Element> {
-  _DepthFirstChildIterator(Element rootElement, bool skipOffstage)
-    : skipOffstage = skipOffstage,
-      _stack = _reverseChildrenOf(rootElement, skipOffstage).toList();
+  _DepthFirstChildIterator(Element rootElement, this.skipOffstage)
+    : _stack = _reverseChildrenOf(rootElement, skipOffstage).toList();
 
   final bool skipOffstage;
 

packages/flutter_test/lib/src/binding.dart

@@ -829,10 +829,9 @@ const int _kPointerDecay = -2;
 
 class _LiveTestPointerRecord {
   _LiveTestPointerRecord(
-    int pointer,
+    this.pointer,
     this.position
-  ) : pointer = pointer,
-      color = new HSVColor.fromAHSV(0.8, (35.0 * pointer) % 360.0, 1.0, 1.0).toColor(),
+  ) : color = new HSVColor.fromAHSV(0.8, (35.0 * pointer) % 360.0, 1.0, 1.0).toColor(),
       decay = 1;
   final int pointer;
   final Color color;

packages/flutter_tools/lib/src/devfs.dart

@@ -298,13 +298,12 @@ class _DevFSHttpWriter {
 class DevFS {
   /// Create a [DevFS] named [fsName] for the local files in [directory].
   DevFS(VMService serviceProtocol,
-        String fsName,
+        this.fsName,
         this.rootDirectory, {
         String packagesFilePath
       })
     : _operations = new ServiceProtocolDevFSOperations(serviceProtocol),
-      _httpWriter = new _DevFSHttpWriter(fsName, serviceProtocol),
-      fsName = fsName {
+      _httpWriter = new _DevFSHttpWriter(fsName, serviceProtocol) {
     _packagesFilePath =
         packagesFilePath ?? fs.path.join(rootDirectory.path, kPackagesFileName);
   }