apply prefer_asserts_in_initializer_list lint (#10463)

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

@@ -63,12 +63,11 @@ class MaterialApp extends StatefulWidget {
     this.checkerboardOffscreenLayers: false,
     this.showSemanticsDebugger: false,
     this.debugShowCheckedModeBanner: true
-  }) : super(key: key) {
-    assert(debugShowMaterialGrid != null);
-    assert(routes != null);
-    assert(!routes.containsKey(Navigator.defaultRouteName) || (home == null));
-    assert(routes.containsKey(Navigator.defaultRouteName) || (home != null) || (onGenerateRoute != null));
- }
+  }) : assert(debugShowMaterialGrid != null),
+       assert(routes != null),
+       assert(!routes.containsKey(Navigator.defaultRouteName) || (home == null)),
+       assert(routes.containsKey(Navigator.defaultRouteName) || (home != null) || (onGenerateRoute != null)),
+       super(key: key);
 
   /// A one-line description of this app for use in the window manager.
   final String title;

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

@@ -138,13 +138,12 @@ class AppBar extends StatefulWidget implements PreferredSizeWidget {
     this.centerTitle,
     this.toolbarOpacity: 1.0,
     this.bottomOpacity: 1.0,
-  }) : preferredSize = new Size.fromHeight(kToolbarHeight + (bottom?.preferredSize?.height ?? 0.0)),
-       super(key: key) {
-    assert(elevation != null);
-    assert(primary != null);
-    assert(toolbarOpacity != null);
-    assert(bottomOpacity != null);
-  }
+  }) : assert(elevation != null),
+       assert(primary != null),
+       assert(toolbarOpacity != null),
+       assert(bottomOpacity != null),
+       preferredSize = new Size.fromHeight(kToolbarHeight + (bottom?.preferredSize?.height ?? 0.0)),
+       super(key: key);
 
   /// A widget to display before the [title].
   ///
@@ -513,9 +512,8 @@ class _SliverAppBarDelegate extends SliverPersistentHeaderDelegate {
     @required this.floating,
     @required this.pinned,
     @required this.snapConfiguration,
-  }) : _bottomHeight = bottom?.preferredSize?.height ?? 0.0 {
-    assert(primary || topPadding == 0.0);
-  }
+  }) : assert(primary || topPadding == 0.0),
+       _bottomHeight = bottom?.preferredSize?.height ?? 0.0;
 
   final Widget leading;
   final Widget title;

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

@@ -69,14 +69,13 @@ class BottomNavigationBar extends StatefulWidget {
     this.type: BottomNavigationBarType.fixed,
     this.fixedColor,
     this.iconSize: 24.0,
-  }) : super(key: key) {
-    assert(items != null);
-    assert(items.length >= 2);
-    assert(0 <= currentIndex && currentIndex < items.length);
-    assert(type != null);
-    assert(type == BottomNavigationBarType.fixed || fixedColor == null);
-    assert(iconSize != null);
-  }
+  }) : assert(items != null),
+       assert(items.length >= 2),
+       assert(0 <= currentIndex && currentIndex < items.length),
+       assert(type != null),
+       assert(type == BottomNavigationBarType.fixed || fixedColor == null),
+       assert(iconSize != null),
+       super(key: key);
 
   /// The interactive items laid out within the bottom navigation bar.
   final List<BottomNavigationBarItem> items;
@@ -450,11 +449,9 @@ class _Circle {
     @required this.index,
     @required this.color,
     @required TickerProvider vsync,
-  }) {
-    assert(state != null);
-    assert(index != null);
-    assert(color != null);
-
+  }) : assert(state != null),
+       assert(index != null),
+       assert(color != null) {
     controller = new AnimationController(
       duration: kThemeAnimationDuration,
       vsync: vsync,

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

@@ -259,14 +259,14 @@ class DataTable extends StatelessWidget {
     this.sortAscending: true,
     this.onSelectAll,
     @required this.rows
-  }) : _onlyTextColumn = _initOnlyTextColumn(columns), super(key: key) {
-    assert(columns != null);
-    assert(columns.isNotEmpty);
-    assert(sortColumnIndex == null || (sortColumnIndex >= 0 && sortColumnIndex < columns.length));
-    assert(sortAscending != null);
-    assert(rows != null);
-    assert(!rows.any((DataRow row) => row.cells.length != columns.length));
-  }
+  }) : assert(columns != null),
+       assert(columns.isNotEmpty),
+       assert(sortColumnIndex == null || (sortColumnIndex >= 0 && sortColumnIndex < columns.length)),
+       assert(sortAscending != null),
+       assert(rows != null),
+       assert(!rows.any((DataRow row) => row.cells.length != columns.length)),
+       _onlyTextColumn = _initOnlyTextColumn(columns),
+       super(key: key);
 
   /// The configuration and labels for the columns in the table.
   final List<DataColumn> columns;

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

@@ -181,14 +181,13 @@ class DayPicker extends StatelessWidget {
     @required this.lastDate,
     @required this.displayedMonth,
     this.selectableDayPredicate,
-  }) : super(key: key) {
-    assert(selectedDate != null);
-    assert(currentDate != null);
-    assert(onChanged != null);
-    assert(displayedMonth != null);
-    assert(!firstDate.isAfter(lastDate));
-    assert(selectedDate.isAfter(firstDate) || selectedDate.isAtSameMomentAs(firstDate));
-  }
+  }) : assert(selectedDate != null),
+       assert(currentDate != null),
+       assert(onChanged != null),
+       assert(displayedMonth != null),
+       assert(!firstDate.isAfter(lastDate)),
+       assert(selectedDate.isAfter(firstDate) || selectedDate.isAtSameMomentAs(firstDate)),
+       super(key: key);
 
   /// The currently selected date.
   ///
@@ -331,12 +330,11 @@ class MonthPicker extends StatefulWidget {
     @required this.firstDate,
     @required this.lastDate,
     this.selectableDayPredicate,
-  }) : super(key: key) {
-    assert(selectedDate != null);
-    assert(onChanged != null);
-    assert(!firstDate.isAfter(lastDate));
-    assert(selectedDate.isAfter(firstDate) || selectedDate.isAtSameMomentAs(firstDate));
-  }
+  }) : assert(selectedDate != null),
+       assert(onChanged != null),
+       assert(!firstDate.isAfter(lastDate)),
+       assert(selectedDate.isAfter(firstDate) || selectedDate.isAtSameMomentAs(firstDate)),
+       super(key: key);
 
   /// The currently selected date.
   ///
@@ -519,11 +517,10 @@ class YearPicker extends StatefulWidget {
     @required this.onChanged,
     @required this.firstDate,
     @required this.lastDate,
-  }) : super(key: key) {
-    assert(selectedDate != null);
-    assert(onChanged != null);
-    assert(!firstDate.isAfter(lastDate));
-  }
+  }) : assert(selectedDate != null),
+       assert(onChanged != null),
+       assert(!firstDate.isAfter(lastDate)),
+       super(key: key);
 
   /// The currently selected date.
   ///

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

@@ -319,9 +319,8 @@ class _DialogRoute<T> extends PopupRoute<T> {
     @required this.theme,
     bool barrierDismissible: true,
     @required this.child,
-  }) : _barrierDismissible = barrierDismissible {
-    assert(barrierDismissible != null);
-  }
+  }) : assert(barrierDismissible != null),
+       _barrierDismissible = barrierDismissible;
 
   final Widget child;
   final ThemeData theme;

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

@@ -266,9 +266,7 @@ class _DropdownRoute<T> extends PopupRoute<_DropdownRouteResult<T>> {
     this.elevation: 8,
     this.theme,
     @required this.style,
-  }) {
-    assert(style != null);
-  }
+  }) : assert(style != null);
 
   final List<DropdownMenuItem<T>> items;
   final Rect buttonRect;
@@ -425,11 +423,9 @@ class DropdownButton<T> extends StatefulWidget {
     this.style,
     this.iconSize: 24.0,
     this.isDense: false,
-  }) : super(key: key) {
-    assert(items != null);
-    assert(value == null ||
-      items.where((DropdownMenuItem<T> item) => item.value == value).length == 1);
-  }
+  }) : assert(items != null),
+       assert(value == null || items.where((DropdownMenuItem<T> item) => item.value == value).length == 1),
+      super(key: key);
 
   /// The list of possible items to select among.
   final List<DropdownMenuItem<T>> items;

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

@@ -43,11 +43,9 @@ class ExpansionPanel {
     @required this.headerBuilder,
     @required this.body,
     this.isExpanded: false
-  }) {
-    assert(headerBuilder != null);
-    assert(body != null);
+  }) : assert(headerBuilder != null),
+       assert(body != null),
        assert(isExpanded != null);
-  }
 
   /// The widget builder that builds the expansion panels' header.
   final ExpansionPanelHeaderBuilder headerBuilder;

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

@@ -43,13 +43,13 @@ class InkHighlight extends InkFeature {
     BorderRadius borderRadius,
     RectCallback rectCallback,
     VoidCallback onRemoved,
-  }) : _color = color,
+  }) : assert(color != null),
+       assert(shape != null),
+       _color = color,
        _shape = shape,
        _borderRadius = borderRadius ?? BorderRadius.zero,
        _rectCallback = rectCallback,
        super(controller: controller, referenceBox: referenceBox, onRemoved: onRemoved) {
-    assert(color != null);
-    assert(shape != null);
     _alphaController = new AnimationController(duration: _kHighlightFadeDuration, vsync: controller.vsync)
       ..addListener(controller.markNeedsPaint)
       ..addStatusListener(_handleAlphaStatusChanged)

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

@@ -366,10 +366,9 @@ abstract class InkFeature {
     @required MaterialInkController controller,
     @required this.referenceBox,
     this.onRemoved
-  }) : _controller = controller {
-    assert(_controller != null);
-    assert(referenceBox != null);
-  }
+  }) : assert(controller != null),
+       assert(referenceBox != null),
+       _controller = controller;
 
   /// The [MaterialInkController] associated with this [InkFeature].
   ///

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

@@ -61,10 +61,9 @@ class MaterialPageRoute<T> extends PageRoute<T> {
     RouteSettings settings: const RouteSettings(),
     this.maintainState: true,
     this.fullscreenDialog: false,
-  }) : super(settings: settings) {
-    assert(builder != null);
-    assert(opaque);
-  }
+  }) : assert(builder != null),
+       assert(opaque),
+       super(settings: settings);
 
   /// Builds the primary contents of the route.
   final WidgetBuilder builder;

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

@@ -73,21 +73,20 @@ class PaginatedDataTable extends StatefulWidget {
     this.availableRowsPerPage: const <int>[defaultRowsPerPage, defaultRowsPerPage * 2, defaultRowsPerPage * 5, defaultRowsPerPage * 10],
     this.onRowsPerPageChanged,
     @required this.source
-  }) : super(key: key) {
-    assert(header != null);
-    assert(columns != null);
-    assert(columns.isNotEmpty);
-    assert(sortColumnIndex == null || (sortColumnIndex >= 0 && sortColumnIndex < columns.length));
-    assert(sortAscending != null);
-    assert(rowsPerPage != null);
-    assert(rowsPerPage > 0);
+  }) : assert(header != null),
+       assert(columns != null),
+       assert(columns.isNotEmpty),
+       assert(sortColumnIndex == null || (sortColumnIndex >= 0 && sortColumnIndex < columns.length)),
+       assert(sortAscending != null),
+       assert(rowsPerPage != null),
+       assert(rowsPerPage > 0),
        assert(() {
          if (onRowsPerPageChanged != null)
            assert(availableRowsPerPage != null && availableRowsPerPage.contains(rowsPerPage));
          return true;
-    });
-    assert(source != null);
-  }
+       }),
+       assert(source != null),
+       super(key: key);
 
   /// The table card's header.
   ///

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

@@ -84,8 +84,8 @@ class _ScrollbarState extends State<Scrollbar> with TickerProviderStateMixin {
 }
 
 class _ScrollbarPainter extends ChangeNotifier implements CustomPainter {
-  _ScrollbarPainter(TickerProvider vsync) {
-    assert(vsync != null);
+  _ScrollbarPainter(TickerProvider vsync)
+    : assert(vsync != null) {
     _fadeController = new AnimationController(duration: _kThumbFadeDuration, vsync: vsync);
     _opacity = new CurvedAnimation(parent: _fadeController, curve: Curves.fastOutSlowIn)
       ..addListener(notifyListeners);

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

@@ -280,12 +280,12 @@ class _RenderSlider extends RenderBox implements SemanticsActionHandler {
     TextTheme textTheme,
     this.onChanged,
     TickerProvider vsync,
-  }) : _value = value,
+  }) : assert(value != null && value >= 0.0 && value <= 1.0),
+       _value = value,
        _divisions = divisions,
        _activeColor = activeColor,
        _thumbOpenAtMin = thumbOpenAtMin,
        _textTheme = textTheme {
-    assert(value != null && value >= 0.0 && value <= 1.0);
     this.label = label;
     final GestureArenaTeam team = new GestureArenaTeam();
     _drag = new HorizontalDragGestureRecognizer()

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

@@ -140,12 +140,11 @@ class Stepper extends StatefulWidget {
     this.onStepTapped,
     this.onStepContinue,
     this.onStepCancel,
-  }) : super(key: key) {
-    assert(steps != null);
-    assert(type != null);
-    assert(currentStep != null);
-    assert(0 <= currentStep && currentStep < steps.length);
-  }
+  }) : assert(steps != null),
+       assert(type != null),
+       assert(currentStep != null),
+       assert(0 <= currentStep && currentStep < steps.length),
+       super(key: key);
 
   /// The steps of the stepper whose titles, subtitles, icons always get shown.
   ///

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

@@ -63,16 +63,15 @@ import 'constants.dart';
 class TabController extends ChangeNotifier {
   /// Creates an object that manages the state required by [TabBar] and a [TabBarView].
   TabController({ int initialIndex: 0, @required this.length, @required TickerProvider vsync })
-    : _index = initialIndex,
+    : assert(length != null && length > 1),
+      assert(initialIndex != null && initialIndex >= 0 && initialIndex < length),
+      _index = initialIndex,
       _previousIndex = initialIndex,
       _animationController = new AnimationController(
         value: initialIndex.toDouble(),
         upperBound: (length - 1).toDouble(),
         vsync: vsync
-   ) {
-    assert(length != null && length > 1);
-    assert(initialIndex != null && initialIndex >= 0 && initialIndex < length);
-  }
+      );
 
   /// An animation whose value represents the current position of the [TabBar]'s
   /// selected tab indicator as well as the scrollOffsets of the [TabBar]

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

@@ -155,16 +155,15 @@ class _TabLabelBarRenderer extends RenderFlex {
     CrossAxisAlignment crossAxisAlignment,
     TextBaseline textBaseline,
     @required this.onPerformLayout,
-  }) : super(
+  }) : assert(onPerformLayout != null),
+       super(
          children: children,
          direction: direction,
          mainAxisSize: mainAxisSize,
          mainAxisAlignment: mainAxisAlignment,
          crossAxisAlignment: crossAxisAlignment,
          textBaseline: textBaseline,
-  ) {
-    assert(onPerformLayout != null);
-  }
+       );
 
   ValueChanged<List<double>> onPerformLayout;
 
@@ -411,10 +410,9 @@ class TabBar extends StatefulWidget implements PreferredSizeWidget {
     this.labelStyle,
     this.unselectedLabelColor,
     this.unselectedLabelStyle,
-  }) : super(key: key) {
-    assert(tabs != null && tabs.length > 1);
-    assert(isScrollable != null);
-  }
+  }) : assert(tabs != null && tabs.length > 1),
+       assert(isScrollable != null),
+       super(key: key);
 
   /// Typically a list of [Tab] widgets.
   final List<Widget> tabs;
@@ -741,9 +739,8 @@ class TabBarView extends StatefulWidget {
     Key key,
     @required this.children,
     this.controller,
-  }) : super(key: key) {
-    assert(children != null && children.length > 1);
-  }
+  }) : assert(children != null && children.length > 1),
+       super(key: key);
 
   /// This widget's selection and animation state.
   ///

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

@@ -30,16 +30,16 @@ abstract class RenderToggleable extends RenderConstrainedBox implements Semantic
     @required Color inactiveColor,
     ValueChanged<bool> onChanged,
     @required TickerProvider vsync,
-  }) : _value = value,
+  }) : assert(value != null),
+       assert(activeColor != null),
+       assert(inactiveColor != null),
+       assert(vsync != null),
+       _value = value,
        _activeColor = activeColor,
        _inactiveColor = inactiveColor,
        _onChanged = onChanged,
        _vsync = vsync,
        super(additionalConstraints: new BoxConstraints.tight(size)) {
-    assert(value != null);
-    assert(activeColor != null);
-    assert(inactiveColor != null);
-    assert(vsync != null);
     _tap = new TapGestureRecognizer()
       ..onTapDown = _handleTapDown
       ..onTap = _handleTap