diff --git a/packages/flutter/lib/src/rendering/binding.dart b/packages/flutter/lib/src/rendering/binding.dart
index 0bd1aae03e..04c64faec4 100644
--- a/packages/flutter/lib/src/rendering/binding.dart
+++ b/packages/flutter/lib/src/rendering/binding.dart
@@ -158,7 +158,7 @@ mixin RendererBinding on BindingBase, ServicesBinding, SchedulerBinding, Gesture
   PipelineOwner _pipelineOwner;
 
   /// The render tree that's attached to the output surface.
-  RenderView get renderView => _pipelineOwner.rootNode;
+  RenderView get renderView => _pipelineOwner.rootNode as RenderView;
   /// Sets the given [RenderView] object (which must not be null), and its tree, to
   /// be the new render tree to display. The previous tree, if any, is detached.
   set renderView(RenderView value) {
diff --git a/packages/flutter/lib/src/rendering/box.dart b/packages/flutter/lib/src/rendering/box.dart
index 8b4e814d86..d7e8e6da04 100644
--- a/packages/flutter/lib/src/rendering/box.dart
+++ b/packages/flutter/lib/src/rendering/box.dart
@@ -210,10 +210,10 @@ class BoxConstraints extends Constraints {
   /// as close as possible to the original constraints.
   BoxConstraints enforce(BoxConstraints constraints) {
     return BoxConstraints(
-      minWidth: minWidth.clamp(constraints.minWidth, constraints.maxWidth),
-      maxWidth: maxWidth.clamp(constraints.minWidth, constraints.maxWidth),
-      minHeight: minHeight.clamp(constraints.minHeight, constraints.maxHeight),
-      maxHeight: maxHeight.clamp(constraints.minHeight, constraints.maxHeight),
+      minWidth: minWidth.clamp(constraints.minWidth, constraints.maxWidth) as double,
+      maxWidth: maxWidth.clamp(constraints.minWidth, constraints.maxWidth) as double,
+      minHeight: minHeight.clamp(constraints.minHeight, constraints.maxHeight) as double,
+      maxHeight: maxHeight.clamp(constraints.minHeight, constraints.maxHeight) as double,
     );
   }
 
@@ -221,10 +221,12 @@ class BoxConstraints extends Constraints {
   /// the given width and height as possible while still respecting the original
   /// box constraints.
   BoxConstraints tighten({ double width, double height }) {
-    return BoxConstraints(minWidth: width == null ? minWidth : width.clamp(minWidth, maxWidth),
-                              maxWidth: width == null ? maxWidth : width.clamp(minWidth, maxWidth),
-                              minHeight: height == null ? minHeight : height.clamp(minHeight, maxHeight),
-                              maxHeight: height == null ? maxHeight : height.clamp(minHeight, maxHeight));
+    return BoxConstraints(
+      minWidth: width == null ? minWidth : width.clamp(minWidth, maxWidth) as double,
+      maxWidth: width == null ? maxWidth : width.clamp(minWidth, maxWidth) as double,
+      minHeight: height == null ? minHeight : height.clamp(minHeight, maxHeight) as double,
+      maxHeight: height == null ? maxHeight : height.clamp(minHeight, maxHeight) as double,
+    );
   }
 
   /// A box constraints with the width and height constraints flipped.
@@ -249,14 +251,14 @@ class BoxConstraints extends Constraints {
   /// possible to the given width.
   double constrainWidth([ double width = double.infinity ]) {
     assert(debugAssertIsValid());
-    return width.clamp(minWidth, maxWidth);
+    return width.clamp(minWidth, maxWidth) as double;
   }
 
   /// Returns the height that both satisfies the constraints and is as close as
   /// possible to the given height.
   double constrainHeight([ double height = double.infinity ]) {
     assert(debugAssertIsValid());
-    return height.clamp(minHeight, maxHeight);
+    return height.clamp(minHeight, maxHeight) as double;
   }
 
   Size _debugPropagateDebugSize(Size size, Size result) {
@@ -583,12 +585,12 @@ class BoxConstraints extends Constraints {
       return true;
     if (runtimeType != other.runtimeType)
       return false;
-    final BoxConstraints typedOther = other;
-    assert(typedOther.debugAssertIsValid());
-    return minWidth == typedOther.minWidth &&
-           maxWidth == typedOther.maxWidth &&
-           minHeight == typedOther.minHeight &&
-           maxHeight == typedOther.maxHeight;
+    assert(other is BoxConstraints && other.debugAssertIsValid());
+    return other is BoxConstraints
+        && other.minWidth == minWidth
+        && other.maxWidth == maxWidth
+        && other.minHeight == minHeight
+        && other.maxHeight == maxHeight;
   }
 
   @override
@@ -816,7 +818,7 @@ class BoxHitTestEntry extends HitTestEntry {
       super(target);
 
   @override
-  RenderBox get target => super.target;
+  RenderBox get target => super.target as RenderBox;
 
   /// The position of the hit test in the local coordinates of [target].
   final Offset localPosition;
@@ -852,11 +854,9 @@ class _IntrinsicDimensionsCacheEntry {
 
   @override
   bool operator ==(dynamic other) {
-    if (other is! _IntrinsicDimensionsCacheEntry)
-      return false;
-    final _IntrinsicDimensionsCacheEntry typedOther = other;
-    return dimension == typedOther.dimension &&
-           argument == typedOther.argument;
+    return other is _IntrinsicDimensionsCacheEntry
+        && other.dimension == dimension
+        && other.argument == argument;
   }
 
   @override
@@ -1686,8 +1686,8 @@ abstract class RenderBox extends RenderObject {
   Size get size {
     assert(hasSize, 'RenderBox was not laid out: ${toString()}');
     assert(() {
+      final Size _size = this._size;
       if (_size is _DebugSize) {
-        final _DebugSize _size = this._size;
         assert(_size._owner == this);
         if (RenderObject.debugActiveLayout != null) {
           // We are always allowed to access our own size (for print debugging
@@ -1850,7 +1850,7 @@ abstract class RenderBox extends RenderObject {
     assert(!_debugDoingBaseline, 'Please see the documentation for computeDistanceToActualBaseline for the required calling conventions of this method.');
     assert(!debugNeedsLayout);
     assert(() {
-      final RenderObject parent = this.parent;
+      final RenderObject parent = this.parent as RenderObject;
       if (owner.debugDoingLayout)
         return (RenderObject.debugActiveLayout == parent) && parent.debugDoingThisLayout;
       if (owner.debugDoingPaint)
@@ -1913,7 +1913,7 @@ abstract class RenderBox extends RenderObject {
 
   /// The box constraints most recently received from the parent.
   @override
-  BoxConstraints get constraints => super.constraints;
+  BoxConstraints get constraints => super.constraints as BoxConstraints;
 
   @override
   void debugAssertDoesMeetConstraints() {
@@ -1946,14 +1946,14 @@ abstract class RenderBox extends RenderObject {
         if (!constraints.hasBoundedWidth) {
           RenderBox node = this;
           while (!node.constraints.hasBoundedWidth && node.parent is RenderBox)
-            node = node.parent;
+            node = node.parent as RenderBox;
 
           information.add(node.describeForError('The nearest ancestor providing an unbounded width constraint is'));
         }
         if (!constraints.hasBoundedHeight) {
           RenderBox node = this;
           while (!node.constraints.hasBoundedHeight && node.parent is RenderBox)
-            node = node.parent;
+            node = node.parent as RenderBox;
 
           information.add(node.describeForError('The nearest ancestor providing an unbounded height constraint is'));
         }
@@ -2208,7 +2208,7 @@ abstract class RenderBox extends RenderObject {
       }
       return true;
     }());
-    final BoxParentData childParentData = child.parentData;
+    final BoxParentData childParentData = child.parentData as BoxParentData;
     final Offset offset = childParentData.offset;
     transform.translate(offset.dx, offset.dy);
   }
@@ -2434,7 +2434,7 @@ mixin RenderBoxContainerDefaultsMixin<ChildType extends RenderBox, ParentDataTyp
     assert(!debugNeedsLayout);
     ChildType child = firstChild;
     while (child != null) {
-      final ParentDataType childParentData = child.parentData;
+      final ParentDataType childParentData = child.parentData as ParentDataType;
       final double result = child.getDistanceToActualBaseline(baseline);
       if (result != null)
         return result + childParentData.offset.dy;
@@ -2452,7 +2452,7 @@ mixin RenderBoxContainerDefaultsMixin<ChildType extends RenderBox, ParentDataTyp
     double result;
     ChildType child = firstChild;
     while (child != null) {
-      final ParentDataType childParentData = child.parentData;
+      final ParentDataType childParentData = child.parentData as ParentDataType;
       double candidate = child.getDistanceToActualBaseline(baseline);
       if (candidate != null) {
         candidate += childParentData.offset.dy;
@@ -2479,7 +2479,7 @@ mixin RenderBoxContainerDefaultsMixin<ChildType extends RenderBox, ParentDataTyp
     // the x, y parameters have the top left of the node's box as the origin
     ChildType child = lastChild;
     while (child != null) {
-      final ParentDataType childParentData = child.parentData;
+      final ParentDataType childParentData = child.parentData as ParentDataType;
       final bool isHit = result.addWithPaintOffset(
         offset: childParentData.offset,
         position: position,
@@ -2504,7 +2504,7 @@ mixin RenderBoxContainerDefaultsMixin<ChildType extends RenderBox, ParentDataTyp
   void defaultPaint(PaintingContext context, Offset offset) {
     ChildType child = firstChild;
     while (child != null) {
-      final ParentDataType childParentData = child.parentData;
+      final ParentDataType childParentData = child.parentData as ParentDataType;
       context.paintChild(child, childParentData.offset + offset);
       child = childParentData.nextSibling;
     }
@@ -2519,8 +2519,8 @@ mixin RenderBoxContainerDefaultsMixin<ChildType extends RenderBox, ParentDataTyp
     final List<ChildType> result = <ChildType>[];
     RenderBox child = firstChild;
     while (child != null) {
-      final ParentDataType childParentData = child.parentData;
-      result.add(child);
+      final ParentDataType childParentData = child.parentData as ParentDataType;
+      result.add(child as ChildType);
       child = childParentData.nextSibling;
     }
     return result;
diff --git a/packages/flutter/lib/src/rendering/custom_layout.dart b/packages/flutter/lib/src/rendering/custom_layout.dart
index 270fef490a..3262ee09a1 100644
--- a/packages/flutter/lib/src/rendering/custom_layout.dart
+++ b/packages/flutter/lib/src/rendering/custom_layout.dart
@@ -186,12 +186,12 @@ abstract class MultiChildLayoutDelegate {
       }
       return true;
     }());
-    final MultiChildLayoutParentData childParentData = child.parentData;
+    final MultiChildLayoutParentData childParentData = child.parentData as MultiChildLayoutParentData;
     childParentData.offset = offset;
   }
 
   DiagnosticsNode _debugDescribeChild(RenderBox child) {
-    final MultiChildLayoutParentData childParentData = child.parentData;
+    final MultiChildLayoutParentData childParentData = child.parentData as MultiChildLayoutParentData;
     return DiagnosticsProperty<RenderBox>('${childParentData.id}', child);
   }
 
@@ -212,7 +212,7 @@ abstract class MultiChildLayoutDelegate {
       _idToChild = <Object, RenderBox>{};
       RenderBox child = firstChild;
       while (child != null) {
-        final MultiChildLayoutParentData childParentData = child.parentData;
+        final MultiChildLayoutParentData childParentData = child.parentData as MultiChildLayoutParentData;
         assert(() {
           if (childParentData.id == null) {
             throw FlutterError.fromParts(<DiagnosticsNode>[
diff --git a/packages/flutter/lib/src/rendering/debug_overflow_indicator.dart b/packages/flutter/lib/src/rendering/debug_overflow_indicator.dart
index 58ed36231d..7911b0a0a3 100644
--- a/packages/flutter/lib/src/rendering/debug_overflow_indicator.dart
+++ b/packages/flutter/lib/src/rendering/debug_overflow_indicator.dart
@@ -284,7 +284,7 @@ mixin DebugOverflowIndicatorMixin on RenderObject {
     final List<_OverflowRegionData> overflowRegions = _calculateOverflowRegions(overflow, containerRect);
     for (_OverflowRegionData region in overflowRegions) {
       context.canvas.drawRect(region.rect.shift(offset), _indicatorPaint);
-      final TextSpan textSpan = _indicatorLabel[region.side.index].text;
+      final TextSpan textSpan = _indicatorLabel[region.side.index].text as TextSpan;
       if (textSpan?.text != region.label) {
         _indicatorLabel[region.side.index].text = TextSpan(
           text: region.label,
diff --git a/packages/flutter/lib/src/rendering/editable.dart b/packages/flutter/lib/src/rendering/editable.dart
index a195a966e8..dfef98c15c 100644
--- a/packages/flutter/lib/src/rendering/editable.dart
+++ b/packages/flutter/lib/src/rendering/editable.dart
@@ -733,7 +733,7 @@ class RenderEditable extends RenderBox with RelayoutWhenSystemFontsChangeMixin {
   }
 
   /// The text to display.
-  TextSpan get text => _textPainter.text;
+  TextSpan get text => _textPainter.text as TextSpan;
   final TextPainter _textPainter;
   set text(TextSpan value) {
     if (_textPainter.text == value)
@@ -1955,8 +1955,8 @@ class RenderEditable extends RenderBox with RelayoutWhenSystemFontsChangeMixin {
   void _paintHandleLayers(PaintingContext context, List<TextSelectionPoint> endpoints) {
     Offset startPoint = endpoints[0].point;
     startPoint = Offset(
-      startPoint.dx.clamp(0.0, size.width),
-      startPoint.dy.clamp(0.0, size.height),
+      startPoint.dx.clamp(0.0, size.width) as double,
+      startPoint.dy.clamp(0.0, size.height) as double,
     );
     context.pushLayer(
       LeaderLayer(link: startHandleLayerLink, offset: startPoint),
@@ -1966,8 +1966,8 @@ class RenderEditable extends RenderBox with RelayoutWhenSystemFontsChangeMixin {
     if (endpoints.length == 2) {
       Offset endPoint = endpoints[1].point;
       endPoint = Offset(
-        endPoint.dx.clamp(0.0, size.width),
-        endPoint.dy.clamp(0.0, size.height),
+        endPoint.dx.clamp(0.0, size.width) as double,
+        endPoint.dy.clamp(0.0, size.height) as double,
       );
       context.pushLayer(
         LeaderLayer(link: endHandleLayerLink, offset: endPoint),
diff --git a/packages/flutter/lib/src/rendering/flex.dart b/packages/flutter/lib/src/rendering/flex.dart
index 9e79d3e870..59f0b6423f 100644
--- a/packages/flutter/lib/src/rendering/flex.dart
+++ b/packages/flutter/lib/src/rendering/flex.dart
@@ -502,7 +502,7 @@ class RenderFlex extends RenderBox with ContainerRenderObjectMixin<RenderBox, Fl
         } else {
           inflexibleSpace += childSize(child, extent);
         }
-        final FlexParentData childParentData = child.parentData;
+        final FlexParentData childParentData = child.parentData as FlexParentData;
         child = childParentData.nextSibling;
       }
       return maxFlexFractionSoFar * totalFlex + inflexibleSpace;
@@ -537,7 +537,7 @@ class RenderFlex extends RenderBox with ContainerRenderObjectMixin<RenderBox, Fl
           inflexibleSpace += mainSize;
           maxCrossSize = math.max(maxCrossSize, crossSize);
         }
-        final FlexParentData childParentData = child.parentData;
+        final FlexParentData childParentData = child.parentData as FlexParentData;
         child = childParentData.nextSibling;
       }
 
@@ -552,7 +552,7 @@ class RenderFlex extends RenderBox with ContainerRenderObjectMixin<RenderBox, Fl
         final int flex = _getFlex(child);
         if (flex > 0)
           maxCrossSize = math.max(maxCrossSize, childSize(child, spacePerFlex * flex));
-        final FlexParentData childParentData = child.parentData;
+        final FlexParentData childParentData = child.parentData as FlexParentData;
         child = childParentData.nextSibling;
       }
 
@@ -604,12 +604,12 @@ class RenderFlex extends RenderBox with ContainerRenderObjectMixin<RenderBox, Fl
   }
 
   int _getFlex(RenderBox child) {
-    final FlexParentData childParentData = child.parentData;
+    final FlexParentData childParentData = child.parentData as FlexParentData;
     return childParentData.flex ?? 0;
   }
 
   FlexFit _getFit(RenderBox child) {
-    final FlexParentData childParentData = child.parentData;
+    final FlexParentData childParentData = child.parentData as FlexParentData;
     return childParentData.fit ?? FlexFit.tight;
   }
 
@@ -648,7 +648,7 @@ class RenderFlex extends RenderBox with ContainerRenderObjectMixin<RenderBox, Fl
     RenderBox child = firstChild;
     RenderBox lastFlexChild;
     while (child != null) {
-      final FlexParentData childParentData = child.parentData;
+      final FlexParentData childParentData = child.parentData as FlexParentData;
       totalChildren++;
       final int flex = _getFlex(child);
       if (flex > 0) {
@@ -670,13 +670,13 @@ class RenderFlex extends RenderBox with ContainerRenderObjectMixin<RenderBox, Fl
             switch (_direction) {
               case Axis.horizontal:
                 while (!node.constraints.hasBoundedWidth && node.parent is RenderBox)
-                  node = node.parent;
+                  node = node.parent as RenderBox;
                 if (!node.constraints.hasBoundedWidth)
                   node = null;
                 break;
               case Axis.vertical:
                 while (!node.constraints.hasBoundedHeight && node.parent is RenderBox)
-                  node = node.parent;
+                  node = node.parent as RenderBox;
                 if (!node.constraints.hasBoundedHeight)
                   node = null;
                 break;
@@ -830,7 +830,7 @@ class RenderFlex extends RenderBox with ContainerRenderObjectMixin<RenderBox, Fl
             crossSize = maxSizeAboveBaseline + maxSizeBelowBaseline;
           }
         }
-        final FlexParentData childParentData = child.parentData;
+        final FlexParentData childParentData = child.parentData as FlexParentData;
         child = childParentData.nextSibling;
       }
     }
@@ -892,7 +892,7 @@ class RenderFlex extends RenderBox with ContainerRenderObjectMixin<RenderBox, Fl
     double childMainPosition = flipMainAxis ? actualSize - leadingSpace : leadingSpace;
     child = firstChild;
     while (child != null) {
-      final FlexParentData childParentData = child.parentData;
+      final FlexParentData childParentData = child.parentData as FlexParentData;
       double childCrossPosition;
       switch (_crossAxisAlignment) {
         case CrossAxisAlignment.start:
diff --git a/packages/flutter/lib/src/rendering/flow.dart b/packages/flutter/lib/src/rendering/flow.dart
index 27331c6a60..b2a7d458a5 100644
--- a/packages/flutter/lib/src/rendering/flow.dart
+++ b/packages/flutter/lib/src/rendering/flow.dart
@@ -287,7 +287,7 @@ class RenderFlow extends RenderBox
       _randomAccessChildren.add(child);
       final BoxConstraints innerConstraints = _delegate.getConstraintsForChild(i, constraints);
       child.layout(innerConstraints, parentUsesSize: true);
-      final FlowParentData childParentData = child.parentData;
+      final FlowParentData childParentData = child.parentData as FlowParentData;
       childParentData.offset = Offset.zero;
       child = childParentData.nextSibling;
       i += 1;
@@ -315,7 +315,7 @@ class RenderFlow extends RenderBox
   void paintChild(int i, { Matrix4 transform, double opacity = 1.0 }) {
     transform ??= Matrix4.identity();
     final RenderBox child = _randomAccessChildren[i];
-    final FlowParentData childParentData = child.parentData;
+    final FlowParentData childParentData = child.parentData as FlowParentData;
     assert(() {
       if (childParentData._transform != null) {
         throw FlutterError.fromParts(<DiagnosticsNode>[
@@ -353,7 +353,7 @@ class RenderFlow extends RenderBox
     _paintingContext = context;
     _paintingOffset = offset;
     for (RenderBox child in _randomAccessChildren) {
-      final FlowParentData childParentData = child.parentData;
+      final FlowParentData childParentData = child.parentData as FlowParentData;
       childParentData._transform = null;
     }
     try {
@@ -377,7 +377,7 @@ class RenderFlow extends RenderBox
       if (childIndex >= children.length)
         continue;
       final RenderBox child = children[childIndex];
-      final FlowParentData childParentData = child.parentData;
+      final FlowParentData childParentData = child.parentData as FlowParentData;
       final Matrix4 transform = childParentData._transform;
       if (transform == null)
         continue;
@@ -396,7 +396,7 @@ class RenderFlow extends RenderBox
 
   @override
   void applyPaintTransform(RenderBox child, Matrix4 transform) {
-    final FlowParentData childParentData = child.parentData;
+    final FlowParentData childParentData = child.parentData as FlowParentData;
     if (childParentData._transform != null)
       transform.multiply(childParentData._transform);
     super.applyPaintTransform(child, transform);
diff --git a/packages/flutter/lib/src/rendering/layer.dart b/packages/flutter/lib/src/rendering/layer.dart
index 6ffa9cf623..e1bf4ce947 100644
--- a/packages/flutter/lib/src/rendering/layer.dart
+++ b/packages/flutter/lib/src/rendering/layer.dart
@@ -4,8 +4,7 @@
 
 import 'dart:async';
 import 'dart:collection';
-import 'dart:ui' as ui show EngineLayer, Image, ImageFilter, PathMetric,
-                            Picture, PictureRecorder, Scene, SceneBuilder;
+import 'dart:ui' as ui;
 
 import 'package:flutter/foundation.dart';
 import 'package:flutter/gestures.dart';
@@ -103,7 +102,7 @@ abstract class Layer extends AbstractNode with DiagnosticableTreeMixin {
   /// Only subclasses of [ContainerLayer] can have children in the layer tree.
   /// All other layer classes are used for leaves in the layer tree.
   @override
-  ContainerLayer get parent => super.parent;
+  ContainerLayer get parent => super.parent as ContainerLayer;
 
   // Whether this layer has any changes since its last call to [addToScene].
   //
@@ -1158,7 +1157,11 @@ class OffsetLayer extends ContainerLayer {
     // retained rendering, we don't want to push the offset down to each leaf
     // node. Otherwise, changing an offset layer on the very high level could
     // cascade the change to too many leaves.
-    engineLayer = builder.pushOffset(layerOffset.dx + offset.dx, layerOffset.dy + offset.dy, oldLayer: _engineLayer);
+    engineLayer = builder.pushOffset(
+      layerOffset.dx + offset.dx,
+      layerOffset.dy + offset.dy,
+      oldLayer: _engineLayer as ui.OffsetEngineLayer,
+    );
     addChildrenToScene(builder);
     builder.pop();
   }
@@ -1281,7 +1284,11 @@ class ClipRectLayer extends ContainerLayer {
     }());
     if (enabled) {
       final Rect shiftedClipRect = layerOffset == Offset.zero ? clipRect : clipRect.shift(layerOffset);
-      engineLayer = builder.pushClipRect(shiftedClipRect, clipBehavior: clipBehavior, oldLayer: _engineLayer);
+      engineLayer = builder.pushClipRect(
+        shiftedClipRect,
+        clipBehavior: clipBehavior,
+        oldLayer: _engineLayer as ui.ClipRectEngineLayer,
+      );
     } else {
       engineLayer = null;
     }
@@ -1362,7 +1369,11 @@ class ClipRRectLayer extends ContainerLayer {
     }());
     if (enabled) {
       final RRect shiftedClipRRect = layerOffset == Offset.zero ? clipRRect : clipRRect.shift(layerOffset);
-      engineLayer = builder.pushClipRRect(shiftedClipRRect, clipBehavior: clipBehavior, oldLayer: _engineLayer);
+      engineLayer = builder.pushClipRRect(
+        shiftedClipRRect,
+        clipBehavior: clipBehavior,
+        oldLayer: _engineLayer as ui.ClipRRectEngineLayer,
+      );
     } else {
       engineLayer = null;
     }
@@ -1443,7 +1454,11 @@ class ClipPathLayer extends ContainerLayer {
     }());
     if (enabled) {
       final Path shiftedPath = layerOffset == Offset.zero ? clipPath : clipPath.shift(layerOffset);
-      engineLayer = builder.pushClipPath(shiftedPath, clipBehavior: clipBehavior, oldLayer: _engineLayer);
+      engineLayer = builder.pushClipPath(
+        shiftedPath,
+        clipBehavior: clipBehavior,
+        oldLayer: _engineLayer as ui.ClipPathEngineLayer,
+      );
     } else {
       engineLayer = null;
     }
@@ -1486,7 +1501,10 @@ class ColorFilterLayer extends ContainerLayer {
   @override
   void addToScene(ui.SceneBuilder builder, [ Offset layerOffset = Offset.zero ]) {
     assert(colorFilter != null);
-    engineLayer = builder.pushColorFilter(colorFilter, oldLayer: _engineLayer);
+    engineLayer = builder.pushColorFilter(
+      colorFilter,
+      oldLayer: _engineLayer as ui.ColorFilterEngineLayer,
+    );
     addChildrenToScene(builder, layerOffset);
     builder.pop();
   }
@@ -1546,7 +1564,10 @@ class TransformLayer extends OffsetLayer {
       _lastEffectiveTransform = Matrix4.translationValues(totalOffset.dx, totalOffset.dy, 0.0)
         ..multiply(_lastEffectiveTransform);
     }
-    engineLayer = builder.pushTransform(_lastEffectiveTransform.storage, oldLayer: _engineLayer);
+    engineLayer = builder.pushTransform(
+      _lastEffectiveTransform.storage,
+      oldLayer: _engineLayer as ui.TransformEngineLayer,
+    );
     addChildrenToScene(builder);
     builder.pop();
   }
@@ -1656,7 +1677,11 @@ class OpacityLayer extends ContainerLayer {
     }());
 
     if (enabled)
-      engineLayer = builder.pushOpacity(alpha, offset: offset + layerOffset, oldLayer: _engineLayer);
+      engineLayer = builder.pushOpacity(
+        alpha,
+        offset: offset + layerOffset,
+        oldLayer: _engineLayer as ui.OpacityEngineLayer,
+      );
     else
       engineLayer = null;
     addChildrenToScene(builder);
@@ -1748,7 +1773,12 @@ class ShaderMaskLayer extends ContainerLayer {
     assert(blendMode != null);
     assert(layerOffset != null);
     final Rect shiftedMaskRect = layerOffset == Offset.zero ? maskRect : maskRect.shift(layerOffset);
-    engineLayer = builder.pushShaderMask(shader, shiftedMaskRect, blendMode, oldLayer: _engineLayer);
+    engineLayer = builder.pushShaderMask(
+      shader,
+      shiftedMaskRect,
+      blendMode,
+      oldLayer: _engineLayer as ui.ShaderMaskEngineLayer,
+    );
     addChildrenToScene(builder, layerOffset);
     builder.pop();
   }
@@ -1786,7 +1816,10 @@ class BackdropFilterLayer extends ContainerLayer {
   @override
   void addToScene(ui.SceneBuilder builder, [ Offset layerOffset = Offset.zero ]) {
     assert(filter != null);
-    engineLayer = builder.pushBackdropFilter(filter, oldLayer: _engineLayer);
+    engineLayer = builder.pushBackdropFilter(
+      filter,
+      oldLayer: _engineLayer as ui.BackdropFilterEngineLayer,
+    );
     addChildrenToScene(builder, layerOffset);
     builder.pop();
   }
@@ -1923,7 +1956,7 @@ class PhysicalModelLayer extends ContainerLayer {
         color: color,
         shadowColor: shadowColor,
         clipBehavior: clipBehavior,
-        oldLayer: _engineLayer,
+        oldLayer: _engineLayer as ui.PhysicalShapeEngineLayer,
       );
     } else {
       engineLayer = null;
@@ -2036,7 +2069,10 @@ class LeaderLayer extends ContainerLayer {
     assert(offset != null);
     _lastOffset = offset + layerOffset;
     if (_lastOffset != Offset.zero)
-      engineLayer = builder.pushTransform(Matrix4.translationValues(_lastOffset.dx, _lastOffset.dy, 0.0).storage, oldLayer: _engineLayer);
+      engineLayer = builder.pushTransform(
+        Matrix4.translationValues(_lastOffset.dx, _lastOffset.dy, 0.0).storage,
+        oldLayer: _engineLayer as ui.TransformEngineLayer,
+      );
     addChildrenToScene(builder);
     if (_lastOffset != Offset.zero)
       builder.pop();
@@ -2278,14 +2314,20 @@ class FollowerLayer extends ContainerLayer {
     }
     _establishTransform();
     if (_lastTransform != null) {
-      engineLayer = builder.pushTransform(_lastTransform.storage, oldLayer: _engineLayer);
+      engineLayer = builder.pushTransform(
+        _lastTransform.storage,
+        oldLayer: _engineLayer as ui.TransformEngineLayer,
+      );
       addChildrenToScene(builder);
       builder.pop();
       _lastOffset = unlinkedOffset + layerOffset;
     } else {
       _lastOffset = null;
       final Matrix4 matrix = Matrix4.translationValues(unlinkedOffset.dx, unlinkedOffset.dy, .0);
-      engineLayer = builder.pushTransform(matrix.storage, oldLayer: _engineLayer);
+      engineLayer = builder.pushTransform(
+        matrix.storage,
+        oldLayer: _engineLayer as ui.TransformEngineLayer,
+      );
       addChildrenToScene(builder);
       builder.pop();
     }
@@ -2425,7 +2467,7 @@ class AnnotatedRegionLayer<T> extends ContainerLayer {
     if (T == S) {
       isAbsorbed = isAbsorbed || opaque;
       final Object untypedValue = value;
-      final S typedValue = untypedValue;
+      final S typedValue = untypedValue as S;
       result.add(AnnotationEntry<S>(
         annotation: typedValue,
         localPosition: localPosition,
diff --git a/packages/flutter/lib/src/rendering/list_body.dart b/packages/flutter/lib/src/rendering/list_body.dart
index f2d92750f5..cd11d67fad 100644
--- a/packages/flutter/lib/src/rendering/list_body.dart
+++ b/packages/flutter/lib/src/rendering/list_body.dart
@@ -126,7 +126,7 @@ class RenderListBody extends RenderBox
         final BoxConstraints innerConstraints = BoxConstraints.tightFor(height: constraints.maxHeight);
         while (child != null) {
           child.layout(innerConstraints, parentUsesSize: true);
-          final ListBodyParentData childParentData = child.parentData;
+          final ListBodyParentData childParentData = child.parentData as ListBodyParentData;
           childParentData.offset = Offset(mainAxisExtent, 0.0);
           mainAxisExtent += child.size.width;
           assert(child.parentData == childParentData);
@@ -138,7 +138,7 @@ class RenderListBody extends RenderBox
         final BoxConstraints innerConstraints = BoxConstraints.tightFor(height: constraints.maxHeight);
         while (child != null) {
           child.layout(innerConstraints, parentUsesSize: true);
-          final ListBodyParentData childParentData = child.parentData;
+          final ListBodyParentData childParentData = child.parentData as ListBodyParentData;
           mainAxisExtent += child.size.width;
           assert(child.parentData == childParentData);
           child = childParentData.nextSibling;
@@ -146,7 +146,7 @@ class RenderListBody extends RenderBox
         double position = 0.0;
         child = firstChild;
         while (child != null) {
-          final ListBodyParentData childParentData = child.parentData;
+          final ListBodyParentData childParentData = child.parentData as ListBodyParentData;
           position += child.size.width;
           childParentData.offset = Offset(mainAxisExtent - position, 0.0);
           assert(child.parentData == childParentData);
@@ -158,7 +158,7 @@ class RenderListBody extends RenderBox
         final BoxConstraints innerConstraints = BoxConstraints.tightFor(width: constraints.maxWidth);
         while (child != null) {
           child.layout(innerConstraints, parentUsesSize: true);
-          final ListBodyParentData childParentData = child.parentData;
+          final ListBodyParentData childParentData = child.parentData as ListBodyParentData;
           childParentData.offset = Offset(0.0, mainAxisExtent);
           mainAxisExtent += child.size.height;
           assert(child.parentData == childParentData);
@@ -170,7 +170,7 @@ class RenderListBody extends RenderBox
         final BoxConstraints innerConstraints = BoxConstraints.tightFor(width: constraints.maxWidth);
         while (child != null) {
           child.layout(innerConstraints, parentUsesSize: true);
-          final ListBodyParentData childParentData = child.parentData;
+          final ListBodyParentData childParentData = child.parentData as ListBodyParentData;
           mainAxisExtent += child.size.height;
           assert(child.parentData == childParentData);
           child = childParentData.nextSibling;
@@ -178,7 +178,7 @@ class RenderListBody extends RenderBox
         double position = 0.0;
         child = firstChild;
         while (child != null) {
-          final ListBodyParentData childParentData = child.parentData;
+          final ListBodyParentData childParentData = child.parentData as ListBodyParentData;
           position += child.size.height;
           childParentData.offset = Offset(0.0, mainAxisExtent - position);
           assert(child.parentData == childParentData);
@@ -201,7 +201,7 @@ class RenderListBody extends RenderBox
     RenderBox child = firstChild;
     while (child != null) {
       extent = math.max(extent, childSize(child));
-      final ListBodyParentData childParentData = child.parentData;
+      final ListBodyParentData childParentData = child.parentData as ListBodyParentData;
       child = childParentData.nextSibling;
     }
     return extent;
@@ -212,7 +212,7 @@ class RenderListBody extends RenderBox
     RenderBox child = firstChild;
     while (child != null) {
       extent += childSize(child);
-      final ListBodyParentData childParentData = child.parentData;
+      final ListBodyParentData childParentData = child.parentData as ListBodyParentData;
       child = childParentData.nextSibling;
     }
     return extent;
diff --git a/packages/flutter/lib/src/rendering/list_wheel_viewport.dart b/packages/flutter/lib/src/rendering/list_wheel_viewport.dart
index 6b780ae39b..ade2483e76 100644
--- a/packages/flutter/lib/src/rendering/list_wheel_viewport.dart
+++ b/packages/flutter/lib/src/rendering/list_wheel_viewport.dart
@@ -598,7 +598,7 @@ class RenderListWheelViewport
   /// Gets the index of a child by looking at its parentData.
   int indexOf(RenderBox child) {
     assert(child != null);
-    final ListWheelParentData childParentData = child.parentData;
+    final ListWheelParentData childParentData = child.parentData as ListWheelParentData;
     assert(childParentData.index != null);
     return childParentData.index;
   }
@@ -625,7 +625,7 @@ class RenderListWheelViewport
 
   void _layoutChild(RenderBox child, BoxConstraints constraints, int index) {
     child.layout(constraints, parentUsesSize: true);
-    final ListWheelParentData childParentData = child.parentData;
+    final ListWheelParentData childParentData = child.parentData as ListWheelParentData;
     // Centers the child horizontally.
     final double crossPosition = size.width / 2.0 - child.size.width / 2.0;
     childParentData.offset = Offset(crossPosition, indexToScrollOffset(index));
@@ -780,12 +780,12 @@ class RenderListWheelViewport
   /// Paints all children visible in the current viewport.
   void _paintVisibleChildren(PaintingContext context, Offset offset) {
     RenderBox childToPaint = firstChild;
-    ListWheelParentData childParentData = childToPaint?.parentData;
+    ListWheelParentData childParentData = childToPaint?.parentData as ListWheelParentData;
 
     while (childParentData != null) {
       _paintTransformedChild(childToPaint, context, offset, childParentData.offset);
       childToPaint = childAfter(childToPaint);
-      childParentData = childToPaint?.parentData;
+      childParentData = childToPaint?.parentData as ListWheelParentData;
     }
   }
 
@@ -971,7 +971,7 @@ class RenderListWheelViewport
   /// painting coordinates** system.
   @override
   void applyPaintTransform(RenderBox child, Matrix4 transform) {
-    final ListWheelParentData parentData = child?.parentData;
+    final ListWheelParentData parentData = child?.parentData as ListWheelParentData;
     transform.translate(0.0, _getUntransformedPaintingCoordinateY(parentData.offset.dy));
   }
 
@@ -997,9 +997,9 @@ class RenderListWheelViewport
     // `child` will be the last RenderObject before the viewport when walking up from `target`.
     RenderObject child = target;
     while (child.parent != this)
-      child = child.parent;
+      child = child.parent as RenderObject;
 
-    final ListWheelParentData parentData = child.parentData;
+    final ListWheelParentData parentData = child.parentData as ListWheelParentData;
     final double targetOffset = parentData.offset.dy; // the so-called "centerPosition"
 
     final Matrix4 transform = target.getTransformTo(child);
diff --git a/packages/flutter/lib/src/rendering/object.dart b/packages/flutter/lib/src/rendering/object.dart
index c5ebbd537a..1da7a3bed3 100644
--- a/packages/flutter/lib/src/rendering/object.dart
+++ b/packages/flutter/lib/src/rendering/object.dart
@@ -112,7 +112,7 @@ class PaintingContext extends ClipContext {
       );
       return true;
     }());
-    OffsetLayer childLayer = child._layer;
+    OffsetLayer childLayer = child._layer as OffsetLayer;
     if (childLayer == null) {
       assert(debugAlsoPaintedParent);
       // Not using the `layer` setter because the setter asserts that we not
@@ -211,7 +211,7 @@ class PaintingContext extends ClipContext {
       }());
     }
     assert(child._layer is OffsetLayer);
-    final OffsetLayer childOffsetLayer = child._layer;
+    final OffsetLayer childOffsetLayer = child._layer as OffsetLayer;
     childOffsetLayer.offset = offset;
     appendLayer(child._layer);
   }
@@ -1388,7 +1388,7 @@ abstract class RenderObject extends AbstractNode with DiagnosticableTreeMixin im
           result = true;
           break;
         }
-        node = node.parent;
+        node = node.parent as RenderObject;
       }
       return true;
     }());
@@ -1396,7 +1396,7 @@ abstract class RenderObject extends AbstractNode with DiagnosticableTreeMixin im
   }
 
   @override
-  PipelineOwner get owner => super.owner;
+  PipelineOwner get owner => super.owner as PipelineOwner;
 
   @override
   void attach(PipelineOwner owner) {
@@ -1478,7 +1478,7 @@ abstract class RenderObject extends AbstractNode with DiagnosticableTreeMixin im
     while (node != _relayoutBoundary) {
       assert(node._relayoutBoundary == _relayoutBoundary);
       assert(node.parent != null);
-      node = node.parent;
+      node = node.parent as RenderObject;
       if ((!node._needsLayout) && (!node._debugDoingThisLayout))
         return false;
     }
@@ -1559,7 +1559,7 @@ abstract class RenderObject extends AbstractNode with DiagnosticableTreeMixin im
   @protected
   void markParentNeedsLayout() {
     _needsLayout = true;
-    final RenderObject parent = this.parent;
+    final RenderObject parent = this.parent as RenderObject;
     if (!_doingThisLayoutWithCallback) {
       parent.markNeedsLayout();
     } else {
@@ -1697,8 +1697,7 @@ abstract class RenderObject extends AbstractNode with DiagnosticableTreeMixin im
     if (!parentUsesSize || sizedByParent || constraints.isTight || parent is! RenderObject) {
       relayoutBoundary = this;
     } else {
-      final RenderObject parent = this.parent;
-      relayoutBoundary = parent._relayoutBoundary;
+      relayoutBoundary = (parent as RenderObject)._relayoutBoundary;
     }
     assert(() {
       _debugCanParentUseSize = parentUsesSize;
@@ -1864,7 +1863,7 @@ abstract class RenderObject extends AbstractNode with DiagnosticableTreeMixin im
     assert(!_doingThisLayoutWithCallback);
     _doingThisLayoutWithCallback = true;
     try {
-      owner._enableMutationsToDirtySubtrees(() { callback(constraints); });
+      owner._enableMutationsToDirtySubtrees(() { callback(constraints as T); });
     } finally {
       _doingThisLayoutWithCallback = false;
     }
@@ -2011,7 +2010,7 @@ abstract class RenderObject extends AbstractNode with DiagnosticableTreeMixin im
       return;
     _needsCompositingBitsUpdate = true;
     if (parent is RenderObject) {
-      final RenderObject parent = this.parent;
+      final RenderObject parent = this.parent as RenderObject;
       if (parent._needsCompositingBitsUpdate)
         return;
       if (!isRepaintBoundary && !parent.isRepaintBoundary) {
@@ -2123,7 +2122,7 @@ abstract class RenderObject extends AbstractNode with DiagnosticableTreeMixin im
         owner.requestVisualUpdate();
       }
     } else if (parent is RenderObject) {
-      final RenderObject parent = this.parent;
+      final RenderObject parent = this.parent as RenderObject;
       parent.markNeedsPaint();
       assert(parent == this.parent);
     } else {
@@ -2154,7 +2153,7 @@ abstract class RenderObject extends AbstractNode with DiagnosticableTreeMixin im
     assert(!_layer.attached);
     AbstractNode ancestor = parent;
     while (ancestor is RenderObject) {
-      final RenderObject node = ancestor;
+      final RenderObject node = ancestor as RenderObject;
       if (node.isRepaintBoundary) {
         if (node._layer == null)
           break; // looks like the subtree here has never been painted. let it handle itself.
@@ -2333,7 +2332,7 @@ abstract class RenderObject extends AbstractNode with DiagnosticableTreeMixin im
         ancestor = rootNode;
     }
     final List<RenderObject> renderers = <RenderObject>[];
-    for (RenderObject renderer = this; renderer != ancestor; renderer = renderer.parent) {
+    for (RenderObject renderer = this; renderer != ancestor; renderer = renderer.parent as RenderObject) {
       assert(renderer != null); // Failed to find ancestor in parent chain.
       renderers.add(renderer);
     }
@@ -2452,7 +2451,7 @@ abstract class RenderObject extends AbstractNode with DiagnosticableTreeMixin im
     if (_semantics != null && !_semantics.isMergedIntoParent) {
       _semantics.sendEvent(semanticsEvent);
     } else if (parent != null) {
-      final RenderObject renderParent = parent;
+      final RenderObject renderParent = parent as RenderObject;
       renderParent.sendSemanticsEvent(semanticsEvent);
     }
   }
@@ -2534,7 +2533,7 @@ abstract class RenderObject extends AbstractNode with DiagnosticableTreeMixin im
         break;
       node._needsSemanticsUpdate = true;
 
-      node = node.parent;
+      node = node.parent as RenderObject;
       isEffectiveSemanticsBoundary = node._semanticsConfiguration.isSemanticBoundary;
       if (isEffectiveSemanticsBoundary && node._semantics == null) {
         // We have reached a semantics boundary that doesn't own a semantics node.
@@ -2575,7 +2574,7 @@ abstract class RenderObject extends AbstractNode with DiagnosticableTreeMixin im
       mergeIntoParent: _semantics?.parent?.isPartOfNodeMerging ?? false,
     );
     assert(fragment is _InterestingSemanticsFragment);
-    final _InterestingSemanticsFragment interestingFragment = fragment;
+    final _InterestingSemanticsFragment interestingFragment = fragment as _InterestingSemanticsFragment;
     final SemanticsNode node = interestingFragment.compileChildren(
       parentSemanticsClipRect: _semantics?.parentSemanticsClipRect,
       parentPaintClipRect: _semantics?.parentPaintClipRect,
@@ -2676,7 +2675,7 @@ abstract class RenderObject extends AbstractNode with DiagnosticableTreeMixin im
         dropsSemanticsOfPreviousSiblings: dropSemanticsOfPreviousSiblings,
       );
       if (config.isSemanticBoundary) {
-        final _SwitchableSemanticsFragment fragment = result;
+        final _SwitchableSemanticsFragment fragment = result as _SwitchableSemanticsFragment;
         fragment.markAsExplicit();
       }
     }
@@ -2717,7 +2716,8 @@ abstract class RenderObject extends AbstractNode with DiagnosticableTreeMixin im
     Iterable<SemanticsNode> children,
   ) {
     assert(node == _semantics);
-    node.updateWith(config: config, childrenInInversePaintOrder: children);
+    // TODO(a14n): remove the following cast by updating type of parameter in either updateWith or assembleSemanticsNode
+    node.updateWith(config: config, childrenInInversePaintOrder: children as List<SemanticsNode>);
   }
 
   // EVENTS
@@ -2753,9 +2753,9 @@ abstract class RenderObject extends AbstractNode with DiagnosticableTreeMixin im
     String header = describeIdentity(this);
     if (_relayoutBoundary != null && _relayoutBoundary != this) {
       int count = 1;
-      RenderObject target = parent;
+      RenderObject target = parent as RenderObject;
       while (target != null && target != _relayoutBoundary) {
-        target = target.parent;
+        target = target.parent as RenderObject;
         count += 1;
       }
       header += ' relayoutBoundary=up$count';
@@ -2869,7 +2869,7 @@ abstract class RenderObject extends AbstractNode with DiagnosticableTreeMixin im
     Curve curve = Curves.ease,
   }) {
     if (parent is RenderObject) {
-      final RenderObject renderParent = parent;
+      final RenderObject renderParent = parent as RenderObject;
       renderParent.showOnScreen(
         descendant: descendant ?? this,
         rect: rect,
@@ -3003,20 +3003,20 @@ mixin ContainerParentDataMixin<ChildType extends RenderObject> on ParentData {
 /// list of children.
 mixin ContainerRenderObjectMixin<ChildType extends RenderObject, ParentDataType extends ContainerParentDataMixin<ChildType>> on RenderObject {
   bool _debugUltimatePreviousSiblingOf(ChildType child, { ChildType equals }) {
-    ParentDataType childParentData = child.parentData;
+    ParentDataType childParentData = child.parentData as ParentDataType;
     while (childParentData.previousSibling != null) {
       assert(childParentData.previousSibling != child);
       child = childParentData.previousSibling;
-      childParentData = child.parentData;
+      childParentData = child.parentData as ParentDataType;
     }
     return child == equals;
   }
   bool _debugUltimateNextSiblingOf(ChildType child, { ChildType equals }) {
-    ParentDataType childParentData = child.parentData;
+    ParentDataType childParentData = child.parentData as ParentDataType;
     while (childParentData.nextSibling != null) {
       assert(childParentData.nextSibling != child);
       child = childParentData.nextSibling;
-      childParentData = child.parentData;
+      childParentData = child.parentData as ParentDataType;
     }
     return child == equals;
   }
@@ -3068,7 +3068,7 @@ mixin ContainerRenderObjectMixin<ChildType extends RenderObject, ParentDataType
   ChildType _firstChild;
   ChildType _lastChild;
   void _insertIntoChildList(ChildType child, { ChildType after }) {
-    final ParentDataType childParentData = child.parentData;
+    final ParentDataType childParentData = child.parentData as ParentDataType;
     assert(childParentData.nextSibling == null);
     assert(childParentData.previousSibling == null);
     _childCount += 1;
@@ -3077,7 +3077,7 @@ mixin ContainerRenderObjectMixin<ChildType extends RenderObject, ParentDataType
       // insert at the start (_firstChild)
       childParentData.nextSibling = _firstChild;
       if (_firstChild != null) {
-        final ParentDataType _firstChildParentData = _firstChild.parentData;
+        final ParentDataType _firstChildParentData = _firstChild.parentData as ParentDataType;
         _firstChildParentData.previousSibling = child;
       }
       _firstChild = child;
@@ -3087,7 +3087,7 @@ mixin ContainerRenderObjectMixin<ChildType extends RenderObject, ParentDataType
       assert(_lastChild != null);
       assert(_debugUltimatePreviousSiblingOf(after, equals: _firstChild));
       assert(_debugUltimateNextSiblingOf(after, equals: _lastChild));
-      final ParentDataType afterParentData = after.parentData;
+      final ParentDataType afterParentData = after.parentData as ParentDataType;
       if (afterParentData.nextSibling == null) {
         // insert at the end (_lastChild); we'll end up with two or more children
         assert(after == _lastChild);
@@ -3100,8 +3100,8 @@ mixin ContainerRenderObjectMixin<ChildType extends RenderObject, ParentDataType
         childParentData.nextSibling = afterParentData.nextSibling;
         childParentData.previousSibling = after;
         // set up links from siblings to child
-        final ParentDataType childPreviousSiblingParentData = childParentData.previousSibling.parentData;
-        final ParentDataType childNextSiblingParentData = childParentData.nextSibling.parentData;
+        final ParentDataType childPreviousSiblingParentData = childParentData.previousSibling.parentData as ParentDataType;
+        final ParentDataType childNextSiblingParentData = childParentData.nextSibling.parentData as ParentDataType;
         childPreviousSiblingParentData.nextSibling = child;
         childNextSiblingParentData.previousSibling = child;
         assert(afterParentData.nextSibling == child);
@@ -3133,7 +3133,7 @@ mixin ContainerRenderObjectMixin<ChildType extends RenderObject, ParentDataType
   }
 
   void _removeFromChildList(ChildType child) {
-    final ParentDataType childParentData = child.parentData;
+    final ParentDataType childParentData = child.parentData as ParentDataType;
     assert(_debugUltimatePreviousSiblingOf(child, equals: _firstChild));
     assert(_debugUltimateNextSiblingOf(child, equals: _lastChild));
     assert(_childCount >= 0);
@@ -3141,14 +3141,14 @@ mixin ContainerRenderObjectMixin<ChildType extends RenderObject, ParentDataType
       assert(_firstChild == child);
       _firstChild = childParentData.nextSibling;
     } else {
-      final ParentDataType childPreviousSiblingParentData = childParentData.previousSibling.parentData;
+      final ParentDataType childPreviousSiblingParentData = childParentData.previousSibling.parentData as ParentDataType;
       childPreviousSiblingParentData.nextSibling = childParentData.nextSibling;
     }
     if (childParentData.nextSibling == null) {
       assert(_lastChild == child);
       _lastChild = childParentData.previousSibling;
     } else {
-      final ParentDataType childNextSiblingParentData = childParentData.nextSibling.parentData;
+      final ParentDataType childNextSiblingParentData = childParentData.nextSibling.parentData as ParentDataType;
       childNextSiblingParentData.previousSibling = childParentData.previousSibling;
     }
     childParentData.previousSibling = null;
@@ -3170,7 +3170,7 @@ mixin ContainerRenderObjectMixin<ChildType extends RenderObject, ParentDataType
   void removeAll() {
     ChildType child = _firstChild;
     while (child != null) {
-      final ParentDataType childParentData = child.parentData;
+      final ParentDataType childParentData = child.parentData as ParentDataType;
       final ChildType next = childParentData.nextSibling;
       childParentData.previousSibling = null;
       childParentData.nextSibling = null;
@@ -3192,7 +3192,7 @@ mixin ContainerRenderObjectMixin<ChildType extends RenderObject, ParentDataType
     assert(after != this);
     assert(child != after);
     assert(child.parent == this);
-    final ParentDataType childParentData = child.parentData;
+    final ParentDataType childParentData = child.parentData as ParentDataType;
     if (childParentData.previousSibling == after)
       return;
     _removeFromChildList(child);
@@ -3206,7 +3206,7 @@ mixin ContainerRenderObjectMixin<ChildType extends RenderObject, ParentDataType
     ChildType child = _firstChild;
     while (child != null) {
       child.attach(owner);
-      final ParentDataType childParentData = child.parentData;
+      final ParentDataType childParentData = child.parentData as ParentDataType;
       child = childParentData.nextSibling;
     }
   }
@@ -3217,7 +3217,7 @@ mixin ContainerRenderObjectMixin<ChildType extends RenderObject, ParentDataType
     ChildType child = _firstChild;
     while (child != null) {
       child.detach();
-      final ParentDataType childParentData = child.parentData;
+      final ParentDataType childParentData = child.parentData as ParentDataType;
       child = childParentData.nextSibling;
     }
   }
@@ -3227,7 +3227,7 @@ mixin ContainerRenderObjectMixin<ChildType extends RenderObject, ParentDataType
     ChildType child = _firstChild;
     while (child != null) {
       redepthChild(child);
-      final ParentDataType childParentData = child.parentData;
+      final ParentDataType childParentData = child.parentData as ParentDataType;
       child = childParentData.nextSibling;
     }
   }
@@ -3237,7 +3237,7 @@ mixin ContainerRenderObjectMixin<ChildType extends RenderObject, ParentDataType
     ChildType child = _firstChild;
     while (child != null) {
       visitor(child);
-      final ParentDataType childParentData = child.parentData;
+      final ParentDataType childParentData = child.parentData as ParentDataType;
       child = childParentData.nextSibling;
     }
   }
@@ -3252,7 +3252,7 @@ mixin ContainerRenderObjectMixin<ChildType extends RenderObject, ParentDataType
   ChildType childBefore(ChildType child) {
     assert(child != null);
     assert(child.parent == this);
-    final ParentDataType childParentData = child.parentData;
+    final ParentDataType childParentData = child.parentData as ParentDataType;
     return childParentData.previousSibling;
   }
 
@@ -3260,7 +3260,7 @@ mixin ContainerRenderObjectMixin<ChildType extends RenderObject, ParentDataType
   ChildType childAfter(ChildType child) {
     assert(child != null);
     assert(child.parent == this);
-    final ParentDataType childParentData = child.parentData;
+    final ParentDataType childParentData = child.parentData as ParentDataType;
     return childParentData.nextSibling;
   }
 
@@ -3275,7 +3275,7 @@ mixin ContainerRenderObjectMixin<ChildType extends RenderObject, ParentDataType
         if (child == lastChild)
           break;
         count += 1;
-        final ParentDataType childParentData = child.parentData;
+        final ParentDataType childParentData = child.parentData as ParentDataType;
         child = childParentData.nextSibling;
       }
     }
@@ -3305,7 +3305,7 @@ mixin RelayoutWhenSystemFontsChangeMixin on RenderObject {
   }
 
   @override
-  void attach(covariant Object owner) {
+  void attach(covariant PipelineOwner owner) {
     super.attach(owner);
     PaintingBinding.instance.systemFonts.addListener(systemFontsDidChange);
   }
@@ -3834,12 +3834,12 @@ class _SemanticsGeometry {
     assert(transform != null);
     assert(clipRectTransform != null);
     assert(clipRectTransform.isIdentity());
-    RenderObject intermediateParent = child.parent;
+    RenderObject intermediateParent = child.parent as RenderObject;
     assert(intermediateParent != null);
     while (intermediateParent != ancestor) {
       intermediateParent.applyPaintTransform(child, transform);
-      intermediateParent = intermediateParent.parent;
-      child = child.parent;
+      intermediateParent = intermediateParent.parent as RenderObject;
+      child = child.parent as RenderObject;
       assert(intermediateParent != null);
     }
     ancestor.applyPaintTransform(child, transform);
diff --git a/packages/flutter/lib/src/rendering/paragraph.dart b/packages/flutter/lib/src/rendering/paragraph.dart
index 83c4ed3d20..b62cdd03e1 100644
--- a/packages/flutter/lib/src/rendering/paragraph.dart
+++ b/packages/flutter/lib/src/rendering/paragraph.dart
@@ -414,7 +414,7 @@ class RenderParagraph extends RenderBox
   bool hitTestChildren(BoxHitTestResult result, { Offset position }) {
     RenderBox child = firstChild;
     while (child != null) {
-      final TextParentData textParentData = child.parentData;
+      final TextParentData textParentData = child.parentData as TextParentData;
       final Matrix4 transform = Matrix4.translationValues(
         textParentData.offset.dx,
         textParentData.offset.dy,
@@ -458,7 +458,7 @@ class RenderParagraph extends RenderBox
     }
     if (span is TextSpan) {
       final TextSpan textSpan = span;
-      textSpan.recognizer?.addPointer(event);
+      textSpan.recognizer?.addPointer(event as PointerDownEvent);
     }
   }
 
@@ -550,7 +550,7 @@ class RenderParagraph extends RenderBox
     RenderBox child = firstChild;
     int childIndex = 0;
     while (child != null && childIndex < _textPainter.inlinePlaceholderBoxes.length) {
-      final TextParentData textParentData = child.parentData;
+      final TextParentData textParentData = child.parentData as TextParentData;
       textParentData.offset = Offset(
         _textPainter.inlinePlaceholderBoxes[childIndex].left,
         _textPainter.inlinePlaceholderBoxes[childIndex].top,
@@ -681,7 +681,7 @@ class RenderParagraph extends RenderBox
     // it until we finish layout, and RenderObject is in immutable state at
     // this point.
     while (child != null && childIndex < _textPainter.inlinePlaceholderBoxes.length) {
-      final TextParentData textParentData = child.parentData;
+      final TextParentData textParentData = child.parentData as TextParentData;
 
       final double scale = textParentData.scale;
       context.pushTransform(
@@ -876,7 +876,7 @@ class RenderParagraph extends RenderBox
 
       if (info.isPlaceholder) {
         final SemanticsNode childNode = children.elementAt(placeholderIndex++);
-        final TextParentData parentData = child.parentData;
+        final TextParentData parentData = child.parentData as TextParentData;
         childNode.rect = Rect.fromLTWH(
           childNode.rect.left,
           childNode.rect.top,
@@ -890,13 +890,12 @@ class RenderParagraph extends RenderBox
           ..sortKey = OrdinalSortKey(ordinal++)
           ..textDirection = initialDirection
           ..label = info.semanticsLabel ?? info.text;
-        if (info.recognizer != null) {
-          if (info.recognizer is TapGestureRecognizer) {
-            final TapGestureRecognizer recognizer = info.recognizer;
+        final GestureRecognizer recognizer = info.recognizer;
+        if (recognizer != null) {
+          if (recognizer is TapGestureRecognizer) {
             configuration.onTap = recognizer.onTap;
             configuration.isLink = true;
-          } else if (info.recognizer is LongPressGestureRecognizer) {
-            final LongPressGestureRecognizer recognizer = info.recognizer;
+          } else if (recognizer is LongPressGestureRecognizer) {
             configuration.onLongPress = recognizer.onLongPress;
           } else {
             assert(false);
diff --git a/packages/flutter/lib/src/rendering/platform_view.dart b/packages/flutter/lib/src/rendering/platform_view.dart
index 70778db629..5ba14ef9a3 100644
--- a/packages/flutter/lib/src/rendering/platform_view.dart
+++ b/packages/flutter/lib/src/rendering/platform_view.dart
@@ -341,7 +341,7 @@ class RenderUiKitView extends RenderBox {
     if (event is! PointerDownEvent) {
       return;
     }
-    _gestureRecognizer.addPointer(event);
+    _gestureRecognizer.addPointer(event as PointerDownEvent);
     _lastPointerDownEvent = event.original ?? event;
   }
 
diff --git a/packages/flutter/lib/src/rendering/proxy_box.dart b/packages/flutter/lib/src/rendering/proxy_box.dart
index d9f000fbbc..02d7420080 100644
--- a/packages/flutter/lib/src/rendering/proxy_box.dart
+++ b/packages/flutter/lib/src/rendering/proxy_box.dart
@@ -800,7 +800,7 @@ class RenderOpacity extends RenderProxyBox {
         return;
       }
       assert(needsCompositing);
-      layer = context.pushOpacity(offset, _alpha, super.paint, oldLayer: layer);
+      layer = context.pushOpacity(offset, _alpha, super.paint, oldLayer: layer as OpacityLayer);
     }
   }
 
@@ -920,7 +920,7 @@ class RenderAnimatedOpacity extends RenderProxyBox {
         return;
       }
       assert(needsCompositing);
-      layer = context.pushOpacity(offset, _alpha, super.paint, oldLayer: layer);
+      layer = context.pushOpacity(offset, _alpha, super.paint, oldLayer: layer as OpacityLayer);
     }
   }
 
@@ -962,7 +962,7 @@ class RenderShaderMask extends RenderProxyBox {
        super(child);
 
   @override
-  ShaderMaskLayer get layer => super.layer;
+  ShaderMaskLayer get layer => super.layer as ShaderMaskLayer;
 
   /// Called to creates the [Shader] that generates the mask.
   ///
@@ -1030,7 +1030,7 @@ class RenderBackdropFilter extends RenderProxyBox {
       super(child);
 
   @override
-  BackdropFilterLayer get layer => super.layer;
+  BackdropFilterLayer get layer => super.layer as BackdropFilterLayer;
 
   /// The image filter to apply to the existing painted content before painting
   /// the child.
@@ -1163,7 +1163,7 @@ class ShapeBorderClipper extends CustomClipper<Path> {
   bool shouldReclip(CustomClipper<Path> oldClipper) {
     if (oldClipper.runtimeType != ShapeBorderClipper)
       return true;
-    final ShapeBorderClipper typedOldClipper = oldClipper;
+    final ShapeBorderClipper typedOldClipper = oldClipper as ShapeBorderClipper;
     return typedOldClipper.shape != shape
         || typedOldClipper.textDirection != textDirection;
   }
@@ -1315,7 +1315,14 @@ class RenderClipRect extends _RenderCustomClip<Rect> {
   void paint(PaintingContext context, Offset offset) {
     if (child != null) {
       _updateClip();
-      layer = context.pushClipRect(needsCompositing, offset, _clip, super.paint, clipBehavior: clipBehavior, oldLayer: layer);
+      layer = context.pushClipRect(
+        needsCompositing,
+        offset,
+        _clip,
+        super.paint,
+        clipBehavior: clipBehavior,
+        oldLayer: layer as ClipRectLayer,
+      );
     } else {
       layer = null;
     }
@@ -1394,7 +1401,13 @@ class RenderClipRRect extends _RenderCustomClip<RRect> {
   void paint(PaintingContext context, Offset offset) {
     if (child != null) {
       _updateClip();
-      layer = context.pushClipRRect(needsCompositing, offset, _clip.outerRect, _clip, super.paint, clipBehavior: clipBehavior, oldLayer: layer);
+      layer = context.pushClipRRect(
+        needsCompositing,
+        offset,
+        _clip.outerRect,
+        _clip,
+        super.paint, clipBehavior: clipBehavior, oldLayer: layer as ClipRRectLayer,
+      );
     } else {
       layer = null;
     }
@@ -1465,7 +1478,15 @@ class RenderClipOval extends _RenderCustomClip<Rect> {
   void paint(PaintingContext context, Offset offset) {
     if (child != null) {
       _updateClip();
-      layer = context.pushClipPath(needsCompositing, offset, _clip, _getClipPath(_clip), super.paint, clipBehavior: clipBehavior, oldLayer: layer);
+      layer = context.pushClipPath(
+        needsCompositing,
+        offset,
+        _clip,
+        _getClipPath(_clip),
+        super.paint,
+        clipBehavior: clipBehavior,
+        oldLayer: layer as ClipPathLayer,
+      );
     } else {
       layer = null;
     }
@@ -1530,7 +1551,15 @@ class RenderClipPath extends _RenderCustomClip<Path> {
   void paint(PaintingContext context, Offset offset) {
     if (child != null) {
       _updateClip();
-      layer = context.pushClipPath(needsCompositing, offset, Offset.zero & size, _clip, super.paint, clipBehavior: clipBehavior, oldLayer: layer);
+      layer = context.pushClipPath(
+        needsCompositing,
+        offset,
+        Offset.zero & size,
+        _clip,
+        super.paint,
+        clipBehavior: clipBehavior,
+        oldLayer: layer as ClipPathLayer,
+      );
     } else {
       layer = null;
     }
@@ -1667,7 +1696,7 @@ class RenderPhysicalModel extends _RenderPhysicalModelBase<RRect> {
        );
 
   @override
-  PhysicalModelLayer get layer => super.layer;
+  PhysicalModelLayer get layer => super.layer as PhysicalModelLayer;
 
   /// The shape of the layer.
   ///
@@ -1809,7 +1838,7 @@ class RenderPhysicalShape extends _RenderPhysicalModelBase<Path> {
        );
 
   @override
-  PhysicalModelLayer get layer => super.layer;
+  PhysicalModelLayer get layer => super.layer as PhysicalModelLayer;
 
   @override
   Path get _defaultClip => Path()..addRect(Offset.zero & size);
@@ -2191,7 +2220,13 @@ class RenderTransform extends RenderProxyBox {
       final Matrix4 transform = _effectiveTransform;
       final Offset childOffset = MatrixUtils.getAsTranslation(transform);
       if (childOffset == null) {
-        layer = context.pushTransform(needsCompositing, offset, transform, super.paint, oldLayer: layer);
+        layer = context.pushTransform(
+          needsCompositing,
+          offset,
+          transform,
+          super.paint,
+          oldLayer: layer as TransformLayer,
+        );
       } else {
         super.paint(context, offset + childOffset);
         layer = null;
@@ -2209,7 +2244,7 @@ class RenderTransform extends RenderProxyBox {
     super.debugFillProperties(properties);
     properties.add(TransformProperty('transform matrix', _transform));
     properties.add(DiagnosticsProperty<Offset>('origin', origin));
-    properties.add(DiagnosticsProperty<Alignment>('alignment', alignment));
+    properties.add(DiagnosticsProperty<AlignmentGeometry>('alignment', alignment));
     properties.add(EnumProperty<TextDirection>('textDirection', textDirection, defaultValue: null));
     properties.add(DiagnosticsProperty<bool>('transformHitTests', transformHitTests));
   }
@@ -2339,7 +2374,7 @@ class RenderFittedBox extends RenderProxyBox {
     final Offset childOffset = MatrixUtils.getAsTranslation(_transform);
     if (childOffset == null)
       return context.pushTransform(needsCompositing, offset, _transform, super.paint,
-          oldLayer: layer is TransformLayer ? layer : null);
+          oldLayer: layer is TransformLayer ? layer as TransformLayer : null);
     else
       super.paint(context, offset + childOffset);
     return null;
@@ -2353,7 +2388,7 @@ class RenderFittedBox extends RenderProxyBox {
     if (child != null) {
       if (_hasVisualOverflow)
         layer = context.pushClipRect(needsCompositing, offset, Offset.zero & size, _paintChildWithTransform,
-            oldLayer: layer is ClipRectLayer ? layer : null);
+            oldLayer: layer is ClipRectLayer ? layer as ClipRectLayer : null);
       else
         layer = _paintChildWithTransform(context, offset);
     }
@@ -2387,7 +2422,7 @@ class RenderFittedBox extends RenderProxyBox {
   void debugFillProperties(DiagnosticPropertiesBuilder properties) {
     super.debugFillProperties(properties);
     properties.add(EnumProperty<BoxFit>('fit', fit));
-    properties.add(DiagnosticsProperty<Alignment>('alignment', alignment));
+    properties.add(DiagnosticsProperty<AlignmentGeometry>('alignment', alignment));
     properties.add(EnumProperty<TextDirection>('textDirection', textDirection, defaultValue: null));
   }
 }
@@ -2906,7 +2941,7 @@ class RenderRepaintBoundary extends RenderProxyBox {
   ///  * [dart:ui.Scene.toImage] for more information about the image returned.
   Future<ui.Image> toImage({ double pixelRatio = 1.0 }) {
     assert(!debugNeedsPaint);
-    final OffsetLayer offsetLayer = layer;
+    final OffsetLayer offsetLayer = layer as OffsetLayer;
     return offsetLayer.toImage(Offset.zero & size, pixelRatio: pixelRatio);
   }
 
@@ -4794,7 +4829,7 @@ class RenderLeaderLayer extends RenderProxyBox {
     if (layer == null) {
       layer = LeaderLayer(link: link, offset: offset);
     } else {
-      final LeaderLayer leaderLayer = layer;
+      final LeaderLayer leaderLayer = layer as LeaderLayer;
       leaderLayer
         ..link = link
         ..offset = offset;
@@ -4895,7 +4930,7 @@ class RenderFollowerLayer extends RenderProxyBox {
 
   /// The layer we created when we were last painted.
   @override
-  FollowerLayer get layer => super.layer;
+  FollowerLayer get layer => super.layer as FollowerLayer;
 
   /// Return the transform that was used in the last composition phase, if any.
   ///
diff --git a/packages/flutter/lib/src/rendering/shifted_box.dart b/packages/flutter/lib/src/rendering/shifted_box.dart
index 2ec9da1dac..e73a832673 100644
--- a/packages/flutter/lib/src/rendering/shifted_box.dart
+++ b/packages/flutter/lib/src/rendering/shifted_box.dart
@@ -54,7 +54,7 @@ abstract class RenderShiftedBox extends RenderBox with RenderObjectWithChildMixi
     if (child != null) {
       assert(!debugNeedsLayout);
       result = child.getDistanceToActualBaseline(baseline);
-      final BoxParentData childParentData = child.parentData;
+      final BoxParentData childParentData = child.parentData as BoxParentData;
       if (result != null)
         result += childParentData.offset.dy;
     } else {
@@ -66,7 +66,7 @@ abstract class RenderShiftedBox extends RenderBox with RenderObjectWithChildMixi
   @override
   void paint(PaintingContext context, Offset offset) {
     if (child != null) {
-      final BoxParentData childParentData = child.parentData;
+      final BoxParentData childParentData = child.parentData as BoxParentData;
       context.paintChild(child, childParentData.offset + offset);
     }
   }
@@ -74,7 +74,7 @@ abstract class RenderShiftedBox extends RenderBox with RenderObjectWithChildMixi
   @override
   bool hitTestChildren(BoxHitTestResult result, { Offset position }) {
     if (child != null) {
-      final BoxParentData childParentData = child.parentData;
+      final BoxParentData childParentData = child.parentData as BoxParentData;
       return result.addWithPaintOffset(
         offset: childParentData.offset,
         position: position,
@@ -204,7 +204,7 @@ class RenderPadding extends RenderShiftedBox {
     }
     final BoxConstraints innerConstraints = constraints.deflate(_resolvedPadding);
     child.layout(innerConstraints, parentUsesSize: true);
-    final BoxParentData childParentData = child.parentData;
+    final BoxParentData childParentData = child.parentData as BoxParentData;
     childParentData.offset = Offset(_resolvedPadding.left, _resolvedPadding.top);
     size = constraints.constrain(Size(
       _resolvedPadding.left + child.size.width + _resolvedPadding.right,
@@ -321,8 +321,8 @@ abstract class RenderAligningShiftedBox extends RenderShiftedBox {
     assert(child.hasSize);
     assert(hasSize);
     assert(_resolvedAlignment != null);
-    final BoxParentData childParentData = child.parentData;
-    childParentData.offset = _resolvedAlignment.alongOffset(size - child.size);
+    final BoxParentData childParentData = child.parentData as BoxParentData;
+    childParentData.offset = _resolvedAlignment.alongOffset(size - child.size as Offset);
   }
 
   @override
@@ -411,7 +411,7 @@ class RenderPositionedBox extends RenderAligningShiftedBox {
           ..strokeWidth = 1.0
           ..color = const Color(0xFFFFFF00);
         path = Path();
-        final BoxParentData childParentData = child.parentData;
+        final BoxParentData childParentData = child.parentData as BoxParentData;
         if (childParentData.offset.dy > 0.0) {
           // vertical alignment arrows
           final double headSize = math.min(childParentData.offset.dy * 0.2, 10.0);
@@ -668,7 +668,7 @@ class RenderUnconstrainedBox extends RenderAligningShiftedBox with DebugOverflow
       child.layout(childConstraints, parentUsesSize: true);
       size = constraints.constrain(child.size);
       alignChild();
-      final BoxParentData childParentData = child.parentData;
+      final BoxParentData childParentData = child.parentData as BoxParentData;
       _overflowContainerRect = Offset.zero & size;
       _overflowChildRect = childParentData.offset & child.size;
     } else {
@@ -1121,7 +1121,7 @@ class RenderCustomSingleChildLayoutBox extends RenderShiftedBox {
       final BoxConstraints childConstraints = delegate.getConstraintsForChild(constraints);
       assert(childConstraints.debugAssertIsValid(isAppliedConstraint: true));
       child.layout(childConstraints, parentUsesSize: !childConstraints.isTight);
-      final BoxParentData childParentData = child.parentData;
+      final BoxParentData childParentData = child.parentData as BoxParentData;
       childParentData.offset = delegate.getPositionForChild(size, childConstraints.isTight ? childConstraints.smallest : child.size);
     }
   }
@@ -1187,7 +1187,7 @@ class RenderBaseline extends RenderShiftedBox {
       final double childBaseline = child.getDistanceToBaseline(baselineType);
       final double actualBaseline = baseline;
       final double top = actualBaseline - childBaseline;
-      final BoxParentData childParentData = child.parentData;
+      final BoxParentData childParentData = child.parentData as BoxParentData;
       childParentData.offset = Offset(0.0, top);
       final Size childSize = child.size;
       size = constraints.constrain(Size(childSize.width, top + childSize.height));
diff --git a/packages/flutter/lib/src/rendering/sliver.dart b/packages/flutter/lib/src/rendering/sliver.dart
index 1a761d38b0..c336a6f853 100644
--- a/packages/flutter/lib/src/rendering/sliver.dart
+++ b/packages/flutter/lib/src/rendering/sliver.dart
@@ -12,6 +12,7 @@ import 'package:vector_math/vector_math_64.dart';
 import 'binding.dart';
 import 'box.dart';
 import 'debug.dart';
+import 'layer.dart';
 import 'object.dart';
 import 'viewport.dart';
 import 'viewport_offset.dart';
@@ -452,18 +453,18 @@ class SliverConstraints extends Constraints {
       return true;
     if (other is! SliverConstraints)
       return false;
-    final SliverConstraints typedOther = other;
-    assert(typedOther.debugAssertIsValid());
-    return typedOther.axisDirection == axisDirection
-        && typedOther.growthDirection == growthDirection
-        && typedOther.scrollOffset == scrollOffset
-        && typedOther.overlap == overlap
-        && typedOther.remainingPaintExtent == remainingPaintExtent
-        && typedOther.crossAxisExtent == crossAxisExtent
-        && typedOther.crossAxisDirection == crossAxisDirection
-        && typedOther.viewportMainAxisExtent == viewportMainAxisExtent
-        && typedOther.remainingCacheExtent == remainingCacheExtent
-        && typedOther.cacheOrigin == cacheOrigin;
+    assert(other is SliverConstraints && other.debugAssertIsValid());
+    return other is SliverConstraints
+        && other.axisDirection == axisDirection
+        && other.growthDirection == growthDirection
+        && other.scrollOffset == scrollOffset
+        && other.overlap == overlap
+        && other.remainingPaintExtent == remainingPaintExtent
+        && other.crossAxisExtent == crossAxisExtent
+        && other.crossAxisDirection == crossAxisDirection
+        && other.viewportMainAxisExtent == viewportMainAxisExtent
+        && other.remainingCacheExtent == remainingCacheExtent
+        && other.cacheOrigin == cacheOrigin;
   }
 
   @override
@@ -870,7 +871,7 @@ class SliverHitTestEntry extends HitTestEntry {
        super(target);
 
   @override
-  RenderSliver get target => super.target;
+  RenderSliver get target => super.target as RenderSliver;
 
   /// The distance in the [AxisDirection] from the edge of the sliver's painted
   /// area (as given by the [SliverConstraints.scrollOffset]) to the hit point.
@@ -1110,7 +1111,7 @@ List<DiagnosticsNode> _debugCompareFloats(String labelA, double valueA, String l
 abstract class RenderSliver extends RenderObject {
   // layout input
   @override
-  SliverConstraints get constraints => super.constraints;
+  SliverConstraints get constraints => super.constraints as SliverConstraints;
 
   /// The amount of space this sliver occupies.
   ///
@@ -1327,7 +1328,7 @@ abstract class RenderSliver extends RenderObject {
     final double a = constraints.scrollOffset;
     final double b = constraints.scrollOffset + constraints.remainingPaintExtent;
     // the clamp on the next line is to avoid floating point rounding errors
-    return (to.clamp(a, b) - from.clamp(a, b)).clamp(0.0, constraints.remainingPaintExtent);
+    return (to.clamp(a, b) - from.clamp(a, b)).clamp(0.0, constraints.remainingPaintExtent) as double;
   }
 
   /// Computes the portion of the region from `from` to `to` that is within
@@ -1343,7 +1344,7 @@ abstract class RenderSliver extends RenderObject {
     final double a = constraints.scrollOffset + constraints.cacheOrigin;
     final double b = constraints.scrollOffset + constraints.remainingCacheExtent;
     // the clamp on the next line is to avoid floating point rounding errors
-    return (to.clamp(a, b) - from.clamp(a, b)).clamp(0.0, constraints.remainingCacheExtent);
+    return (to.clamp(a, b) - from.clamp(a, b)).clamp(0.0, constraints.remainingCacheExtent) as double;
   }
 
   /// Returns the distance from the leading _visible_ edge of the sliver to the
@@ -1719,7 +1720,7 @@ abstract class RenderSliverSingleBoxAdapter extends RenderSliver with RenderObje
   /// [SliverConstraints.growthDirection] and the given geometry.
   @protected
   void setChildParentData(RenderObject child, SliverConstraints constraints, SliverGeometry geometry) {
-    final SliverPhysicalParentData childParentData = child.parentData;
+    final SliverPhysicalParentData childParentData = child.parentData as SliverPhysicalParentData;
     assert(constraints.axisDirection != null);
     assert(constraints.growthDirection != null);
     switch (applyGrowthDirectionToAxisDirection(constraints.axisDirection, constraints.growthDirection)) {
@@ -1756,14 +1757,14 @@ abstract class RenderSliverSingleBoxAdapter extends RenderSliver with RenderObje
   void applyPaintTransform(RenderObject child, Matrix4 transform) {
     assert(child != null);
     assert(child == this.child);
-    final SliverPhysicalParentData childParentData = child.parentData;
+    final SliverPhysicalParentData childParentData = child.parentData as SliverPhysicalParentData;
     childParentData.applyPaintTransform(transform);
   }
 
   @override
   void paint(PaintingContext context, Offset offset) {
     if (child != null && geometry.visible) {
-      final SliverPhysicalParentData childParentData = child.parentData;
+      final SliverPhysicalParentData childParentData = child.parentData as SliverPhysicalParentData;
       context.paintChild(child, offset + childParentData.paintOffset);
     }
   }
@@ -1945,7 +1946,7 @@ class RenderSliverOpacity extends RenderSliver with RenderObjectWithChildMixin<R
         offset,
         _alpha,
         _paintWithOpacity,
-        oldLayer: layer,
+        oldLayer: layer as OpacityLayer,
       );
     }
   }
@@ -1953,7 +1954,7 @@ class RenderSliverOpacity extends RenderSliver with RenderObjectWithChildMixin<R
   @override
   void applyPaintTransform(RenderObject child, Matrix4 transform) {
     assert(child != null);
-    final SliverPhysicalParentData childParentData = child.parentData;
+    final SliverPhysicalParentData childParentData = child.parentData as SliverPhysicalParentData;
     childParentData.applyPaintTransform(transform);
   }
 
@@ -2067,7 +2068,7 @@ class RenderSliverIgnorePointer extends RenderSliver with RenderObjectWithChildM
   @override
   void applyPaintTransform(RenderObject child, Matrix4 transform) {
     assert(child != null);
-    final SliverPhysicalParentData childParentData = child.parentData;
+    final SliverPhysicalParentData childParentData = child.parentData as SliverPhysicalParentData;
     childParentData.applyPaintTransform(transform);
   }
 
@@ -2174,7 +2175,7 @@ class RenderSliverOffstage extends RenderSliver with RenderObjectWithChildMixin<
   @override
   void applyPaintTransform(RenderObject child, Matrix4 transform) {
     assert(child != null);
-    final SliverPhysicalParentData childParentData = child.parentData;
+    final SliverPhysicalParentData childParentData = child.parentData as SliverPhysicalParentData;
     childParentData.applyPaintTransform(transform);
   }
 
diff --git a/packages/flutter/lib/src/rendering/sliver_fixed_extent_list.dart b/packages/flutter/lib/src/rendering/sliver_fixed_extent_list.dart
index 44c5f7d938..ae40e4764b 100644
--- a/packages/flutter/lib/src/rendering/sliver_fixed_extent_list.dart
+++ b/packages/flutter/lib/src/rendering/sliver_fixed_extent_list.dart
@@ -235,7 +235,7 @@ abstract class RenderSliverFixedExtentBoxAdaptor extends RenderSliverMultiBoxAda
         geometry = SliverGeometry(scrollOffsetCorrection: index * itemExtent);
         return;
       }
-      final SliverMultiBoxAdaptorParentData childParentData = child.parentData;
+      final SliverMultiBoxAdaptorParentData childParentData = child.parentData as SliverMultiBoxAdaptorParentData;
       childParentData.layoutOffset = indexToLayoutOffset(itemExtent, index);
       assert(childParentData.index == index);
       trailingChildWithLayout ??= child;
@@ -243,7 +243,7 @@ abstract class RenderSliverFixedExtentBoxAdaptor extends RenderSliverMultiBoxAda
 
     if (trailingChildWithLayout == null) {
       firstChild.layout(childConstraints);
-      final SliverMultiBoxAdaptorParentData childParentData = firstChild.parentData;
+      final SliverMultiBoxAdaptorParentData childParentData = firstChild.parentData as SliverMultiBoxAdaptorParentData;
       childParentData.layoutOffset = indexToLayoutOffset(itemExtent, firstIndex);
       trailingChildWithLayout = firstChild;
     }
@@ -263,7 +263,7 @@ abstract class RenderSliverFixedExtentBoxAdaptor extends RenderSliverMultiBoxAda
       }
       trailingChildWithLayout = child;
       assert(child != null);
-      final SliverMultiBoxAdaptorParentData childParentData = child.parentData;
+      final SliverMultiBoxAdaptorParentData childParentData = child.parentData as SliverMultiBoxAdaptorParentData;
       assert(childParentData.index == index);
       childParentData.layoutOffset = indexToLayoutOffset(itemExtent, childParentData.index);
     }
diff --git a/packages/flutter/lib/src/rendering/sliver_grid.dart b/packages/flutter/lib/src/rendering/sliver_grid.dart
index 9a2daa18ee..0cb72b8fa6 100644
--- a/packages/flutter/lib/src/rendering/sliver_grid.dart
+++ b/packages/flutter/lib/src/rendering/sliver_grid.dart
@@ -504,7 +504,7 @@ class RenderSliverGrid extends RenderSliverMultiBoxAdaptor {
 
   @override
   double childCrossAxisPosition(RenderBox child) {
-    final SliverGridParentData childParentData = child.parentData;
+    final SliverGridParentData childParentData = child.parentData as SliverGridParentData;
     return childParentData.crossAxisOffset;
   }
 
@@ -528,8 +528,10 @@ class RenderSliverGrid extends RenderSliverMultiBoxAdaptor {
     if (firstChild != null) {
       final int oldFirstIndex = indexOf(firstChild);
       final int oldLastIndex = indexOf(lastChild);
-      final int leadingGarbage = (firstIndex - oldFirstIndex).clamp(0, childCount);
-      final int trailingGarbage = targetLastIndex == null ? 0 : (oldLastIndex - targetLastIndex).clamp(0, childCount);
+      final int leadingGarbage = (firstIndex - oldFirstIndex).clamp(0, childCount) as int;
+      final int trailingGarbage = targetLastIndex == null
+        ? 0
+        : ((oldLastIndex - targetLastIndex).clamp(0, childCount) as int);
       collectGarbage(leadingGarbage, trailingGarbage);
     } else {
       collectGarbage(0, 0);
@@ -559,7 +561,7 @@ class RenderSliverGrid extends RenderSliverMultiBoxAdaptor {
       final RenderBox child = insertAndLayoutLeadingChild(
         gridGeometry.getBoxConstraints(constraints),
       );
-      final SliverGridParentData childParentData = child.parentData;
+      final SliverGridParentData childParentData = child.parentData as SliverGridParentData;
       childParentData.layoutOffset = gridGeometry.scrollOffset;
       childParentData.crossAxisOffset = gridGeometry.crossAxisOffset;
       assert(childParentData.index == index);
@@ -569,7 +571,7 @@ class RenderSliverGrid extends RenderSliverMultiBoxAdaptor {
 
     if (trailingChildWithLayout == null) {
       firstChild.layout(firstChildGridGeometry.getBoxConstraints(constraints));
-      final SliverGridParentData childParentData = firstChild.parentData;
+      final SliverGridParentData childParentData = firstChild.parentData as SliverGridParentData;
       childParentData.layoutOffset = firstChildGridGeometry.scrollOffset;
       childParentData.crossAxisOffset = firstChildGridGeometry.crossAxisOffset;
       trailingChildWithLayout = firstChild;
@@ -590,7 +592,7 @@ class RenderSliverGrid extends RenderSliverMultiBoxAdaptor {
       }
       trailingChildWithLayout = child;
       assert(child != null);
-      final SliverGridParentData childParentData = child.parentData;
+      final SliverGridParentData childParentData = child.parentData as SliverGridParentData;
       childParentData.layoutOffset = gridGeometry.scrollOffset;
       childParentData.crossAxisOffset = gridGeometry.crossAxisOffset;
       assert(childParentData.index == index);
diff --git a/packages/flutter/lib/src/rendering/sliver_list.dart b/packages/flutter/lib/src/rendering/sliver_list.dart
index 5f25e1ccbc..a8e8801a5b 100644
--- a/packages/flutter/lib/src/rendering/sliver_list.dart
+++ b/packages/flutter/lib/src/rendering/sliver_list.dart
@@ -99,7 +99,7 @@ class RenderSliverList extends RenderSliverMultiBoxAdaptor {
       earliestUsefulChild = insertAndLayoutLeadingChild(childConstraints, parentUsesSize: true);
 
       if (earliestUsefulChild == null) {
-        final SliverMultiBoxAdaptorParentData childParentData = firstChild.parentData;
+        final SliverMultiBoxAdaptorParentData childParentData = firstChild.parentData as SliverMultiBoxAdaptorParentData;
         childParentData.layoutOffset = 0.0;
 
         if (scrollOffset == 0.0) {
@@ -142,12 +142,12 @@ class RenderSliverList extends RenderSliverMultiBoxAdaptor {
         geometry = SliverGeometry(
           scrollOffsetCorrection: correction - earliestScrollOffset,
         );
-        final SliverMultiBoxAdaptorParentData childParentData = firstChild.parentData;
+        final SliverMultiBoxAdaptorParentData childParentData = firstChild.parentData as SliverMultiBoxAdaptorParentData;
         childParentData.layoutOffset = 0.0;
         return;
       }
 
-      final SliverMultiBoxAdaptorParentData childParentData = earliestUsefulChild.parentData;
+      final SliverMultiBoxAdaptorParentData childParentData = earliestUsefulChild.parentData as SliverMultiBoxAdaptorParentData;
       childParentData.layoutOffset = firstChildScrollOffset;
       assert(earliestUsefulChild == firstChild);
       leadingChildWithLayout = earliestUsefulChild;
@@ -207,7 +207,7 @@ class RenderSliverList extends RenderSliverMultiBoxAdaptor {
         trailingChildWithLayout = child;
       }
       assert(child != null);
-      final SliverMultiBoxAdaptorParentData childParentData = child.parentData;
+      final SliverMultiBoxAdaptorParentData childParentData = child.parentData as SliverMultiBoxAdaptorParentData;
       childParentData.layoutOffset = endScrollOffset;
       assert(childParentData.index == index);
       endScrollOffset = childScrollOffset(child) + paintExtentOf(child);
diff --git a/packages/flutter/lib/src/rendering/sliver_multi_box_adaptor.dart b/packages/flutter/lib/src/rendering/sliver_multi_box_adaptor.dart
index ad38d5cff0..becf10eeed 100644
--- a/packages/flutter/lib/src/rendering/sliver_multi_box_adaptor.dart
+++ b/packages/flutter/lib/src/rendering/sliver_multi_box_adaptor.dart
@@ -243,9 +243,9 @@ abstract class RenderSliverMultiBoxAdaptor extends RenderSliver
   @override
   void adoptChild(RenderObject child) {
     super.adoptChild(child);
-    final SliverMultiBoxAdaptorParentData childParentData = child.parentData;
+    final SliverMultiBoxAdaptorParentData childParentData = child.parentData as SliverMultiBoxAdaptorParentData;
     if (!childParentData._keptAlive)
-      childManager.didAdoptChild(child);
+      childManager.didAdoptChild(child as RenderBox);
   }
 
   bool _debugAssertChildListLocked() => childManager.debugAssertChildListLocked();
@@ -285,7 +285,7 @@ abstract class RenderSliverMultiBoxAdaptor extends RenderSliver
     // 2. The child is keptAlive.
     // In this case, the child is no longer in the childList but might be stored in
     // [_keepAliveBucket]. We need to update the location of the child in the bucket.
-    final SliverMultiBoxAdaptorParentData childParentData = child.parentData;
+    final SliverMultiBoxAdaptorParentData childParentData = child.parentData as SliverMultiBoxAdaptorParentData;
     if (!childParentData.keptAlive) {
       super.move(child, after: after);
       childManager.didAdoptChild(child); // updates the slot in the parentData
@@ -318,7 +318,7 @@ abstract class RenderSliverMultiBoxAdaptor extends RenderSliver
 
   @override
   void remove(RenderBox child) {
-    final SliverMultiBoxAdaptorParentData childParentData = child.parentData;
+    final SliverMultiBoxAdaptorParentData childParentData = child.parentData as SliverMultiBoxAdaptorParentData;
     if (!childParentData._keptAlive) {
       super.remove(child);
       return;
@@ -344,7 +344,7 @@ abstract class RenderSliverMultiBoxAdaptor extends RenderSliver
       assert(constraints == this.constraints);
       if (_keepAliveBucket.containsKey(index)) {
         final RenderBox child = _keepAliveBucket.remove(index);
-        final SliverMultiBoxAdaptorParentData childParentData = child.parentData;
+        final SliverMultiBoxAdaptorParentData childParentData = child.parentData as SliverMultiBoxAdaptorParentData;
         assert(childParentData._keptAlive);
         dropChild(child);
         child.parentData = childParentData;
@@ -357,7 +357,7 @@ abstract class RenderSliverMultiBoxAdaptor extends RenderSliver
   }
 
   void _destroyOrCacheChild(RenderBox child) {
-    final SliverMultiBoxAdaptorParentData childParentData = child.parentData;
+    final SliverMultiBoxAdaptorParentData childParentData = child.parentData as SliverMultiBoxAdaptorParentData;
     if (childParentData.keepAlive) {
       assert(!childParentData._keptAlive);
       remove(child);
@@ -428,7 +428,7 @@ abstract class RenderSliverMultiBoxAdaptor extends RenderSliver
     if (firstChild != null) {
       assert(firstChild == lastChild);
       assert(indexOf(firstChild) == index);
-      final SliverMultiBoxAdaptorParentData firstChildParentData = firstChild.parentData;
+      final SliverMultiBoxAdaptorParentData firstChildParentData = firstChild.parentData as SliverMultiBoxAdaptorParentData;
       firstChildParentData.layoutOffset = layoutOffset;
       return true;
     }
@@ -522,11 +522,11 @@ abstract class RenderSliverMultiBoxAdaptor extends RenderSliver
       // kept alive. (This should cause _keepAliveBucket to change, so we have
       // to prepare our list ahead of time.)
       _keepAliveBucket.values.where((RenderBox child) {
-        final SliverMultiBoxAdaptorParentData childParentData = child.parentData;
+        final SliverMultiBoxAdaptorParentData childParentData = child.parentData as SliverMultiBoxAdaptorParentData;
         return !childParentData.keepAlive;
       }).toList().forEach(_childManager.removeChild);
       assert(_keepAliveBucket.values.where((RenderBox child) {
-        final SliverMultiBoxAdaptorParentData childParentData = child.parentData;
+        final SliverMultiBoxAdaptorParentData childParentData = child.parentData as SliverMultiBoxAdaptorParentData;
         return !childParentData.keepAlive;
       }).isEmpty);
     });
@@ -536,7 +536,7 @@ abstract class RenderSliverMultiBoxAdaptor extends RenderSliver
   /// [SliverMultiBoxAdaptorParentData.index] field of the child's [parentData].
   int indexOf(RenderBox child) {
     assert(child != null);
-    final SliverMultiBoxAdaptorParentData childParentData = child.parentData;
+    final SliverMultiBoxAdaptorParentData childParentData = child.parentData as SliverMultiBoxAdaptorParentData;
     assert(childParentData.index != null);
     return childParentData.index;
   }
@@ -577,14 +577,14 @@ abstract class RenderSliverMultiBoxAdaptor extends RenderSliver
   double childScrollOffset(RenderObject child) {
     assert(child != null);
     assert(child.parent == this);
-    final SliverMultiBoxAdaptorParentData childParentData = child.parentData;
+    final SliverMultiBoxAdaptorParentData childParentData = child.parentData as SliverMultiBoxAdaptorParentData;
     assert(childParentData.layoutOffset != null);
     return childParentData.layoutOffset;
   }
 
   @override
   void applyPaintTransform(RenderObject child, Matrix4 transform) {
-    applyPaintTransformForBoxChild(child, transform);
+    applyPaintTransformForBoxChild(child as RenderBox, transform);
   }
 
   @override
@@ -674,7 +674,7 @@ abstract class RenderSliverMultiBoxAdaptor extends RenderSliver
     if (firstChild != null) {
       RenderBox child = firstChild;
       while (true) {
-        final SliverMultiBoxAdaptorParentData childParentData = child.parentData;
+        final SliverMultiBoxAdaptorParentData childParentData = child.parentData as SliverMultiBoxAdaptorParentData;
         children.add(child.toDiagnosticsNode(name: 'child with index ${childParentData.index}'));
         if (child == lastChild)
           break;
diff --git a/packages/flutter/lib/src/rendering/sliver_padding.dart b/packages/flutter/lib/src/rendering/sliver_padding.dart
index 676093b43a..0a573a45a4 100644
--- a/packages/flutter/lib/src/rendering/sliver_padding.dart
+++ b/packages/flutter/lib/src/rendering/sliver_padding.dart
@@ -188,7 +188,7 @@ abstract class RenderSliverEdgeInsetsPadding extends RenderSliver with RenderObj
       hasVisualOverflow: childLayoutGeometry.hasVisualOverflow,
     );
 
-    final SliverPhysicalParentData childParentData = child.parentData;
+    final SliverPhysicalParentData childParentData = child.parentData as SliverPhysicalParentData;
     assert(constraints.axisDirection != null);
     assert(constraints.growthDirection != null);
     switch (applyGrowthDirectionToAxisDirection(constraints.axisDirection, constraints.growthDirection)) {
@@ -215,7 +215,7 @@ abstract class RenderSliverEdgeInsetsPadding extends RenderSliver with RenderObj
   @override
   bool hitTestChildren(SliverHitTestResult result, { @required double mainAxisPosition, @required double crossAxisPosition }) {
     if (child != null && child.geometry.hitTestExtent > 0.0) {
-      final SliverPhysicalParentData childParentData = child.parentData;
+      final SliverPhysicalParentData childParentData = child.parentData as SliverPhysicalParentData;
       result.addWithAxisOffset(
         mainAxisPosition: mainAxisPosition,
         crossAxisPosition: crossAxisPosition,
@@ -264,14 +264,14 @@ abstract class RenderSliverEdgeInsetsPadding extends RenderSliver with RenderObj
   void applyPaintTransform(RenderObject child, Matrix4 transform) {
     assert(child != null);
     assert(child == this.child);
-    final SliverPhysicalParentData childParentData = child.parentData;
+    final SliverPhysicalParentData childParentData = child.parentData as SliverPhysicalParentData;
     childParentData.applyPaintTransform(transform);
   }
 
   @override
   void paint(PaintingContext context, Offset offset) {
     if (child != null && child.geometry.visible) {
-      final SliverPhysicalParentData childParentData = child.parentData;
+      final SliverPhysicalParentData childParentData = child.parentData as SliverPhysicalParentData;
       context.paintChild(child, offset + childParentData.paintOffset);
     }
   }
@@ -287,7 +287,7 @@ abstract class RenderSliverEdgeInsetsPadding extends RenderSliver with RenderObj
         Rect innerRect;
         if (child != null) {
           childSize = child.getAbsoluteSize();
-          final SliverPhysicalParentData childParentData = child.parentData;
+          final SliverPhysicalParentData childParentData = child.parentData as SliverPhysicalParentData;
           innerRect = (offset + childParentData.paintOffset) & childSize;
           assert(innerRect.top >= outerRect.top);
           assert(innerRect.left >= outerRect.left);
diff --git a/packages/flutter/lib/src/rendering/sliver_persistent_header.dart b/packages/flutter/lib/src/rendering/sliver_persistent_header.dart
index 5063742b72..aebfce1b15 100644
--- a/packages/flutter/lib/src/rendering/sliver_persistent_header.dart
+++ b/packages/flutter/lib/src/rendering/sliver_persistent_header.dart
@@ -231,7 +231,7 @@ abstract class RenderSliverPersistentHeader extends RenderSliver with RenderObje
   void applyPaintTransform(RenderObject child, Matrix4 transform) {
     assert(child != null);
     assert(child == this.child);
-    applyPaintTransformForBoxChild(child, transform);
+    applyPaintTransformForBoxChild(child as RenderBox, transform);
   }
 
   @override
@@ -321,7 +321,7 @@ abstract class RenderSliverScrollingPersistentHeader extends RenderSliverPersist
     geometry = SliverGeometry(
       scrollExtent: maxExtent,
       paintOrigin: math.min(constraints.overlap, 0.0),
-      paintExtent: paintExtent.clamp(0.0, constraints.remainingPaintExtent),
+      paintExtent: paintExtent.clamp(0.0, constraints.remainingPaintExtent) as double,
       maxPaintExtent: maxExtent + stretchOffset,
       hasVisualOverflow: true, // Conservatively say we do have overflow to avoid complexity.
     );
@@ -337,7 +337,7 @@ abstract class RenderSliverScrollingPersistentHeader extends RenderSliverPersist
     geometry = SliverGeometry(
       scrollExtent: maxExtent,
       paintOrigin: math.min(constraints.overlap, 0.0),
-      paintExtent: paintExtent.clamp(0.0, constraints.remainingPaintExtent),
+      paintExtent: paintExtent.clamp(0.0, constraints.remainingPaintExtent) as double,
       maxPaintExtent: maxExtent,
       hasVisualOverflow: true, // Conservatively say we do have overflow to avoid complexity.
     );
@@ -373,7 +373,7 @@ abstract class RenderSliverPinnedPersistentHeader extends RenderSliverPersistent
     final bool overlapsContent = constraints.overlap > 0.0;
     excludeFromSemanticsScrolling = overlapsContent || (constraints.scrollOffset > maxExtent - minExtent);
     layoutChild(constraints.scrollOffset, maxExtent, overlapsContent: overlapsContent);
-    final double layoutExtent = (maxExtent - constraints.scrollOffset).clamp(0.0, constraints.remainingPaintExtent);
+    final double layoutExtent = (maxExtent - constraints.scrollOffset).clamp(0.0, constraints.remainingPaintExtent) as double;
     final double stretchOffset = stretchConfiguration != null ?
       constraints.overlap.abs() :
       0.0;
@@ -505,8 +505,8 @@ abstract class RenderSliverFloatingPersistentHeader extends RenderSliverPersiste
     geometry = SliverGeometry(
       scrollExtent: maxExtent,
       paintOrigin: math.min(constraints.overlap, 0.0),
-      paintExtent: paintExtent.clamp(0.0, constraints.remainingPaintExtent),
-      layoutExtent: layoutExtent.clamp(0.0, constraints.remainingPaintExtent),
+      paintExtent: paintExtent.clamp(0.0, constraints.remainingPaintExtent) as double,
+      layoutExtent: layoutExtent.clamp(0.0, constraints.remainingPaintExtent) as double,
       maxPaintExtent: maxExtent + stretchOffset,
       hasVisualOverflow: true, // Conservatively say we do have overflow to avoid complexity.
     );
@@ -565,7 +565,7 @@ abstract class RenderSliverFloatingPersistentHeader extends RenderSliverPersiste
         if (delta > 0.0) // If we are trying to expand when allowFloatingExpansion is false,
           delta = 0.0; // disallow the expansion. (But allow shrinking, i.e. delta < 0.0 is fine.)
       }
-      _effectiveScrollOffset = (_effectiveScrollOffset - delta).clamp(0.0, constraints.scrollOffset);
+      _effectiveScrollOffset = (_effectiveScrollOffset - delta).clamp(0.0, constraints.scrollOffset) as double;
     } else {
       _effectiveScrollOffset = constraints.scrollOffset;
     }
@@ -627,7 +627,7 @@ abstract class RenderSliverFloatingPinnedPersistentHeader extends RenderSliverFl
     final double clampedPaintExtent = paintExtent.clamp(
       minAllowedExtent,
       constraints.remainingPaintExtent,
-    );
+    ) as double;
     final double layoutExtent = maxExtent - constraints.scrollOffset;
     final double stretchOffset = stretchConfiguration != null ?
       constraints.overlap.abs() :
@@ -636,7 +636,7 @@ abstract class RenderSliverFloatingPinnedPersistentHeader extends RenderSliverFl
       scrollExtent: maxExtent,
       paintOrigin: math.min(constraints.overlap, 0.0),
       paintExtent: clampedPaintExtent,
-      layoutExtent: layoutExtent.clamp(0.0, clampedPaintExtent),
+      layoutExtent: layoutExtent.clamp(0.0, clampedPaintExtent) as double,
       maxPaintExtent: maxExtent + stretchOffset,
       maxScrollObstructionExtent: maxExtent,
       hasVisualOverflow: true, // Conservatively say we do have overflow to avoid complexity.
diff --git a/packages/flutter/lib/src/rendering/stack.dart b/packages/flutter/lib/src/rendering/stack.dart
index 1b02c60dd7..75f334f01e 100644
--- a/packages/flutter/lib/src/rendering/stack.dart
+++ b/packages/flutter/lib/src/rendering/stack.dart
@@ -154,13 +154,11 @@ class RelativeRect {
   bool operator ==(dynamic other) {
     if (identical(this, other))
       return true;
-    if (other is! RelativeRect)
-      return false;
-    final RelativeRect typedOther = other;
-    return left == typedOther.left &&
-           top == typedOther.top &&
-           right == typedOther.right &&
-           bottom == typedOther.bottom;
+    return other is RelativeRect
+        && other.left == left
+        && other.top == top
+        && other.right == right
+        && other.bottom == bottom;
   }
 
   @override
@@ -431,7 +429,7 @@ class RenderStack extends RenderBox
     double extent = 0.0;
     RenderBox child = firstChild;
     while (child != null) {
-      final StackParentData childParentData = child.parentData;
+      final StackParentData childParentData = child.parentData as StackParentData;
       if (!childParentData.isPositioned)
         extent = math.max(extent, mainChildSizeGetter(child));
       assert(child.parentData == childParentData);
@@ -497,7 +495,7 @@ class RenderStack extends RenderBox
 
     RenderBox child = firstChild;
     while (child != null) {
-      final StackParentData childParentData = child.parentData;
+      final StackParentData childParentData = child.parentData as StackParentData;
 
       if (!childParentData.isPositioned) {
         hasNonPositionedChildren = true;
@@ -524,10 +522,10 @@ class RenderStack extends RenderBox
 
     child = firstChild;
     while (child != null) {
-      final StackParentData childParentData = child.parentData;
+      final StackParentData childParentData = child.parentData as StackParentData;
 
       if (!childParentData.isPositioned) {
-        childParentData.offset = _resolvedAlignment.alongOffset(size - child.size);
+        childParentData.offset = _resolvedAlignment.alongOffset(size - child.size as Offset);
       } else {
         BoxConstraints childConstraints = const BoxConstraints();
 
@@ -549,7 +547,7 @@ class RenderStack extends RenderBox
         } else if (childParentData.right != null) {
           x = size.width - childParentData.right - child.size.width;
         } else {
-          x = _resolvedAlignment.alongOffset(size - child.size).dx;
+          x = _resolvedAlignment.alongOffset(size - child.size as Offset).dx;
         }
 
         if (x < 0.0 || x + child.size.width > size.width)
@@ -561,7 +559,7 @@ class RenderStack extends RenderBox
         } else if (childParentData.bottom != null) {
           y = size.height - childParentData.bottom - child.size.height;
         } else {
-          y = _resolvedAlignment.alongOffset(size - child.size).dy;
+          y = _resolvedAlignment.alongOffset(size - child.size as Offset).dy;
         }
 
         if (y < 0.0 || y + child.size.height > size.height)
@@ -653,7 +651,7 @@ class RenderIndexedStack extends RenderStack {
     RenderBox child = firstChild;
     int i = 0;
     while (child != null && i < index) {
-      final StackParentData childParentData = child.parentData;
+      final StackParentData childParentData = child.parentData as StackParentData;
       child = childParentData.nextSibling;
       i += 1;
     }
@@ -668,7 +666,7 @@ class RenderIndexedStack extends RenderStack {
       return false;
     assert(position != null);
     final RenderBox child = _childAtIndex();
-    final StackParentData childParentData = child.parentData;
+    final StackParentData childParentData = child.parentData as StackParentData;
     return result.addWithPaintOffset(
       offset: childParentData.offset,
       position: position,
@@ -684,7 +682,7 @@ class RenderIndexedStack extends RenderStack {
     if (firstChild == null || index == null)
       return;
     final RenderBox child = _childAtIndex();
-    final StackParentData childParentData = child.parentData;
+    final StackParentData childParentData = child.parentData as StackParentData;
     context.paintChild(child, childParentData.offset + offset);
   }
 
diff --git a/packages/flutter/lib/src/rendering/table.dart b/packages/flutter/lib/src/rendering/table.dart
index fa99c829c1..12913ae369 100644
--- a/packages/flutter/lib/src/rendering/table.dart
+++ b/packages/flutter/lib/src/rendering/table.dart
@@ -1036,7 +1036,7 @@ class RenderTable extends RenderBox {
         final int xy = x + y * columns;
         final RenderBox child = _children[xy];
         if (child != null) {
-          final TableCellParentData childParentData = child.parentData;
+          final TableCellParentData childParentData = child.parentData as TableCellParentData;
           assert(childParentData != null);
           childParentData.x = x;
           childParentData.y = y;
@@ -1075,7 +1075,7 @@ class RenderTable extends RenderBox {
         final int xy = x + y * columns;
         final RenderBox child = _children[xy];
         if (child != null) {
-          final TableCellParentData childParentData = child.parentData;
+          final TableCellParentData childParentData = child.parentData as TableCellParentData;
           switch (childParentData.verticalAlignment ?? defaultVerticalAlignment) {
             case TableCellVerticalAlignment.baseline:
               if (baselines[x] != null)
@@ -1110,7 +1110,7 @@ class RenderTable extends RenderBox {
     for (int index = _children.length - 1; index >= 0; index -= 1) {
       final RenderBox child = _children[index];
       if (child != null) {
-        final BoxParentData childParentData = child.parentData;
+        final BoxParentData childParentData = child.parentData as BoxParentData;
         final bool isHit = result.addWithPaintOffset(
           offset: childParentData.offset,
           position: position,
@@ -1156,7 +1156,7 @@ class RenderTable extends RenderBox {
     for (int index = 0; index < _children.length; index += 1) {
       final RenderBox child = _children[index];
       if (child != null) {
-        final BoxParentData childParentData = child.parentData;
+        final BoxParentData childParentData = child.parentData as BoxParentData;
         context.paintChild(child, childParentData.offset + offset);
       }
     }
diff --git a/packages/flutter/lib/src/rendering/table_border.dart b/packages/flutter/lib/src/rendering/table_border.dart
index 2041a53e0e..a277440f84 100644
--- a/packages/flutter/lib/src/rendering/table_border.dart
+++ b/packages/flutter/lib/src/rendering/table_border.dart
@@ -265,13 +265,13 @@ class TableBorder {
       return true;
     if (runtimeType != other.runtimeType)
       return false;
-    final TableBorder typedOther = other;
-    return top == typedOther.top
-        && right == typedOther.right
-        && bottom == typedOther.bottom
-        && left == typedOther.left
-        && horizontalInside == typedOther.horizontalInside
-        && verticalInside == typedOther.verticalInside;
+    return other is TableBorder
+        && other.top == top
+        && other.right == right
+        && other.bottom == bottom
+        && other.left == left
+        && other.horizontalInside == horizontalInside
+        && other.verticalInside == verticalInside;
   }
 
   @override
diff --git a/packages/flutter/lib/src/rendering/view.dart b/packages/flutter/lib/src/rendering/view.dart
index d6148eb3ba..a0bc73052b 100644
--- a/packages/flutter/lib/src/rendering/view.dart
+++ b/packages/flutter/lib/src/rendering/view.dart
@@ -139,9 +139,9 @@ class RenderView extends RenderObject with RenderObjectWithChildMixin<RenderBox>
 
   Matrix4 _rootTransform;
 
-  Layer _updateMatricesAndCreateNewRootLayer() {
+  TransformLayer _updateMatricesAndCreateNewRootLayer() {
     _rootTransform = configuration.toMatrix();
-    final ContainerLayer rootLayer = TransformLayer(transform: _rootTransform);
+    final TransformLayer rootLayer = TransformLayer(transform: _rootTransform);
     rootLayer.attach(this);
     assert(_rootTransform != null);
     return rootLayer;
diff --git a/packages/flutter/lib/src/rendering/viewport.dart b/packages/flutter/lib/src/rendering/viewport.dart
index 2bb4475d8e..5c860d4fb6 100644
--- a/packages/flutter/lib/src/rendering/viewport.dart
+++ b/packages/flutter/lib/src/rendering/viewport.dart
@@ -43,7 +43,7 @@ abstract class RenderAbstractViewport extends RenderObject {
     while (object != null) {
       if (object is RenderAbstractViewport)
         return object;
-      object = object.parent;
+      object = object.parent as RenderObject;
     }
     return null;
   }
@@ -659,18 +659,18 @@ abstract class RenderViewportBase<ParentDataClass extends ContainerParentDataMix
     RenderBox pivot;
     bool onlySlivers = target is RenderSliver; // ... between viewport and `target` (`target` included).
     while (child.parent != this) {
-      assert(child.parent != null, '$target must be a descendant of $this');
+      final RenderObject parent = child.parent as RenderObject;
+      assert(parent != null, '$target must be a descendant of $this');
       if (child is RenderBox) {
         pivot = child;
       }
-      if (child.parent is RenderSliver) {
-        final RenderSliver parent = child.parent;
+      if (parent is RenderSliver) {
         leadingScrollOffset += parent.childScrollOffset(child);
       } else {
         onlySlivers = false;
         leadingScrollOffset = 0.0;
       }
-      child = child.parent;
+      child = parent;
     }
 
     if (pivot != null) {
@@ -678,7 +678,7 @@ abstract class RenderViewportBase<ParentDataClass extends ContainerParentDataMix
       assert(pivot.parent != this);
       assert(pivot != this);
       assert(pivot.parent is RenderSliver);  // TODO(abarth): Support other kinds of render objects besides slivers.
-      final RenderSliver pivotParent = pivot.parent;
+      final RenderSliver pivotParent = pivot.parent as RenderSliver;
 
       final Matrix4 transform = target.getTransformTo(pivot);
       final Rect bounds = MatrixUtils.transformRect(transform, rect);
@@ -739,7 +739,7 @@ abstract class RenderViewportBase<ParentDataClass extends ContainerParentDataMix
           break;
       }
     } else if (onlySlivers) {
-      final RenderSliver targetSliver = target;
+      final RenderSliver targetSliver = target as RenderSliver;
       targetMainAxisExtent = targetSliver.geometry.scrollExtent;
     } else {
       return RevealedOffset(offset: offset.pixels, rect: rect);
@@ -747,7 +747,7 @@ abstract class RenderViewportBase<ParentDataClass extends ContainerParentDataMix
 
     assert(child.parent == this);
     assert(child is RenderSliver);
-    final RenderSliver sliver = child;
+    final RenderSliver sliver = child as RenderSliver;
     final double extentOfPinnedSlivers = maxScrollObstructionExtentBefore(sliver);
     leadingScrollOffset = scrollOffsetOf(sliver, leadingScrollOffset);
     switch (sliver.constraints.growthDirection) {
@@ -1064,7 +1064,7 @@ abstract class RenderViewportBase<ParentDataClass extends ContainerParentDataMix
     } else {
       // `descendant` is between leading and trailing edge and hence already
       //  fully shown on screen. No action necessary.
-      final Matrix4 transform = descendant.getTransformTo(viewport.parent);
+      final Matrix4 transform = descendant.getTransformTo(viewport.parent as RenderObject);
       return MatrixUtils.transformRect(transform, rect ?? descendant.paintBounds);
     }
 
@@ -1388,8 +1388,8 @@ class RenderViewport extends RenderViewportBase<SliverPhysicalContainerParentDat
     // to the zero scroll offset (the line between the forward slivers and the
     // reverse slivers).
     final double centerOffset = mainAxisExtent * anchor - correctedOffset;
-    final double reverseDirectionRemainingPaintExtent = centerOffset.clamp(0.0, mainAxisExtent);
-    final double forwardDirectionRemainingPaintExtent = (mainAxisExtent - centerOffset).clamp(0.0, mainAxisExtent);
+    final double reverseDirectionRemainingPaintExtent = centerOffset.clamp(0.0, mainAxisExtent) as double;
+    final double forwardDirectionRemainingPaintExtent = (mainAxisExtent - centerOffset).clamp(0.0, mainAxisExtent) as double;
 
     switch (cacheExtentStyle) {
       case CacheExtentStyle.pixel:
@@ -1402,8 +1402,8 @@ class RenderViewport extends RenderViewportBase<SliverPhysicalContainerParentDat
 
     final double fullCacheExtent = mainAxisExtent + 2 * _calculatedCacheExtent;
     final double centerCacheOffset = centerOffset + _calculatedCacheExtent;
-    final double reverseDirectionRemainingCacheExtent = centerCacheOffset.clamp(0.0, fullCacheExtent);
-    final double forwardDirectionRemainingCacheExtent = (fullCacheExtent - centerCacheOffset).clamp(0.0, fullCacheExtent);
+    final double reverseDirectionRemainingCacheExtent = centerCacheOffset.clamp(0.0, fullCacheExtent) as double;
+    final double forwardDirectionRemainingCacheExtent = (fullCacheExtent - centerCacheOffset).clamp(0.0, fullCacheExtent) as double;
 
     final RenderSliver leadingNegativeChild = childBefore(center);
 
@@ -1420,7 +1420,7 @@ class RenderViewport extends RenderViewportBase<SliverPhysicalContainerParentDat
         growthDirection: GrowthDirection.reverse,
         advance: childBefore,
         remainingCacheExtent: reverseDirectionRemainingCacheExtent,
-        cacheOrigin: (mainAxisExtent - centerOffset).clamp(-_calculatedCacheExtent, 0.0),
+        cacheOrigin: (mainAxisExtent - centerOffset).clamp(-_calculatedCacheExtent, 0.0) as double,
       );
       if (result != 0.0)
         return -result;
@@ -1438,7 +1438,7 @@ class RenderViewport extends RenderViewportBase<SliverPhysicalContainerParentDat
       growthDirection: GrowthDirection.forward,
       advance: childAfter,
       remainingCacheExtent: forwardDirectionRemainingCacheExtent,
-      cacheOrigin: centerOffset.clamp(-_calculatedCacheExtent, 0.0),
+      cacheOrigin: centerOffset.clamp(-_calculatedCacheExtent, 0.0) as double,
     );
   }
 
@@ -1461,13 +1461,13 @@ class RenderViewport extends RenderViewportBase<SliverPhysicalContainerParentDat
 
   @override
   void updateChildLayoutOffset(RenderSliver child, double layoutOffset, GrowthDirection growthDirection) {
-    final SliverPhysicalParentData childParentData = child.parentData;
+    final SliverPhysicalParentData childParentData = child.parentData as SliverPhysicalParentData;
     childParentData.paintOffset = computeAbsolutePaintOffset(child, layoutOffset, growthDirection);
   }
 
   @override
   Offset paintOffsetOf(RenderSliver child) {
-    final SliverPhysicalParentData childParentData = child.parentData;
+    final SliverPhysicalParentData childParentData = child.parentData as SliverPhysicalParentData;
     return childParentData.paintOffset;
   }
 
@@ -1526,7 +1526,7 @@ class RenderViewport extends RenderViewportBase<SliverPhysicalContainerParentDat
   @override
   void applyPaintTransform(RenderObject child, Matrix4 transform) {
     assert(child != null);
-    final SliverPhysicalParentData childParentData = child.parentData;
+    final SliverPhysicalParentData childParentData = child.parentData as SliverPhysicalParentData;
     childParentData.applyPaintTransform(transform);
   }
 
@@ -1534,7 +1534,7 @@ class RenderViewport extends RenderViewportBase<SliverPhysicalContainerParentDat
   double computeChildMainAxisPosition(RenderSliver child, double parentMainAxisPosition) {
     assert(child != null);
     assert(child.constraints != null);
-    final SliverPhysicalParentData childParentData = child.parentData;
+    final SliverPhysicalParentData childParentData = child.parentData as SliverPhysicalParentData;
     switch (applyGrowthDirectionToAxisDirection(child.constraints.axisDirection, child.constraints.growthDirection)) {
       case AxisDirection.down:
         return parentMainAxisPosition - childParentData.paintOffset.dy;
@@ -1790,13 +1790,13 @@ class RenderShrinkWrappingViewport extends RenderViewportBase<SliverLogicalConta
   @override
   void updateChildLayoutOffset(RenderSliver child, double layoutOffset, GrowthDirection growthDirection) {
     assert(growthDirection == GrowthDirection.forward);
-    final SliverLogicalParentData childParentData = child.parentData;
+    final SliverLogicalParentData childParentData = child.parentData as SliverLogicalParentData;
     childParentData.layoutOffset = layoutOffset;
   }
 
   @override
   Offset paintOffsetOf(RenderSliver child) {
-    final SliverLogicalParentData childParentData = child.parentData;
+    final SliverLogicalParentData childParentData = child.parentData as SliverLogicalParentData;
     return computeAbsolutePaintOffset(child, childParentData.layoutOffset, GrowthDirection.forward);
   }
 
@@ -1829,7 +1829,7 @@ class RenderShrinkWrappingViewport extends RenderViewportBase<SliverLogicalConta
   @override
   void applyPaintTransform(RenderObject child, Matrix4 transform) {
     assert(child != null);
-    final Offset offset = paintOffsetOf(child);
+    final Offset offset = paintOffsetOf(child as RenderSliver);
     transform.translate(offset.dx, offset.dy);
   }
 
@@ -1838,7 +1838,7 @@ class RenderShrinkWrappingViewport extends RenderViewportBase<SliverLogicalConta
     assert(child != null);
     assert(child.constraints != null);
     assert(hasSize);
-    final SliverLogicalParentData childParentData = child.parentData;
+    final SliverLogicalParentData childParentData = child.parentData as SliverLogicalParentData;
     switch (applyGrowthDirectionToAxisDirection(child.constraints.axisDirection, child.constraints.growthDirection)) {
       case AxisDirection.down:
       case AxisDirection.right:
diff --git a/packages/flutter/lib/src/rendering/wrap.dart b/packages/flutter/lib/src/rendering/wrap.dart
index 0b0814086b..b0306259b1 100644
--- a/packages/flutter/lib/src/rendering/wrap.dart
+++ b/packages/flutter/lib/src/rendering/wrap.dart
@@ -623,7 +623,7 @@ class RenderWrap extends RenderBox with ContainerRenderObjectMixin<RenderBox, Wr
         runMainAxisExtent += spacing;
       runCrossAxisExtent = math.max(runCrossAxisExtent, childCrossAxisExtent);
       childCount += 1;
-      final WrapParentData childParentData = child.parentData;
+      final WrapParentData childParentData = child.parentData as WrapParentData;
       childParentData._runIndex = runMetrics.length;
       child = childParentData.nextSibling;
     }
@@ -724,7 +724,7 @@ class RenderWrap extends RenderBox with ContainerRenderObjectMixin<RenderBox, Wr
         crossAxisOffset -= runCrossAxisExtent;
 
       while (child != null) {
-        final WrapParentData childParentData = child.parentData;
+        final WrapParentData childParentData = child.parentData as WrapParentData;
         if (childParentData._runIndex != i)
           break;
         final double childMainAxisExtent = _getMainAxisExtent(child);