Use null-aware operators in package:sky

packages/flutter/lib/mojo/activity.dart

@@ -50,7 +50,7 @@ void updateTaskDescription(String label, Color color) {
 
   TaskDescription description = new TaskDescription()
     ..label = label
-    ..primaryColor = (color != null ? color.value : null);
+    ..primaryColor = color?.value;
 
   _activityProxy.ptr.setTaskDescription(description);
 }

packages/flutter/lib/src/rendering/layer.dart

@@ -242,7 +242,7 @@ class OpacityLayer extends ContainerLayer {
   int alpha;
 
   void addToScene(sky.SceneBuilder builder, Offset layerOffset) {
-    builder.pushOpacity(alpha, bounds == null ? null : bounds.shift(layerOffset));
+    builder.pushOpacity(alpha, bounds?.shift(layerOffset));
     addChildrenToScene(builder, offset + layerOffset);
     builder.pop();
   }

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

@@ -487,10 +487,7 @@ class Stack extends MultiChildRenderObjectWrapper {
   RenderStack get renderObject => super.renderObject;
 
   void updateParentData(RenderObject child, Positioned positioned) {
-    if (positioned == null)
+    _updateParentDataWithValues(child, positioned?.top, positioned?.right, positioned?.bottom, positioned?.left);
-      _updateParentDataWithValues(child, null, null, null, null);
-    else
-      _updateParentDataWithValues(child, positioned.top, positioned.right, positioned.bottom, positioned.left);
   }
 
   void _updateParentDataWithValues(RenderObject child, double top, double right, double bottom, double left) {
@@ -592,7 +589,7 @@ class Flex extends MultiChildRenderObjectWrapper {
   }
 
   void updateParentData(RenderObject child, Flexible flexible) {
-    _updateParentDataWithValues(child, flexible == null ? null : flexible.flex);
+    _updateParentDataWithValues(child, flexible?.flex);
   }
 
   void _updateParentDataWithValues(RenderObject child, int flex) {

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

@@ -21,7 +21,7 @@ class DefaultTextStyle extends Inherited {
 
   static TextStyle of(Widget widget) {
     DefaultTextStyle result = widget.inheritedOfType(DefaultTextStyle);
-    return result == null ? null : result.style;
+    return result?.style;
   }
 
   bool syncShouldNotify(DefaultTextStyle old) => style != old.style;

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

@@ -498,7 +498,7 @@ abstract class TagNode extends Widget {
   }
 
   void _sync(Widget old, dynamic slot) {
-    Widget oldChild = old == null ? null : (old as TagNode).child;
+    Widget oldChild = (old as TagNode)?.child;
     child = syncChild(child, oldChild, slot);
     if (child != null) {
       assert(child.parent == this);
@@ -1259,7 +1259,7 @@ abstract class OneChildRenderObjectWrapper extends RenderObjectWrapper {
 
   void syncRenderObject(RenderObjectWrapper old) {
     super.syncRenderObject(old);
-    Widget oldChild = old == null ? null : (old as OneChildRenderObjectWrapper).child;
+    Widget oldChild = (old as OneChildRenderObjectWrapper)?.child;
     Widget newChild = child;
     _child = syncChild(newChild, oldChild, null);
     assert((newChild == null && child == null) || (newChild != null && child.parent == this));
@@ -1304,7 +1304,7 @@ abstract class MultiChildRenderObjectWrapper extends RenderObjectWrapper {
 
   void insertChildRenderObject(RenderObjectWrapper child, Widget slot) {
     final renderObject = this.renderObject; // TODO(ianh): Remove this once the analyzer is cleverer
-    RenderObject nextSibling = slot != null ? slot.renderObject : null;
+    RenderObject nextSibling = slot?.renderObject;
     assert(nextSibling == null || nextSibling is RenderObject);
     assert(renderObject is ContainerRenderObjectMixin);
     renderObject.add(child.renderObject, before: nextSibling);

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

@@ -65,7 +65,7 @@ class HomogeneousViewport extends RenderObjectWrapper {
   }
 
   void insertChildRenderObject(RenderObjectWrapper child, Widget slot) {
-    RenderObject nextSibling = slot != null ? slot.renderObject : null;
+    RenderObject nextSibling = slot?.renderObject;
     renderObject.add(child.renderObject, before: nextSibling);
   }
 

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

@@ -31,7 +31,7 @@ class IconTheme extends Inherited {
 
   static IconThemeData of(Component component) {
     IconTheme result = component.inheritedOfType(IconTheme);
-    return result == null ? null : result.data;
+    return result?.data;
   }
 
   bool syncShouldNotify(IconTheme old) => data != old.data;

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

@@ -208,7 +208,7 @@ class Scaffold extends RenderObjectWrapper {
   }
 
   void insertChildRenderObject(RenderObjectWrapper child, ScaffoldSlots slot) {
-    renderObject[slot] = child != null ? child.renderObject : null;
+    renderObject[slot] = child?.renderObject;
   }
 
   void detachChildRenderObject(RenderObjectWrapper child) {

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

@@ -11,8 +11,6 @@ import 'package:vector_math/vector_math.dart';
 
 export 'package:sky/animation/direction.dart' show Direction;
 
-dynamic _maybe(AnimatedValue x) => x != null ? x.value : null;
-
 // A helper class to anchor widgets to one another. Pass an instance of this to
 // a Transition, then use the build() method to create a child with the same
 // transition applied.
@@ -270,7 +268,7 @@ class SquashTransition extends TransitionBase {
       performance.updateVariable(width);
     if (height != null)
       performance.updateVariable(height);
-    return new SizedBox(width: _maybe(width), height: _maybe(height), child: child);
+    return new SizedBox(width: width?.value, height: height?.value, child: child);
   }
 }
 

packages/flutter/pubspec.yaml

@@ -15,4 +15,4 @@ dependencies:
   vector_math: ^1.4.3
   intl: ^0.12.4+2
 environment:
-  sdk: '>=1.8.0 <2.0.0'
+  sdk: '>=1.12.0 <2.0.0'