Silence a bunch of annoying bogus dartanalyzer warnings.

- several places where we use a getter knowing that it will return a
   subclass of its declared type, even asserting that it does, but
   where the analyzer is worried that the getter might start returning
   a new value unexpectedly, solved by having a temporary local
   variable shadow the getter and asserting that it doesn't change
   value
 - many many places where we do this with parentData specifically,
   solved by type-erasing parentData.
 - a place where a mixin wants to be subclassing another class, and
   uses its methods, solved by saying that the mixin is abstract but
   implements the superclass

R=abarth@chromium.org

Review URL: https://codereview.chromium.org/1160923008

sdk/lib/framework/fn2.dart

@@ -336,13 +336,19 @@ abstract class OneChildRenderObjectWrapper extends RenderObjectWrapper {
   }
 
   void insert(RenderObjectWrapper child, dynamic slot) {
+    final root = this.root; // TODO(ianh): Remove this once the analyzer is cleverer
     assert(slot == null);
+    assert(root is RenderObjectWithChildMixin);
     root.child = child.root;
+    assert(root == this.root); // TODO(ianh): Remove this once the analyzer is cleverer
   }
 
   void removeChild(UINode node) {
+    final root = this.root; // TODO(ianh): Remove this once the analyzer is cleverer
+    assert(root is RenderObjectWithChildMixin);
     root.child = null;
     super.removeChild(node);
+    assert(root == this.root); // TODO(ianh): Remove this once the analyzer is cleverer
   }
 
   void remove() {
@@ -482,15 +488,19 @@ abstract class MultiChildRenderObjectWrapper extends RenderObjectWrapper {
   }
 
   void insert(RenderObjectWrapper child, dynamic slot) {
+    final root = this.root; // TODO(ianh): Remove this once the analyzer is cleverer
     assert(slot == null || slot is RenderObject);
     assert(root is ContainerRenderObjectMixin);
     root.add(child.root, before: slot);
+    assert(root == this.root); // TODO(ianh): Remove this once the analyzer is cleverer
   }
 
   void removeChild(UINode node) {
+    final root = this.root; // TODO(ianh): Remove this once the analyzer is cleverer
     assert(root is ContainerRenderObjectMixin);
     root.remove(node.root);
     super.removeChild(node);
+    assert(root == this.root); // TODO(ianh): Remove this once the analyzer is cleverer
   }
 
   void remove() {
@@ -521,6 +531,7 @@ abstract class MultiChildRenderObjectWrapper extends RenderObjectWrapper {
   void syncRenderObject(MultiChildRenderObjectWrapper old) {
     super.syncRenderObject(old);
 
+    final root = this.root; // TODO(ianh): Remove this once the analyzer is cleverer
     if (root is! ContainerRenderObjectMixin)
       return;
 
@@ -597,7 +608,7 @@ abstract class MultiChildRenderObjectWrapper extends RenderObjectWrapper {
       assert(old.root is ContainerRenderObjectMixin);
       assert(oldNode.root != null);
 
-      old.root.remove(oldNode.root);
+      (old.root as ContainerRenderObjectMixin).remove(oldNode.root); // TODO(ianh): Remove cast once the analyzer is cleverer
       root.add(oldNode.root, before: nextSibling);
 
       return true;
@@ -639,6 +650,8 @@ abstract class MultiChildRenderObjectWrapper extends RenderObjectWrapper {
       removeChild(oldNode);
       advanceOldStartIndex();
     }
+
+    assert(root == this.root); // TODO(ianh): Remove this once the analyzer is cleverer
   }
 }
 

sdk/lib/framework/rendering/object.dart

@@ -44,7 +44,7 @@ abstract class RenderObject extends AbstractNode {
   // parentData is only for use by the RenderObject that actually lays this
   // node out, and any other nodes who happen to know exactly what
   // kind of node that is.
-  ParentData parentData;
+  dynamic parentData; // TODO(ianh): change the type of this back to ParentData once the analyzer is cleverer
   void setParentData(RenderObject child) {
     // override this to setup .parentData correctly for your class
     assert(!_debugDoingLayout);
@@ -107,8 +107,10 @@ abstract class RenderObject extends AbstractNode {
     _needsLayout = true;
     assert(_relayoutSubtreeRoot != null);
     if (_relayoutSubtreeRoot != this) {
+      final parent = this.parent; // TODO(ianh): Remove this once the analyzer is cleverer
       assert(parent is RenderObject);
       parent.markNeedsLayout();
+      assert(parent == this.parent); // TODO(ianh): Remove this once the analyzer is cleverer
     } else {
       _nodesNeedingLayout.add(this);
       scheduler.ensureVisualUpdate();
@@ -136,11 +138,13 @@ abstract class RenderObject extends AbstractNode {
     _needsLayout = false;
   }
   void layout(dynamic constraints, { bool parentUsesSize: false }) {
+    final parent = this.parent; // TODO(ianh): Remove this once the analyzer is cleverer
     RenderObject relayoutSubtreeRoot;
     if (!parentUsesSize || sizedByParent || parent is! RenderObject)
       relayoutSubtreeRoot = this;
     else
       relayoutSubtreeRoot = parent._relayoutSubtreeRoot;
+    assert(parent == this.parent); // TODO(ianh): Remove this once the analyzer is cleverer
     if (!needsLayout && constraints == _constraints && relayoutSubtreeRoot == _relayoutSubtreeRoot)
       return;
     _constraints = constraints;
@@ -150,6 +154,7 @@ abstract class RenderObject extends AbstractNode {
     performLayout();
     _needsLayout = false;
     markNeedsPaint();
+    assert(parent == this.parent); // TODO(ianh): Remove this once the analyzer is cleverer
   }
   bool get sizedByParent => false; // return true if the constraints are the only input to the sizing algorithm (in particular, child nodes have no impact)
   void performResize(); // set the local dimensions, using only the constraints (only called if sizedByParent is true)
@@ -257,7 +262,7 @@ class HitTestResult {
 
 // GENERIC MIXIN FOR RENDER NODES WITH ONE CHILD
 
-abstract class RenderObjectWithChildMixin<ChildType extends RenderObject> {
+abstract class RenderObjectWithChildMixin<ChildType extends RenderObject> implements RenderObject {
   ChildType _child;
   ChildType get child => _child;
   void set child (ChildType value) {