fix the tree (#67668)

packages/flutter/test/material/inherited_theme_test.dart

@@ -316,7 +316,7 @@ void main() {
     BorderSide dividerBorder() {
       final BoxDecoration decoration = tester.widget<Container>(
         find.descendant(of: find.byType(Divider), matching: find.byType(Container)).first,
-      ).decoration as BoxDecoration;
+      ).decoration! as BoxDecoration;
       return decoration.border!.bottom;
     }
 

packages/flutter/test/material/ink_paint_test.dart

@@ -66,7 +66,7 @@ void main() {
     await tester.pump(); // start gesture
     await tester.pump(const Duration(milliseconds: 200)); // wait for splash to be well under way
 
-    final RenderBox box = Material.of(tester.element(find.byType(InkWell))) as RenderBox;
+    final RenderBox box = Material.of(tester.element(find.byType(InkWell)))! as RenderBox;
     expect(
       box,
       paints
@@ -118,7 +118,7 @@ void main() {
     await tester.tapAt(tapDownOffset);
     await tester.pump(); // start gesture
 
-    final RenderBox box = Material.of(tester.element(find.byType(InkWell))) as RenderBox;
+    final RenderBox box = Material.of(tester.element(find.byType(InkWell)))! as RenderBox;
 
     bool offsetsAreClose(Offset a, Offset b) => (a - b).distance < 1.0;
     bool radiiAreClose(double a, double b) => (a - b).abs() < 1.0;
@@ -194,7 +194,7 @@ void main() {
     await tester.pump(); // start gesture
     await tester.pump(const Duration(milliseconds: 200)); // wait for splash to be well under way
 
-    final RenderBox box = Material.of(tester.element(find.byType(InkWell))) as RenderBox;
+    final RenderBox box = Material.of(tester.element(find.byType(InkWell)))! as RenderBox;
     expect(
       box,
       paints
@@ -326,7 +326,7 @@ void main() {
     await tester.sendKeyEvent(LogicalKeyboardKey.space);
     await tester.pump();
 
-    final RenderBox box = Material.of(tester.element(find.byType(InkWell))) as RenderBox;
+    final RenderBox box = Material.of(tester.element(find.byType(InkWell)))! as RenderBox;
 
     // ripplePattern always add a translation of topLeft.
     expect(box, ripplePattern(30.0, 0));
@@ -422,7 +422,7 @@ void main() {
     await gesture.moveTo(const Offset(0.0, 0.0));
     await gesture.up(); // generates a tap cancel
 
-    final RenderBox box = Material.of(tester.element(find.byType(InkWell))) as RenderBox;
+    final RenderBox box = Material.of(tester.element(find.byType(InkWell)))! as RenderBox;
     expect(box, paints..everything((Symbol method, List<dynamic> arguments) {
       if (method != #drawCircle)
         return true;