Review nits.

examples/flutter_gallery/lib/demo/calculator/logic.dart

@@ -259,9 +259,9 @@ class CalcExpression {
       case ExpressionState.NumberWithPoint:
       case ExpressionState.Result:
         return appendOperation(Operation.Subtraction);
+      default:
+        return null;
     }
-    assert(state != null);
-    return null;
   }
 
   /// Computes the result of the current expression and returns a new

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

@@ -99,7 +99,7 @@ class RaisedButton extends StatelessWidget {
       if (disabledColor != null)
         return disabledColor;
       Brightness brightness = Theme.of(context).brightness;
-      switch (Theme.of(context).brightness) {
+      switch (brightness) {
         case Brightness.light:
           return Colors.black12;
         case Brightness.dark: