Typing fixes to eliminate casts/dcalls

lib/src/checker/rules.dart

Index: lib/src/checker/rules.dart
diff --git a/lib/src/checker/rules.dart b/lib/src/checker/rules.dart
index b406b9f6e930cebe06425f42cc41e4dfa6068ae9..f77f77ef4802c6b58956ba16969b48a0ba052551 100644
--- a/lib/src/checker/rules.dart
+++ b/lib/src/checker/rules.dart
@@ -613,6 +613,9 @@ class DownwardsInference {
     if (e is ConditionalExpression) {
       return _inferConditionalExpression(e, t, errors);
     }
+    if (e is ParenthesizedExpression) {
+      return _inferParenthesizedExpression(e, t, errors);
+    }
     if (e is Conversion) return _inferExpression(e.node, t, errors);
     if (rules.isSubTypeOf(rules.getStaticType(e), t)) return true;
     if (cast && rules.getStaticType(e).isDynamic) {
@@ -717,6 +720,11 @@ class DownwardsInference {
         _inferExpression(e.elseExpression, t, errors);
   }
 
+  bool _inferParenthesizedExpression(
+      ParenthesizedExpression e, DartType t, errors) {
+    return _inferExpression(e.expression, t, errors);
+  }
+
   bool _inferInstanceCreationExpression(
       InstanceCreationExpression e, DartType t, errors) {
     var arguments = e.argumentList.arguments;