Visit parenthesized expressions in compile-time constants.

frog/leg/compile_time_constants.dart

Index: frog/leg/compile_time_constants.dart
diff --git a/frog/leg/compile_time_constants.dart b/frog/leg/compile_time_constants.dart
index bee8dfaf6a812bd6fde67c4ee25ac446a7279845..b1aa8fe7d83025b2d7a9ecb51530126f1a370b74 100644
--- a/frog/leg/compile_time_constants.dart
+++ b/frog/leg/compile_time_constants.dart
@@ -693,7 +693,7 @@ class CompileTimeConstantEvaluator extends AbstractVisitor {
   }
 
   visitNode(Node node) {
-    compiler.unimplemented("CompileTimeConstantEvaluator", node: node);
+    error(node);
   }
 
   Constant visitLiteralBool(LiteralBool node) {
@@ -1056,6 +1056,10 @@ class CompileTimeConstantEvaluator extends AbstractVisitor {
     return constant;
   }
 
+  Constant visitParenthesizedExpression(ParenthesizedExpression node) {
+    return node.expression.accept(this);
+  }
+
   error(Node node) {
     // TODO(floitsch): get the list of constants that are currently compiled
     // and present some kind of stack-trace.