Check for compile-time constants in DartCompiler

tests/language/src/StringInterpolate2Test.dart

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 // Dart test program testing string interpolation of expressions.
 
 
 class StringInterpolate2Test {
 
-  static final F1 = "1 + 5 = ${1+5}";
+  // String interpolation not valid on compile time constants
+  // static final F1 = "1 + 5 = ${1+5}";
 
   static void testMain() {
 
+    var F1 = "1 + 5 = ${1+5}";
+
     Expect.equals("1 + 5 = 6", F1);
 
     var fib = [1, 1, 2, 3, 5, 8, 13, 21];
 
     var i = 5;
     var s = "${i}";
     Expect.equals("5", s);
 
     s = "fib(${i}) = ${fib[i]}";
     Expect.equals("fib(5) = 8", s);
@@ skipping 19 matching lines @@
     // multiline string types
     s = "a ${(){ return 'b ${(){ return """
 c""";}()}'; }()} d";
     Expect.equals("a b c d", s);
   }
 }
 
 main() {
   StringInterpolate2Test.testMain();
 }