Fix string_interpolation tests.

tests/language/string_interpolation6_test.dart

Index: tests/language/string_interpolation6_test.dart
diff --git a/tests/language/string_interpolation6_negative_test.dart b/tests/language/string_interpolation6_test.dart
similarity index 80%
rename from tests/language/string_interpolation6_negative_test.dart
rename to tests/language/string_interpolation6_test.dart
index e90545fc1b1faefada5133c83448dd0278c68d97..155f9fbc09f35b9cd88e51adff39ff38429aa740 100644
--- a/tests/language/string_interpolation6_negative_test.dart
+++ b/tests/language/string_interpolation6_test.dart
@@ -5,9 +5,10 @@
 // A dollar must be followed by a "{" or an identifier.
 
 class StringInterpolation6NegativeTest {
-  testMain() {
+  static testMain() {
     // Dollar not followed by "{" or identifier.
-    String regexp = "^(\\d\\d?)[-/](\\d\\d?)$";
+    String regexp;
+    regexp = "^(\\d\\d?)[-/](\\d\\d?)$"; /// 01: compile-time error
     print(regexp);
   }
 }