Add regression test for issue 20074.

tests/language/regress_20074_test.dart

Index: tests/language/regress_20074_test.dart
diff --git a/tests/language/switch_case_static_const_test.dart b/tests/language/regress_20074_test.dart
similarity index 54%
copy from tests/language/switch_case_static_const_test.dart
copy to tests/language/regress_20074_test.dart
index e15a9f46fc89414b7acb23506f4c2687cccfa36e..9b11db0e7a06f65f732692667a594dbb04dce07f 100644
--- a/tests/language/switch_case_static_const_test.dart
+++ b/tests/language/regress_20074_test.dart
@@ -2,23 +2,16 @@
 // 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.
 
-class A {
-  static const S = 'A.S';
-}
-
-const S = 'S';
+// Regression test for issue 20074. Check that a parameter is not declared
+// in the same scope as its function declaration.
 
-foo(var p) {
-  switch (p) {
-    case S:
-      break;
-    case A.S:
-      break;
-    case 'abc':
-      break;
+doit() {
+  error(error) {
+    print(error);
   }
+  error('foobar');
 }
 
 main() {
-  foo('p');
-}
+  doit();
+}