Detect total switches to prevent type pollution by default cases.

tests/compiler/dart2js/switch_empty_default_test.dart

+// Copyright (c) 2014, 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.
+// Test constant folding on numbers.
+
+import "package:expect/expect.dart";
+import 'compiler_helper.dart';
+
+const String SIMPLY_EMPTY = """
+int foo(x) => x;
+void main() {
+  var a = foo(4);
+  var b = 1;
+  switch (a) {
+    case 1:
+      b += 2;
+      a = 0;
+  }
+  print(a);
+}
+""";
+
+const String TOTAL = """
+void main() {
+  for (int a = 0; a < 3; a++) {
+    switch (a) {
+      case 0:
+        a = 99;
+        break;
+      case 1:
+        a = 2;
+        break;
+      case 2:
+        a = 1;
+        break;
+      default:
+        a = 33;
+    }
+  }
+  print(a);
+}
+""";
+
+const String OPTIMIZED = """
+void main() {
+  var b;
+  for (int a = 0; a < 3; a++) {
+    switch (a) {
+      case 1:
+      case 2:
+        b = 0;
+        ++a;
+        break;
+      default:
+        b = 0;
+    }
+  }
+  print(a+b);
+}
+""";
+
+const String LABEL = """
+void main() {
+  var b;
+  for (int a = 0; a < 3; a++) {
+    switch (a) {
+      case 1:
+        break;
+      case 2:
+        b = 0;
+        continue K;
+      K: case 3:
+        b = 19;
+      default:
+        b = 5;
+    }
+  }
+  print(a+b);
+}
+""";
+
+const String DEFLABEL = """
+void main() {
+  var b;
+  for (int a = 0; a < 3; a++) {
+    switch (a) {
+      case 1:
+        continue L;
+      case 2:
+        b = 0;
+        break;
+      L: default:
+        b = 5;
+    }
+  }
+  print(a+b);
+}
+""";
+
+main() {
+  var def = new RegExp(r"default:");
+  var defOrCase3 = new RegExp(r"(default:|case 3):");
+  var case3 = new RegExp(r"case 3:");
+
+  compileAndDoNotMatch(SIMPLY_EMPTY, 'main', def);
+  compileAndDoNotMatch(TOTAL, 'main', defOrCase3);
+  compileAndDoNotMatch(OPTIMIZED, 'main', def);
+  compileAndMatch(LABEL, 'main', case3);
+  compileAndMatch(DEFLABEL, 'main', def);
+}