Only emit typeguards if we think they are valuable.

frog/tests/leg/src/TypeGuardUnuserTest.dart

Index: frog/tests/leg/src/TypeGuardUnuserTest.dart
diff --git a/frog/tests/leg/src/TypeGuardUnuserTest.dart b/frog/tests/leg/src/TypeGuardUnuserTest.dart
index 188685c3d0bff499de3fc396d8e7fb3233e09887..80864cf74bbdb42a85ff96612406020f936f53b1 100644
--- a/frog/tests/leg/src/TypeGuardUnuserTest.dart
+++ b/frog/tests/leg/src/TypeGuardUnuserTest.dart
@@ -29,6 +29,15 @@ foo(int param1, int param2) {
 }
 """;
 
+final String TEST_THREE_WITH_BAILOUT = @"""
+foo(int param1, int param2) {
+  var t;
+  for (int i = 0; i < 1; i++) {
+    t = 0 + param1 + param2;
+  }
+  return t;
+}
+""";
 
 main() {
   String generated = compile(TEST_ONE, 'foo');
@@ -46,6 +55,12 @@ main() {
 
   generated = compile(TEST_THREE, 'foo');
   regexp = new RegExp(getNumberTypeCheck('param1'));
+  Expect.isTrue(!regexp.hasMatch(generated));
+  regexp = new RegExp(getNumberTypeCheck('param2'));
+  Expect.isTrue(!regexp.hasMatch(generated));
+
+  generated = compile(TEST_THREE_WITH_BAILOUT, 'foo');
+  regexp = new RegExp(getNumberTypeCheck('param1'));
   Expect.isTrue(regexp.hasMatch(generated));
   regexp = new RegExp(getNumberTypeCheck('param2'));
   Expect.isTrue(regexp.hasMatch(generated));