Fix for type analysis bug in constructor with early return

tests/compiler/dart2js/field_type_simple_inferer_test.dart

Index: tests/compiler/dart2js/field_type_simple_inferer_test.dart
diff --git a/tests/compiler/dart2js/field_type_simple_inferer_test.dart b/tests/compiler/dart2js/field_type_simple_inferer_test.dart
index 2d64709223787e86e1f04ed3b55dae3c4a90aa86..2eaf8085a537a9c24e5e39bc820136d0747bcde9 100644
--- a/tests/compiler/dart2js/field_type_simple_inferer_test.dart
+++ b/tests/compiler/dart2js/field_type_simple_inferer_test.dart
@@ -470,6 +470,63 @@ const String TEST_27 = r"""
   }
 """;
 
+const String TEST_28 = r"""
+  class A {
+    var f1;
+    var f2;
+    A(x) {
+      this.f1 = x;
+      if (x == 0) return;
+      this.f2 = x;
+    }
+  }
+  main() {
+    new A(0);
+    new A(1);
+  }
+""";
+
+const String TEST_29 = r"""
+  class A {
+    var f1;
+    var f2;
+    A(x) {
+      this.f1 = x;
+      if (x == 0) {
+      } else {
+        return;
+      }
+      this.f2 = x;
+    }
+  }
+  main() {
+    new A(0);
+    new A(1);
+  }
+""";
+
+const String TEST_30 = r"""
+  class A {
+    var f1;
+    var f2;
+    var f3;
+    A(x) {
+      this.f1 = x;
+      if (x == 0) {
+        this.f2 = 1;
+      } else {
+        this.f2 = x;
+        return;
+      }
+      this.f3 = x;
+    }
+  }
+  main() {
+    new A(0);
+    new A(1);
+  }
+""";
+
 typedef TypeMask TestCallback(ClosedWorld closedWorld);
 
 void doTest(
@@ -481,7 +538,7 @@ void doTest(
       TypeMask type = f(closedWorld);
       TypeMask inferredType =
           simplify(inferrer.getTypeOfElement(field), closedWorld);
-      Expect.equals(type, inferredType, test);
+      Expect.equals(type, inferredType, '$name of:\n$test');
     });
   });
 }
@@ -609,6 +666,19 @@ void test() {
     'f1': (closedWorld) => closedWorld.commonMasks.uint31Type,
     'f2': (closedWorld) => closedWorld.commonMasks.uint31Type.nullable()
   });
+  runTest(TEST_28, <String, TestCallback>{
+    'f1': (closedWorld) => closedWorld.commonMasks.uint31Type,
+    'f2': (closedWorld) => closedWorld.commonMasks.uint31Type.nullable()
+  });
+  runTest(TEST_29, <String, TestCallback>{
+    'f1': (closedWorld) => closedWorld.commonMasks.uint31Type,
+    'f2': (closedWorld) => closedWorld.commonMasks.uint31Type.nullable()
+  });
+  runTest(TEST_30, <String, TestCallback>{
+    'f1': (closedWorld) => closedWorld.commonMasks.uint31Type,
+    'f2': (closedWorld) => closedWorld.commonMasks.uint31Type,
+    'f3': (closedWorld) => closedWorld.commonMasks.uint31Type.nullable()
+  });
 }
 
 void main() {