Optimize DateTime properties

pkg/compiler/lib/src/inferrer/type_graph_nodes.dart

Index: pkg/compiler/lib/src/inferrer/type_graph_nodes.dart
diff --git a/pkg/compiler/lib/src/inferrer/type_graph_nodes.dart b/pkg/compiler/lib/src/inferrer/type_graph_nodes.dart
index dac18f95c18ebd24cebef6be65468743df024a75..1edf437d85cbb3822f238f6a7fe44225d40eef2c 100644
--- a/pkg/compiler/lib/src/inferrer/type_graph_nodes.dart
+++ b/pkg/compiler/lib/src/inferrer/type_graph_nodes.dart
@@ -804,11 +804,17 @@ class DynamicCallSiteTypeInformation extends CallSiteTypeInformation {
     // Dart code, for example:
     // int + int -> int
     // uint31 | uint31 -> uint31
-    if (name == '*' || name == '+' || name == '%' || name == 'remainder' ||
+    if (name == '*' || name == '+' ||name == '%' || name == 'remainder' ||
         name == '~/') {
       if (isPositiveInt(receiver) &&
           arguments.hasOnePositionalArgumentThatMatches(isPositiveInt)) {
-        return inferrer.types.positiveIntType;
+        // uint31 + uint31 -> uint32
+        if (name == '+' && isUInt31(receiver) &&
+            arguments.hasOnePositionalArgumentThatMatches(isUInt31)) {
+          return inferrer.types.uint32Type;
+        } else {
+          return inferrer.types.positiveIntType;
+        }
       } else if (arguments.hasOnePositionalArgumentThatMatches(isInt)) {
         return inferrer.types.intType;
       } else if (arguments.hasOnePositionalArgumentThatMatches(isEmpty)) {