Reimplement Maps and Sets in JS

src/runtime.js

Index: src/runtime.js
diff --git a/src/runtime.js b/src/runtime.js
index 7d82dfa8463fac3305ca98f42dd9a5545444a40c..bc1e47686c8813a705ba812cb8ba283294eb1504 100644
--- a/src/runtime.js
+++ b/src/runtime.js
@@ -613,12 +613,10 @@ function SameValue(x, y) {
 
 // ES6, section 7.2.4
 function SameValueZero(x, y) {
-  if (typeof x != typeof y) return false;
-  if (IS_NUMBER(x)) {
-    if (NUMBER_IS_NAN(x) && NUMBER_IS_NAN(y)) return true;
-  }
-  return x === y;
+  if (x === y) return true;
+  return IS_NUMBER(x) && NUMBER_IS_NAN(x) && IS_NUMBER(y) && NUMBER_IS_NAN(y);
 }
+%SetInlineBuiltinFlag(SameValueZero);
 
 
 /* ---------------------------------