Handle more BinaryExpression cases

Summary:
Release notes: none

Follow up to https://github.com/facebook/prepack/pull/1464. This adds serializer tests and fixes `+` binary expressions in pure mode.
Closes https://github.com/facebook/prepack/pull/1473

Differential Revision: D7040965

Pulled By: trueadm

fbshipit-source-id: ba2b377b6f7c6fc8260b0afcb5098c6e50c050ed

src/evaluators/BinaryExpression.js

@@ -79,19 +79,30 @@ export function getPureBinaryOperationResultType(
   if (op === "+") {
     let ltype = To.GetToPrimitivePureResultType(realm, lval);
     let rtype = To.GetToPrimitivePureResultType(realm, rval);
+
+    function recoverWithValue() {
+      // Assume that the unknown value is actually a primitive or otherwise a well behaved object.
+      ltype = lval.getType();
+      rtype = rval.getType();
+      if (ltype === StringValue || rtype === StringValue) return StringValue;
+      if (ltype === IntegralValue && rtype === IntegralValue) return IntegralValue;
+      if ((ltype === NumberValue || ltype === IntegralValue) && (rtype === NumberValue || rtype === IntegralValue))
+        return NumberValue;
+
+      return Value;
+    }
+
+    if (realm.isInPureScope()) {
+      if (!ltype) Leak.leakValue(realm, lval);
+      if (!rtype) Leak.leakValue(realm, rval);
+      return recoverWithValue();
+    }
+
     if (ltype === undefined || rtype === undefined) {
       let loc = ltype === undefined ? lloc : rloc;
       let error = new CompilerDiagnostic(unknownValueOfOrToString, loc, "PP0002", "RecoverableError");
       if (realm.handleError(error) === "Recover") {
-        // Assume that the unknown value is actually a primitive or otherwise a well behaved object.
-        ltype = lval.getType();
-        rtype = rval.getType();
-        if (ltype === StringValue || rtype === StringValue) return StringValue;
-        if (ltype === IntegralValue && rtype === IntegralValue) return IntegralValue;
-        if ((ltype === NumberValue || ltype === IntegralValue) && (rtype === NumberValue || rtype === IntegralValue))
-          return NumberValue;
-
-        return Value;
+        return recoverWithValue();
       }
       throw new FatalError();
     }

test/serializer/pure-functions/BinaryExpressions.js

@@ -0,0 +1,19 @@
+// additional functions
+// abstract effects
+
+let obj1 = global.__abstract ? __abstract('object', '({foo: {valueOf() { return 42; }}})') : {foo: {valueOf() { return 42; }}};
+let obj2 = global.__abstract ? __abstract('object', '({foo: {bar: {valueOf() { return 42; }}}})') : {foo: {bar: {valueOf() { return 42; }}}};
+
+function additional1() {
+  return '' + obj1.foo;
+}
+
+function additional2() {
+  return obj2.foo.bar + 10;
+}
+
+inspect = function() {
+  let ret1 = additional1();
+  let ret2 = additional2();
+  return JSON.stringify({ ret1, ret2 });
+}

test/serializer/pure-functions/BinaryExpressions2.js

@@ -0,0 +1,19 @@
+// additional functions
+// abstract effects
+
+let obj1 = global.__abstract ? __abstract('object', '({foo: {valueOf() { return 42; }}})') : {foo: {valueOf() { return 42; }}};
+let obj2 = global.__abstract ? __abstract('object', '({foo: {bar: {valueOf() { return 42; }}}})') : {foo: {bar: {valueOf() { return 42; }}}};
+
+function additional1() {
+  return 42 < obj1.foo;
+}
+
+function additional2() {
+  return obj2.foo.bar > 42;
+}
+
+inspect = function() {
+  let ret1 = additional1();
+  let ret2 = additional2();
+  return JSON.stringify({ ret1, ret2 });
+}