Fix a bug in IRGen when dealing with mixed literal and computed props

Summary:
In IRGen when generating IR for object initialization, we always generate StoreNewOwnPropertyInst for every literal property. This is to assume that every property must always be new. However with the introduction of computed property, this is no longer true, as a computed property could in theory define any property.
To fix this, whenever we encounter a computed property, we can no longer generate StoreNewOwnPropertyInst in the future, but always generate StoreOwnPropertyInst instead.

Reviewed By: avp

Differential Revision: D16231160

fbshipit-source-id: 581dbae96d0e0d38ce53278c0d97aaec9f916966

lib/IRGen/ESTreeIRGen-expr.cpp

@@ -468,6 +468,12 @@ Value *ESTreeIRGen::genObjectExpr(ESTree::ObjectExpressionNode *Expr) {
   auto Obj =
       Builder.createAllocObjectInst(propMap.size() + numComputed, objectParent);
 
+  // haveSeenComputedProp tracks whether we have processed a computed property.
+  // Once we do, for all future properties, we can no longer generate
+  // StoreNewOwnPropertyInst because the computed property could have already
+  // defined any property.
+  bool haveSeenComputedProp = false;
+
   // Initialize all properties. We check whether the value of each property
   // will be overwritten (by comparing against what we have saved in propMap).
   // In that case we still compute the value (it could have side effects), but
@@ -514,6 +520,7 @@ Value *ESTreeIRGen::genObjectExpr(ESTree::ObjectExpressionNode *Expr) {
         Builder.createStoreOwnPropertyInst(
             value, Obj, key, IRBuilder::PropEnumerable::Yes);
       }
+      haveSeenComputedProp = true;
       continue;
     }
 
@@ -585,8 +592,13 @@ Value *ESTreeIRGen::genObjectExpr(ESTree::ObjectExpressionNode *Expr) {
 
       // Only store the value if it won't be overwritten.
       if (propMap[keyStr].valueNode == prop->_value) {
-        Builder.createStoreNewOwnPropertyInst(
-            value, Obj, Key, IRBuilder::PropEnumerable::Yes);
+        if (haveSeenComputedProp) {
+          Builder.createStoreOwnPropertyInst(
+              value, Obj, Key, IRBuilder::PropEnumerable::Yes);
+        } else {
+          Builder.createStoreNewOwnPropertyInst(
+              value, Obj, Key, IRBuilder::PropEnumerable::Yes);
+        }
       } else {
         Builder.getModule()->getContext().getSourceErrorManager().warning(
             propMap[keyStr].getSourceRange(),

test/hermes/es6/computed-props.js

@@ -55,3 +55,18 @@ print(getset['x']);
 // CHECK-NEXT: 13
 getset['x'] = 101;
 // CHECK-NEXT: set 101
+
+var mixed_props = {
+  ['b']: 'b',
+  b: 'B',
+};
+
+print(Object.keys(mixed_props));
+// CHECK-NEXT: b
+
+var getters = {
+  get ['x']() {},
+  x: 3,
+};
+print(getters.x);
+// CHECK-NEXT: 3