From 2b600a3d569b2d519a5e057783976b0e055a7761 Mon Sep 17 00:00:00 2001
From: Chris Blappert <blappert@fb.com>
Date: Thu, 1 Mar 2018 15:47:59 -0800
Subject: [PATCH] Fix additional functions refactor

Summary:
Fix for bug NTillmann encountered with the additional functions refactor.

Every function references itself through its `arguments`, so additional functions were recursively trying to visit themselves while visiting their arguments. It doesn't make sense to visit a function from its own scope, so we add a check to the visitor preventing this.
Closes https://github.com/facebook/prepack/pull/1508

Differential Revision: D7130078

Pulled By: cblappert

fbshipit-source-id: ecb0497456169f3ff41c89f2fcf17e3ae9670d96
---
 src/serializer/ResidualHeapVisitor.js             | 10 ++++++----
 .../additional-functions/self_referential.js      | 15 +++++++++++++++
 2 files changed, 21 insertions(+), 4 deletions(-)
 create mode 100644 test/serializer/additional-functions/self_referential.js

diff --git a/src/serializer/ResidualHeapVisitor.js b/src/serializer/ResidualHeapVisitor.js
index bdcb9aaa5..1488a9443 100644
--- a/src/serializer/ResidualHeapVisitor.js
+++ b/src/serializer/ResidualHeapVisitor.js
@@ -786,10 +786,12 @@ export class ResidualHeapVisitor {
     } else if (val instanceof FunctionValue) {
       // Function declarations should get hoisted in common scope so that instances only get allocated once
       let parentScope = this.scope;
-      this._withScope(this.commonScope, () => {
-        invariant(val instanceof FunctionValue);
-        if (this.preProcessValue(val)) this.visitValueFunction(val, parentScope);
-      });
+      // Every function references itself through arguments, prevent the recursive double-visit
+      if (this.scope !== val && this.commonScope !== val)
+        this._withScope(this.commonScope, () => {
+          invariant(val instanceof FunctionValue);
+          if (this.preProcessValue(val)) this.visitValueFunction(val, parentScope);
+        });
     } else if (val instanceof SymbolValue) {
       if (this.preProcessValue(val)) this.visitValueSymbol(val);
     } else {
diff --git a/test/serializer/additional-functions/self_referential.js b/test/serializer/additional-functions/self_referential.js
new file mode 100644
index 000000000..80f3fe1e5
--- /dev/null
+++ b/test/serializer/additional-functions/self_referential.js
@@ -0,0 +1,15 @@
+// does not contain:x = 5;
+
+function func1() {
+  let x = 5;
+  let z = [ func1 ];
+  return z;
+}
+
+if (global.__registerAdditionalFunctionToPrepack) {
+  __registerAdditionalFunctionToPrepack(func1);
+}
+
+inspect = function() {
+  return func1()[0] === func1()[0];
+}