[MERGE chakra-core#3610 @pleath] [MSFT 13209141]: Defer default expressions in a formals list if the function containing them is going to be deferred.

pleath · pleath · commit 50ce23ee9dfd · 2017-08-29T16:39:18.000-07:00
Merge pull request chakra-core#3610 from pleath:13209141 We know that the expressions can't be evaluated until the function has been fully compiled, so compiling the expressions up front is wasted work. And generating code for a function nested inside a deferred function creates inconsistencies.
diff --git a/lib/Parser/Parse.cpp b/lib/Parser/Parse.cpp
@@ -5195,7 +5195,7 @@ bool Parser::ParseFncDeclHelper(ParseNodePtr pnodeFnc, LPCOLESTR pNameHint, usho
                 saveDeferredStub = m_currDeferredStub;
                 m_currDeferredStub = nullptr;
             }
-            this->ParseFncFormals<buildAST>(pnodeFnc, pnodeFncParent, flags);
+            this->ParseFncFormals<buildAST>(pnodeFnc, pnodeFncParent, flags, isTopLevelDeferredFunc);
             if (buildAST)
             {
                 m_currDeferredStub = saveDeferredStub;
@@ -6227,7 +6227,7 @@ void Parser::UpdateOrCheckForDuplicateInFormals(IdentPtr pid, SList<IdentPtr> *f
 }
 
 template<bool buildAST>
-void Parser::ParseFncFormals(ParseNodePtr pnodeFnc, ParseNodePtr pnodeParentFnc, ushort flags)
+void Parser::ParseFncFormals(ParseNodePtr pnodeFnc, ParseNodePtr pnodeParentFnc, ushort flags, bool isTopLevelDeferredFunc)
 {
     bool fLambda = (flags & fFncLambda) != 0;
     bool fMethod = (flags & fFncMethod) != 0;
@@ -6439,9 +6439,21 @@ void Parser::ParseFncFormals(ParseNodePtr pnodeFnc, ParseNodePtr pnodeParentFnc,
                     }
 
                     m_pscan->Scan();
-                    ParseNodePtr pnodeInit = ParseExpr<buildAST>(koplCma, nullptr, TRUE, FALSE, pNameHint, &nameHintLength, &nameHintOffset);
 
-                    if (buildAST && pnodeInit->nop == knopFncDecl)
+                    ParseNodePtr pnodeInit;
+                    if (isTopLevelDeferredFunc)
+                    {
+                        // Defer default expressions if the function will be deferred, since we know they can't be evaluated
+                        // until the function is fully compiled, and generating code for a function nested inside a deferred function
+                        // creates inconsistencies.
+                        pnodeInit = ParseExpr<false>(koplCma, nullptr, TRUE, FALSE, pNameHint, &nameHintLength, &nameHintOffset);
+                    }
+                    else
+                    {
+                        pnodeInit = ParseExpr<buildAST>(koplCma, nullptr, TRUE, FALSE, pNameHint, &nameHintLength, &nameHintOffset);
+                    }
+
+                    if (buildAST && pnodeInit && pnodeInit->nop == knopFncDecl)
                     {
                         Assert(nameHintLength >= nameHintOffset);
                         pnodeInit->sxFnc.hint = pNameHint;
diff --git a/lib/Parser/Parse.h b/lib/Parser/Parse.h
@@ -773,7 +773,7 @@ class Parser
     template<bool buildAST> ParseNodePtr ParseMemberGetSet(OpCode nop, LPCOLESTR* ppNameHint);
     template<bool buildAST> ParseNodePtr ParseFncDecl(ushort flags, LPCOLESTR pNameHint = NULL, const bool needsPIDOnRCurlyScan = false, bool resetParsingSuperRestrictionState = true, bool fUnaryOrParen = false);
     template<bool buildAST> bool ParseFncNames(ParseNodePtr pnodeFnc, ParseNodePtr pnodeFncParent, ushort flags, ParseNodePtr **pLastNodeRef);
-    template<bool buildAST> void ParseFncFormals(ParseNodePtr pnodeFnc, ParseNodePtr pnodeParentFnc, ushort flags);
+    template<bool buildAST> void ParseFncFormals(ParseNodePtr pnodeFnc, ParseNodePtr pnodeParentFnc, ushort flags, bool isTopLevelDeferredFunc = false);
     template<bool buildAST> bool ParseFncDeclHelper(ParseNodePtr pnodeFnc, LPCOLESTR pNameHint, ushort flags, bool *pHasName, bool fUnaryOrParen, bool noStmtContext, bool *pNeedScanRCurly, bool skipFormals = false);
     template<bool buildAST> void ParseExpressionLambdaBody(ParseNodePtr pnodeFnc);
     template<bool buildAST> void UpdateCurrentNodeFunc(ParseNodePtr pnodeFnc, bool fLambda);
diff --git a/test/es6/classes_bugfixes.js b/test/es6/classes_bugfixes.js
@@ -464,6 +464,16 @@ var tests = [
         assert.areEqual('Bsetter;Bgetter;', result);
     }
   },
+  {
+    name: "MSFT:13209141: Confusion on deferred function containing non-deferred extends cause calling eval",
+    body: function () {
+      function foo(a = class c extends eval("") {}) {}
+      try {
+        foo();
+      }
+      catch(e) {}
+    }
+  },
 ];
 
 testRunner.runTests(tests, { verbose: WScript.Arguments[0] != "summary" });
