Identify direct children of yield expressions

We want to be able to recognize them without knowing their
context.

hphp/compiler/analysis/alias_manager.cpp

@@ -36,6 +36,7 @@
 #include "hphp/compiler/expression/expression.h"
 #include "hphp/compiler/expression/include_expression.h"
 #include "hphp/compiler/expression/closure_expression.h"
+#include "hphp/compiler/expression/yield_expression.h"
 #include "hphp/compiler/statement/statement.h"
 #include "hphp/compiler/statement/statement_list.h"
 #include "hphp/compiler/statement/catch_statement.h"
@@ -2115,6 +2116,7 @@ int AliasManager::collectAliasInfoRecur(ConstructPtr cs, bool unused) {
   }
 
   cs->clearVisited();
+  cs->clearChildOfYield();
 
   StatementPtr s = dpc(Statement, cs);
   if (s) {
@@ -2405,6 +2407,9 @@ int AliasManager::collectAliasInfoRecur(ConstructPtr cs, bool unused) {
         // expressions. TODO: revisit this later
         m_inlineAsExpr = false;
         break;
+      case Expression::KindOfYieldExpression:
+        spc(YieldExpression, e)->getValueExpression()->setChildOfYield();
+        break;
       case Expression::KindOfUnaryOpExpression:
         if (Option::EnableEval > Option::NoEval && spc(UnaryOpExpression, e)->
             getOp() == T_EVAL) {

hphp/compiler/construct.h

@@ -166,6 +166,10 @@ public:
   void clearKilled() { m_flags.killed = false; }
   bool isKilled() const { return m_flags.killed; }
 
+  void setChildOfYield() { m_flags.childOfYield = true; }
+  void clearChildOfYield() { m_flags.childOfYield = false; }
+  bool isChildOfYield() const { return m_flags.childOfYield; }
+
   BlockScopeRawPtr getScope() const { return m_blockScope; }
   void setBlockScope(BlockScopeRawPtr scope) { m_blockScope = scope; }
   FileScopeRawPtr getFileScope() const {
@@ -295,6 +299,7 @@ private:
       unsigned killed              : 1;
       unsigned refCounted          : 2; // high bit indicates whether its valid
       unsigned inited              : 2; // high bit indicates whether its valid
+      unsigned childOfYield        : 1; // parent node is yield
     } m_flags;
   };
 protected:

hphp/compiler/expression/expression.cpp

@@ -70,6 +70,7 @@ ExpressionPtr Expression::replaceValue(ExpressionPtr rep) {
     rep->clearContext(AssignmentRHS);
     rep = el;
   }
+  if (isChildOfYield()) rep->setChildOfYield();
   if (rep->is(KindOfSimpleVariable) && !is(KindOfSimpleVariable)) {
     static_pointer_cast<SimpleVariable>(rep)->setAlwaysStash();
   }

hphp/compiler/expression/yield_expression.cpp

@@ -50,6 +50,7 @@ void YieldExpression::analyzeProgram(AnalysisResultPtr ar) {
   if (m_keyExp) {
     m_keyExp->analyzeProgram(ar);
   }
+  m_valExp->setChildOfYield();
   m_valExp->analyzeProgram(ar);
   if (m_label == -1) {
     setLabel(getFunctionScope()->allocYieldLabel());

hphp/test/slow/compilation/invalid_result.php

@@ -0,0 +1,5 @@
+<?php
+
+function test() {
+  list($a, $b) = yield wait_forva(result(1), result(2));
+}