Genex: Simplify TARGET_PROPERTY transitive lookup

In cmGeneratorExpressionEvaluator, make getLinkedTargetsContent a
template so it can traverse over either the Libraries in a cmTarget
LinkImplementationLibraries or a cmTarget LinkInterfaceLibraries.  This
also avoids creating a separate vector<cmTarget*>.

Source/cmGeneratorExpressionEvaluator.cxx

@@ -799,70 +799,49 @@ static const char* targetPropertyTransitiveWhitelist[] = {
 
 #undef TRANSITIVE_PROPERTY_NAME
 
+template <typename T>
 std::string
 getLinkedTargetsContent(
-  std::vector<cmTarget const*> &targets,
+  std::vector<T> const &libraries,
   cmTarget const* target,
   cmTarget const* headTarget,
   cmGeneratorExpressionContext *context,
   cmGeneratorExpressionDAGChecker *dagChecker,
   const std::string &interfacePropertyName)
 {
-  cmGeneratorExpression ge(&context->Backtrace);
-
+  std::string linkedTargetsContent;
   std::string sep;
   std::string depString;
-  for (std::vector<cmTarget const*>::const_iterator
-      it = targets.begin();
-      it != targets.end(); ++it)
+  for (typename std::vector<T>::const_iterator it = libraries.begin();
+       it != libraries.end(); ++it)
     {
-    if (*it == target)
-      {
-      // Broken code can have a target in its own link interface.
-      // Don't follow such link interface entries so as not to create a
-      // self-referencing loop.
-      continue;
+    // Broken code can have a target in its own link interface.
+    // Don't follow such link interface entries so as not to create a
+    // self-referencing loop.
+    if (it->Target && it->Target != target)
+      {
+      depString +=
+        sep + "$<TARGET_PROPERTY:" +
+        it->Target->GetName() + "," + interfacePropertyName + ">";
+      sep = ";";
       }
-    depString +=
-      sep + "$<TARGET_PROPERTY:" +
-        (*it)->GetName() + "," + interfacePropertyName + ">";
-    sep = ";";
     }
-  cmsys::auto_ptr<cmCompiledGeneratorExpression> cge = ge.Parse(depString);
-  std::string linkedTargetsContent = cge->Evaluate(target->GetMakefile(),
-                      context->Config,
-                      context->Quiet,
-                      headTarget,
-                      target,
-                      dagChecker);
-  if (cge->GetHadContextSensitiveCondition())
-    {
-    context->HadContextSensitiveCondition = true;
-    }
-  return linkedTargetsContent;
-}
-
-std::string
-getLinkedTargetsContent(
-  std::vector<cmLinkImplItem> const &libraries,
-  cmTarget const* target,
-  cmTarget const* headTarget,
-  cmGeneratorExpressionContext *context,
-  cmGeneratorExpressionDAGChecker *dagChecker,
-  const std::string &interfacePropertyName)
-{
-  std::vector<cmTarget const*> tgts;
-  for (std::vector<cmLinkImplItem>::const_iterator
-      it = libraries.begin();
-      it != libraries.end(); ++it)
+  if(!depString.empty())
     {
-    if (it->Target)
-      {
-      tgts.push_back(it->Target);
+    cmGeneratorExpression ge(&context->Backtrace);
+    cmsys::auto_ptr<cmCompiledGeneratorExpression> cge = ge.Parse(depString);
+    linkedTargetsContent = cge->Evaluate(target->GetMakefile(),
+                                         context->Config,
+                                         context->Quiet,
+                                         headTarget,
+                                         target,
+                                         dagChecker);
+    if (cge->GetHadContextSensitiveCondition())
+      {
+      context->HadContextSensitiveCondition = true;
       }
     }
-  return getLinkedTargetsContent(tgts, target, headTarget, context,
-                                 dagChecker, interfacePropertyName);
+  return linkedTargetsContent;
 }
 
 //----------------------------------------------------------------------------
@@ -1098,27 +1077,14 @@ static const struct TargetPropertyNode : public cmGeneratorExpressionNode
     if (std::find_if(transBegin, transEnd,
                      cmStrCmp(propertyName)) != transEnd)
       {
-      std::vector<cmTarget const*> tgts;
       if(cmTarget::LinkInterfaceLibraries const* iface =
          target->GetLinkInterfaceLibraries(context->Config, headTarget, true))
         {
-        for(std::vector<cmLinkItem>::const_iterator
-              it = iface->Libraries.begin();
-            it != iface->Libraries.end(); ++it)
-          {
-          if (it->Target)
-            {
-            tgts.push_back(it->Target);
-            }
-          }
-        }
-      if (!tgts.empty())
-        {
         linkedTargetsContent =
-                  getLinkedTargetsContent(tgts, target,
-                                          headTarget,
-                                          context, &dagChecker,
-                                          interfacePropertyName);
+          getLinkedTargetsContent(iface->Libraries, target,
+                                  headTarget,
+                                  context, &dagChecker,
+                                  interfacePropertyName);
         }
       }
     else if (std::find_if(transBegin, transEnd,