Partially decouple NTA proxy objects

Proxy objects are used to locate NTA children from parameterized NTAs
during inherited attribute evaluation. Previously the proxy object was a
list, and the list could be used to iterate over evaluated parameterized
NTA values.

Proxy objects are now plain ASTNode instances, and when not using
rewrites or using circular NTA rewrites they do not contain references
to the child nodes using them as proxy parents.

Null references are no longer stored in the proxy objects in any
configuration.

This change also renames the proxy objects from attrname_list to
attrname_proxy.

see #112 (bitbucket)

ChangeLog

+2016-05-29  Jesper Öqvist <joqvist@google.com>
+
+    * Inherited equations on parameterized NTAs can no longer use the child
+    index which depended on evaluation order.
+    * Made parameterized NTA proxy object more loosely coupled to
+    parameterized NTA values in non-legacy rewrite mode (only setting parent
+    links to proxy object).
+
 2016-03-23  Jesper Öqvist <jesper.oqvist@cs.lth.se>
 
     * Added a new variation of the contributes statement to allow NTA children

src/template/ast/Attributes.tt

@@ -56,7 +56,7 @@ $endif
 $else
 $if(#declaredNTA)
   /** @apilevel internal */
-  protected $List #(signature)_list;
+  protected $ASTNode #(signature)_proxy;
 $endif
 $if(LazyMaps)
   /** @apilevel internal */
@@ -233,12 +233,14 @@ $endif
 
 SynDecl.higherOrderAttributeCode:norewrite [[
 $if(#isParameterized)
-if (#(signature)_list == null) {
-  #(signature)_list = new $List();
+if (#(signature)_proxy == null) {
+  #(signature)_proxy = new $ASTNode();
   $include(AttrDecl.incHookCreateNtaList)
-  #(signature)_list.setParent(this);
+  #(signature)_proxy.setParent(this);
+}
+if (#(signature)_value != null) {
+  #(signature)_value.setParent(#(signature)_proxy);
 }
-#(signature)_list.add(#(signature)_value);
 $else
 #(signature)_value.setParent(this);
 $endif
@@ -246,19 +248,26 @@ $endif
 
 SynDecl.higherOrderAttributeCode:rewritesEnabled [[
 $if(#isParameterized)
-if (#(signature)_list == null) {
-  #(signature)_list = new $List();
+if (#(signature)_proxy == null) {
+  #(signature)_proxy = new $ASTNode();
   $include(AttrDecl.incHookCreateNtaList)
   $if(LegacyRewrite)
-  #(signature)_list.is$$Final = true;
+  #(signature)_proxy.is$$Final = true;
   $endif
-  #(signature)_list.setParent(this);
+  #(signature)_proxy.setParent(this);
 }
-#(signature)_list.add(#(signature)_value);
 if (#(signature)_value != null) {
-  #(signature)_value = (#boxedType) #(signature)_list.getChild(#(signature)_list.numChildren - 1);
   $if(LegacyRewrite)
+  #(signature)_proxy.addChild(#(signature)_value);
+  // Proxy child access is used to trigger rewrite of NTA value.
+  #(signature)_value = (#boxedType) #(signature)_proxy.getChild(#(signature)_proxy.numChildren - 1);
   #(signature)_value.is$$Final = true;
+  $else
+  #(signature)_value.setParent(#(signature)_proxy);
+  if (#(signature)_value.mayHaveRewrite()) {
+    #(signature)_value = (#boxedType) #(signature)_value.rewrittenNode();
+    #(signature)_value.setParent(#(signature)_proxy);
+  }
   $endif
 }
 $else

src/template/ast/Circular.tt

@@ -165,11 +165,11 @@ AttrDecl.circularEquation:parameterized [[
       _value.value = $BottomValue;
 $if(#getNTA)
        if (_value.value != null) {
-         if (#(signature)_list == null) {
-           #(signature)_list = new $List();
-           #(signature)_list.setParent(#ntaParent);
+         if (#(signature)_proxy == null) {
+           #(signature)_proxy = new $ASTNode();
+           #(signature)_proxy.setParent(#ntaParent);
          }
-         (($ASTNode) _value.value).setParent(#(signature)_list);
+         (($ASTNode) _value.value).setParent(#(signature)_proxy);
       }
 $endif
     }
@@ -196,11 +196,11 @@ $endif
           _value.value = new_#(signature)_value;
 $if(#getNTA)
           if (_value.value != null) {
-            if (#(signature)_list == null) {
-              #(signature)_list = new $List();
-              #(signature)_list.setParent(#ntaParent);
+            if (#(signature)_proxy == null) {
+              #(signature)_proxy = new $ASTNode();
+              #(signature)_proxy.setParent(#ntaParent);
             }
-            (($ASTNode) _value.value).setParent(#(signature)_list);
+            (($ASTNode) _value.value).setParent(#(signature)_proxy);
           }
 $endif
         }
@@ -249,11 +249,11 @@ $endif
         _value.value = new_#(signature)_value;
 $if(#getNTA)
         if (_value.value != null) {
-          if (#(signature)_list == null) {
-            #(signature)_list = new $List();
-            #(signature)_list.setParent(#ntaParent);
+          if (#(signature)_proxy == null) {
+            #(signature)_proxy = new $ASTNode();
+            #(signature)_proxy.setParent(#ntaParent);
           }
-          (($ASTNode) _value.value).setParent(#(signature)_list);
+          (($ASTNode) _value.value).setParent(#(signature)_proxy);
         }
 $endif
       }

src/template/ast/InheritedAttributes.tt

@@ -122,7 +122,7 @@ $EvalStmt
 # non-terminal child equation clause
 InhEq.emitNTAClause [[
 $if(IsParameterized)
-if (_callerNode == $(AttrSignature)_list) {
+if (_callerNode == $(AttrSignature)_proxy) {
   // #declaredat
   int $ChildIndexVar = _callerNode.getIndexOfChild(_childNode);
   $EvalStmt

src/template/flush/Flush.tt

@@ -137,7 +137,7 @@ $if(#isLazy)
 #(signature)_values = $CreateDefaultMap;
     $endif
     $if(#getNTA)
-#(signature)_list = null;
+#(signature)_proxy = null;
     $endif
   $else
     $if(#simpleCacheCheck)

src/template/incremental/Debug.tt

@@ -224,8 +224,8 @@ if ($(AttrSign)_handler != null) {
 $endif
 $if (IsNTA)
 $if (IsParameterized)
-if ($(AttrSign)_list != null) {
-  $(AttrSign)_list.dumpDependencies();
+if ($(AttrSign)_proxy != null) {
+  $(AttrSign)_proxy.dumpDependencies();
 }
 $else
 if ($(AttrSign)_computed && ($(AttrSign)_value instanceof $ASTNode)) {
@@ -240,8 +240,8 @@ if ($(AttrSign)_handler != null) {
 }
 $if (IsNTA)
 $if (IsParameterized)
-if ($(AttrSign)_list != null) {
-  $(AttrSign)_list.dumpDependencies();
+if ($(AttrSign)_proxy != null) {
+  $(AttrSign)_proxy.dumpDependencies();
 }
 $else
 if ($(AttrSign)_computed && ($(AttrSign)_value instanceof $ASTNode)) {
@@ -270,8 +270,8 @@ public void #name.dumpDepsInTree() {
 # Generate string with code for dumping dependencies in NTAs
 ASTDecl.checkAndDumpNTADeps = [[
 $if (IsParameterized)
-if ($(AttrSign)_list != null) {
-  $(AttrSign)_list.dumpDepsInTree();
+if ($(AttrSign)_proxy != null) {
+  $(AttrSign)_proxy.dumpDepsInTree();
 }
 $else
 if ($(AttrSign)_computed && ($(AttrSign)_value instanceof $ASTNode)) {

src/template/incremental/NTAs.tt

@@ -63,13 +63,13 @@ $if(IncrementalEnabled)
 
 $if(IncrementalLevelNode)
 $if(#getNTA)
-#(signature)_list.inc_internalNTAList(#(signature)_values);
+#(signature)_proxy.inc_internalNTAList(#(signature)_values);
 $endif
 $endif
 
 $if(IncrementalLevelRegion)
 $if(#getNTA)
-#(signature)_list.inc_internalNTAList(#(signature)_values);
+#(signature)_proxy.inc_internalNTAList(#(signature)_values);
 $endif
 $endif
 

src/template/incremental/Notification.tt

@@ -252,12 +252,12 @@ $if(IsParameterized)
 if (attrID.equals("$AttrSign") && $(AttrSign)_values != null && $(AttrSign)_values.containsKey(_parameters)) {
   $if(IsNTA)
   $AttrType value = ($AttrType)$(AttrSign)_values.remove(_parameters);
-  for (int i = 0; i < $(AttrSign)_list.children.length; i++) {
-    $ASTNode child = $(AttrSign)_list.children[i];
+  for (int i = 0; i < $(AttrSign)_proxy.children.length; i++) {
+    $ASTNode child = $(AttrSign)_proxy.children[i];
     if (child != null && value == child) {
       // using dummy node to flush dependencies from NTA
       value.inc_flush_subtree(($DDGNodeName)$(AttrSign)_handler.get(_parameters));
-      $(AttrSign)_list.removeChild(i);
+      $(AttrSign)_proxy.removeChild(i);
       break;
     }
   }
@@ -296,10 +296,10 @@ $if(IncrementalLevelAttr)
 $if(IsParameterized)
 if (attrID.equals("$AttrSign") && $(AttrSign)_values != null && !$(AttrSign)_values.isEmpty()) {
   $if(IsNTA)
-  if ($(AttrSign)_list != null) {
-    $(AttrSign)_list.setParent(null);
+  if ($(AttrSign)_proxy != null) {
+    $(AttrSign)_proxy.setParent(null);
     // using dummy node to flush dependencies from NTA
-    $(AttrSign)_list.inc_flush_subtree($(AttrSign)_handler);
+    $(AttrSign)_proxy.inc_flush_subtree($(AttrSign)_handler);
   }
   $endif
   $AttrResetVisit
@@ -763,12 +763,12 @@ $if(IncrementalChangeFlush)
 
 $if(IsNTA)
 $if(IsParameterized)
-if ($(AttrSign)_list != null) {
-  for (int index = 0; index < $(AttrSign)_list.numChildren; index++) {
-    $ASTNode value = $(AttrSign)_list.children[index];
+if ($(AttrSign)_proxy != null) {
+  for (int index = 0; index < $(AttrSign)_proxy.numChildren; index++) {
+    $ASTNode value = $(AttrSign)_proxy.children[index];
     if (!value.isRegionRoot()) {
       state().enterConstruction();
-      $(AttrSign)_list.removeChild(index);
+      $(AttrSign)_proxy.removeChild(index);
       // removeChild will decrease the index of all remaining children and numChildren
       // hence, to visit the remainder of the list index need to be decreased by one for each removeChild
       index--;
@@ -998,8 +998,8 @@ $if(IncrementalEnabled)
 $if(IncrementalChangeFlush)
 $if(IsNTA)
 $if(IsParameterized)
-if ($(AttrSign)_list != null) {
-  $(AttrSign)_list.inc_flush_subtree(h);
+if ($(AttrSign)_proxy != null) {
+  $(AttrSign)_proxy.inc_flush_subtree(h);
 }
 $else
 $if(IsNtaWithTree)

src/template/incremental/State.tt

@@ -250,8 +250,8 @@ if ($(AttrSign)_handler != null) {
 $endif
 $if(ChangeStateValue)
 $if(IsParameterized)
-if ($(AttrSign)_list != null) {
-  $(AttrSign)_list.inc_changeState(newState);
+if ($(AttrSign)_proxy != null) {
+  $(AttrSign)_proxy.inc_changeState(newState);
 }
 $else
 if ($(AttrSign)_computed && ($(AttrSign)_value instanceof $ASTNode)) {
@@ -363,8 +363,8 @@ if ($(AttrSign)_handler != null) {
 $endif
 $if(ThrowAwayValue)
 $if(IsParameterized)
-if ($(AttrSign)_list != null) {
-  $(AttrSign)_list.inc_throwAway();
+if ($(AttrSign)_proxy != null) {
+  $(AttrSign)_proxy.inc_throwAway();
 }
 $else
 if ($(AttrSign)_computed && ($(AttrSign)_value instanceof $ASTNode)) {