Implements #1674 "augment TerminalNode with setParent()" for Swift target.

runtime/Swift/Sources/Antlr4/Parser.swift

@@ -595,35 +595,21 @@ open class Parser: Recognizer<ParserATNSimulator> {
     }
     
     /** How to create a token leaf node associated with a parent.
-     *  Typically, the terminal node to create is not a function of the parent
-     *  but this method must still set the parent pointer of the terminal node
-     *  returned. I would prefer having {@link ParserRuleContext#addAnyChild(ParseTree)}
-     *  set the parent pointer, but the parent pointer is implementation dependent
-     *  and currently there is no setParent() in {@link TerminalNode} (and can't
-     *  add method in Java 1.7 without breaking backward compatibility).
+     *  Typically, the terminal node to create is not a function of the parent.
      *
      *  @since 4.6.1
      */
     public func createTerminalNode(parent: ParserRuleContext, t: Token) -> TerminalNode {
-     	let node = TerminalNodeImpl(t);
-     	node.parent = parent;
-     	return node;
+     	return TerminalNodeImpl(t);
     }
     
     /** How to create an error node, given a token, associated with a parent.
-     *  Typically, the error node to create is not a function of the parent
-     *  but this method must still set the parent pointer of the terminal node
-     *  returned. I would prefer having {@link ParserRuleContext#addAnyChild(ParseTree)}
-     *  set the parent pointer, but the parent pointer is implementation dependent
-     *  and currently there is no setParent() in {@link ErrorNode} (and can't
-     *  add method in Java 1.7 without breaking backward compatibility).
+     *  Typically, the error node to create is not a function of the parent.
      *
      *  @since 4.6.1
      */
     public func createErrorNode(parent: ParserRuleContext, t: Token) -> ErrorNode {
-    	let node = ErrorNode(t);
-    	node.parent = parent;
-    	return node;
+    	return ErrorNode(t);
     }
 
     internal func addContextToParseTree() {

runtime/Swift/Sources/Antlr4/ParserRuleContext.swift

@@ -72,6 +72,14 @@ open class ParserRuleContext: RuleContext {
 
     /** COPY a ctx (I'm deliberately not using copy constructor) to avoid
      *  confusion with creating node with parent. Does not copy children.
+     *
+     *  This is used in the generated parser code to flip a generic XContext
+     *  node for rule X to a YContext for alt label Y. In that sense, it is
+     *  not really a generic copy function.
+     *
+     *  If we do an error sync() at start of a rule, we might add error nodes
+     *  to the generic XContext so this function must copy those nodes to
+     *  the YContext as well else they are lost!
      */
     open func copyFrom(_ ctx: ParserRuleContext) {
         self.parent = ctx.parent
@@ -81,13 +89,12 @@ open class ParserRuleContext: RuleContext {
         self.stop = ctx.stop
         
         // copy any error nodes to alt label node
-        if  ctx.children != nil{
+        if  ctx.children != nil {
             self.children = Array<ParseTree>()
             // reset parent pointer for any error nodes
-            for  child: ParseTree in ctx.children!  {
-                if  child is ErrorNode{
-                    self.children?.append(child)
-                    ( (child as! ErrorNode)).parent = self
+            for  child: ParseTree in ctx.children! {
+                if  child is ErrorNode {
+                    addChild(child as! ErrorNode)
                 }
             }
         }
@@ -130,14 +137,20 @@ open class ParserRuleContext: RuleContext {
         return addAnyChild(ruleInvocation)
     }
     
+    /** Add a token leaf node child and force its parent to be this node. */
     @discardableResult
     open func addChild(_ t: TerminalNode) -> TerminalNode {
+        t.setParent(self)
         return addAnyChild(t)
     }
     
-    /** Add an error node child. @since 4.6.1 */
+    /** Add an error node child and force its parent to be this node.
+     *
+     *  @since 4.6.1 
+     */
     @discardableResult
     open func addErrorNode(_ errorNode: ErrorNode) -> ErrorNode {
+        errorNode.setParent(self)
         return addAnyChild(errorNode)
     }
 
@@ -150,7 +163,7 @@ open class ParserRuleContext: RuleContext {
     open func addChild(_ matchedToken: Token) -> TerminalNode {
         let t: TerminalNodeImpl = TerminalNodeImpl(matchedToken)
         addAnyChild(t)
-        t.parent = self
+        t.setParent(self)
         return t
     }
     
@@ -164,7 +177,7 @@ open class ParserRuleContext: RuleContext {
     open func addErrorNode(_ badToken: Token) -> ErrorNode {
         let t: ErrorNode = ErrorNode(badToken)
         addAnyChild(t)
-        t.parent = self
+        t.setParent(self)
         return t
     }
     

runtime/Swift/Sources/Antlr4/tree/TerminalNode.swift

@@ -9,4 +9,18 @@ public class TerminalNode: ParseTree {
         fatalError()
 
     }
+    
+    /** Set the parent for this leaf node.
+     *
+     *  Technically, this is not backward compatible as it changes
+     *  the interface but no one was able to create custom
+     *  TerminalNodes anyway so I'm adding as it improves internal
+     *  code quality.
+     *
+     *  @since 4.6.1
+     */
+    public func setParent(_ parent: RuleContext) {
+        RuntimeException(" must overriden !")
+        fatalError()
+    }
 }

runtime/Swift/Sources/Antlr4/tree/TerminalNodeImpl.swift

@@ -27,6 +27,11 @@ public class TerminalNodeImpl: TerminalNode {
         return parent
     }
 
+    override
+    public func setParent(_ parent: RuleContext) {
+        self.parent = parent
+    }
+
     override
     public func getPayload() -> AnyObject {
         return symbol