stash; got lost of visitor stuff working

runtime/Java/src/org/antlr/v4/runtime/ParserRuleContext.java

@@ -34,6 +34,7 @@ import org.antlr.v4.runtime.misc.NotNull;
 import org.antlr.v4.runtime.misc.Nullable;
 import org.antlr.v4.runtime.tree.ParseTree;
 import org.antlr.v4.runtime.tree.ParseTreeListener;
+import org.antlr.v4.runtime.tree.ParseTreeVisitor;
 
 import java.util.ArrayList;
 import java.util.Collections;
@@ -131,10 +132,11 @@ public class ParserRuleContext<Symbol> extends RuleContext {
 		this(parent, parent!=null ? parent.s : -1 /* invoking state */, stateNumber);
 	}
 
-	// Double dispatch methods
+	// Double dispatch methods for listeners and visitors
 
 	public void enterRule(ParseTreeListener<Symbol> listener) { }
 	public void exitRule(ParseTreeListener<Symbol> listener) { }
+	public <T,V extends ParseTreeVisitor<T>> T dispatch(V visitor) { visitor.visitChildren(this); return null; }
 
 	/** Does not set parent link; other add methods do */
 	public void addChild(TerminalNode<Symbol> t) {

runtime/Java/src/org/antlr/v4/runtime/tree/ParseTreeVisitor.java

@@ -0,0 +1,27 @@
+package org.antlr.v4.runtime.tree;
+
+import org.antlr.v4.runtime.ParserRuleContext;
+import org.antlr.v4.runtime.Token;
+
+/** T is return type of visit methods. Use T=Void for no return type. */
+public class ParseTreeVisitor<T> {
+	public T visit(ParserRuleContext<?> ctx) {
+		return ctx.dispatch(this);
+	}
+
+	/** Visit all rule, nonleaf children */
+	public <Symbol> void visitChildren(ParserRuleContext<Symbol> ctx) {
+		for (ParseTree c : ctx.children) {
+			if ( c instanceof ParseTree.RuleNode) {
+				ParseTree.RuleNode r = (ParseTree.RuleNode)c;
+				ParserRuleContext<Symbol> rctx = (ParserRuleContext<Symbol>)r.getRuleContext();
+				rctx.dispatch(this);
+			}
+		}
+	}
+
+//  Don't need to visit tokens. each visit() method deals with it's leaf children
+//	public T visit(Token t) {
+//		return null;
+//	}
+}

tool/playground/ABaseVisitor.java

@@ -0,0 +1,11 @@
+import org.antlr.v4.runtime.Token;
+import org.antlr.v4.runtime.tree.ParseTreeVisitor;
+
+public class ABaseVisitor<T> extends ParseTreeVisitor<T> implements AVisitor<T> {
+	public T visit(AParser.MultContext ctx) { return null; }
+	public T visit(AParser.ParensContext ctx) { return null; }
+	public T visit(AParser.eContext ctx) { return null; }
+	public T visit(AParser.sContext ctx) { return null; }
+	public T visit(AParser.AddContext ctx) { return null; }
+	public T visit(AParser.IntContext ctx) { return null; }
+}

tool/playground/AVisitor.java

@@ -0,0 +1,11 @@
+import org.antlr.v4.runtime.ParserRuleContext;
+import org.antlr.v4.runtime.Token;
+
+public interface AVisitor<T> {
+	T visit(AParser.MultContext ctx);
+	T visit(AParser.ParensContext ctx);
+	T visit(AParser.sContext ctx);
+	T visit(AParser.AddContext ctx);
+	T visit(AParser.IntContext ctx);
+//	T visit(Token t);
+}

tool/playground/TestVisitor.java

@@ -0,0 +1,79 @@
+/*
+ [The "BSD license"]
+ Copyright (c) 2011 Terence Parr
+ All rights reserved.
+
+ Redistribution and use in source and binary forms, with or without
+ modification, are permitted provided that the following conditions
+ are met:
+
+ 1. Redistributions of source code must retain the above copyright
+    notice, this list of conditions and the following disclaimer.
+ 2. Redistributions in binary form must reproduce the above copyright
+    notice, this list of conditions and the following disclaimer in the
+    documentation and/or other materials provided with the distribution.
+ 3. The name of the author may not be used to endorse or promote products
+    derived from this software without specific prior written permission.
+
+ THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+import org.antlr.v4.runtime.ANTLRFileStream;
+import org.antlr.v4.runtime.CommonTokenStream;
+import org.antlr.v4.runtime.ParserRuleContext;
+import org.antlr.v4.runtime.Token;
+import org.antlr.v4.runtime.tree.ParseTreeVisitor;
+import org.antlr.v4.runtime.tree.ParseTreeWalker;
+
+public class TestVisitor {
+	public static class MyVisitor extends ParseTreeVisitor<Integer> implements AVisitor<Integer> {
+		@Override
+		public Integer visit(AParser.AddContext ctx) {
+			return ctx.e(0).dispatch(this) + ctx.e(1).dispatch(this);
+		}
+
+		@Override
+		public Integer visit(AParser.IntContext ctx) {
+			return Integer.valueOf(ctx.INT().getText());
+		}
+
+		@Override
+		public Integer visit(AParser.MultContext ctx) {
+			return ctx.e(0).dispatch(this) * ctx.e(1).dispatch(this);
+		}
+
+		@Override
+		public Integer visit(AParser.ParensContext ctx) {
+			return ctx.e().dispatch(this);
+		}
+
+		@Override
+		public Integer visit(AParser.sContext ctx) {
+			return ctx.e().dispatch(this);
+		}
+	}
+
+	public static void main(String[] args) throws Exception {
+		ALexer lexer = new ALexer(new ANTLRFileStream(args[0]));
+		CommonTokenStream tokens = new CommonTokenStream(lexer);
+		AParser p = new AParser(tokens);
+		p.setBuildParseTree(true);
+		ParserRuleContext<Token> t = p.s();
+		System.out.println("tree = "+t.toStringTree(p));
+
+		MyVisitor visitor = new MyVisitor();
+		Integer result = visitor.visit(t);
+//		Integer result = t.dispatch(visitor);
+		System.out.println("result from tree walk = " + result);
+	}
+}
+

tool/resources/org/antlr/v4/tool/templates/codegen/Java/Java.stg

@@ -551,6 +551,7 @@ public static class <s.name> extends <superClass><if(interfaces)> implements <in
 	}
 <endif>
 	<visitorDispatchMethods; separator="\n">
+        public \<T, V extends <parser.grammarName>Visitor\<T>\> T dispatch(V visitor) { return visitor.visit(this); }
 	<extensionMembers; separator="\n">
 }
 >>
@@ -561,6 +562,7 @@ public static class <s.name> extends <currentRule.name>Context {
 	<getters:{g | <g>}; separator="\n">
 	public <s.name>(<currentRule.name>Context ctx) { copyFrom(ctx); }
 	<visitorDispatchMethods; separator="\n">
+        public \<T, V extends <parser.grammarName>Visitor\<T>\> T dispatch(V visitor) { return visitor.visit(this); }
 }
 >>