[core] Introduce an AbstractVisitorRule

Remove AntlrBaseRule

docs/pages/pmd/devdocs/major_contributions/adding_a_new_antlr_based_language.md

@@ -154,9 +154,12 @@ definitely don't come for free. It is much effort and requires perseverance to i
 ## 10. Create an abstract rule class for the language
 *   You need to create your own `AbstractRule` in order to interface your language with PMD's generic rule
     execution.
-*   See [`AbstractSwiftRule`](https://github.com/pmd/pmd/blob/pmd/7.0.x/pmd-swift/src/main/java/net/sourceforge/pmd/lang/swift/AbstractSwiftRule.java) as an example.
-*   While the rule basically just extends
-    [`AntlrBaseRule`](https://github.com/pmd/pmd/blob/pmd/7.0.x/pmd-core/src/main/java/net/sourceforge/pmd/lang/ast/impl/antlr4/AntlrBaseRule.java) without adding anything, every language should have its own base class for rule.
+*   See [`AbstractSwiftRule`](https://github.com/pmd/pmd/blob/master/pmd-swift/src/main/java/net/sourceforge/pmd/lang/swift/AbstractSwiftRule.java) as an example.
+*   The rule basically just extends
+    [`AbstractVisitorRule`](https://github.com/pmd/pmd/blob/master/pmd-core/src/main/java/net/sourceforge/pmd/lang/rule/AbstractVisitorRule.java)
+    and only redefines the abstract `buildVisitor()` method to return our own type of visitor.
+    In this case our `SwiftVisitor` is used.
+    While there is no real functionality added, every language should have its own base class for rules.
     This helps to organize the code.
 *   All other rules for your language should extend this class. The purpose of this class is to provide a visitor
     via the method `buildVisitor()` for analyzing the AST. The provided visitor only implements the visit methods

docs/pages/release_notes.md

@@ -43,6 +43,7 @@ The remaining section describe the complete release notes for 7.0.0.
 * Moved the two classes {% jdoc core::cpd.impl.AntlrTokenizer %} and {% jdoc core::cpd.impl.JavaCCTokenizer %} from
   `internal` package into package {% jdoc_package core::cpd.impl %}. These two classes are part of the API and
   are base classes for CPD language implementations.
+* `AntlrBaseRule` is gone in favor of {% jdoc core::pmd.lang.rule.AbstractVisitorRule %}.
 
 #### Fixed Issues:
 * java-codestyle

docs/pages/release_notes_pmd7.md

@@ -752,7 +752,9 @@ until the next major release, but it is recommended to stop using them.
 
 * Moved the two classes {% jdoc core::cpd.impl.AntlrTokenizer %} and {% jdoc core::cpd.impl.JavaCCTokenizer %} from
   `internal` package into package {% jdoc_package core::cpd.impl %}. These two classes are part of the API and
-  are base classes for CPD language implementations.
+  are base classes for CPD language implementations. Since 7.0.0-rc2.
+* `AntlrBaseRule` is gone in favor of {% jdoc core::pmd.lang.rule.AbstractVisitorRule %}. Since 7.0.0-rc2.
+
 
 ### XPath 3.1 support
 

pmd-core/src/main/java/net/sourceforge/pmd/lang/rule/AbstractVisitorRule.java

@@ -2,38 +2,31 @@
  * BSD-style license; for more info see http://pmd.sourceforge.net/license.html
  */
 
-package net.sourceforge.pmd.lang.ast.impl.antlr4;
+package net.sourceforge.pmd.lang.rule;
 
 import net.sourceforge.pmd.RuleContext;
 import net.sourceforge.pmd.lang.ast.AstVisitor;
 import net.sourceforge.pmd.lang.ast.Node;
-import net.sourceforge.pmd.lang.rule.AbstractRule;
-
-/**
- * Base implementation of an antlr rule.
- */
-public abstract class AntlrBaseRule extends AbstractRule {
-
-    protected AntlrBaseRule() {
-        // inheritance constructor
-    }
 
+public abstract class AbstractVisitorRule extends AbstractRule {
     @Override
     public void apply(Node target, RuleContext ctx) {
         AstVisitor<RuleContext, ?> visitor = buildVisitor();
         assert visitor != null : "Rule should provide a non-null visitor";
-        assert target instanceof AntlrNode : "Incorrect node type " + target + " passed to " + this;
 
-        ((AntlrNode<?>) target).acceptVisitor(visitor, ctx);
+        target.acceptVisitor(visitor, ctx);
     }
 
     /**
      * Returns a rule visitor that can visit nodes for the given rule context.
      * This visitor should explore the nodes it's interested in and report
      * violations on the given rule context.
+     * <p>
+     *     Language specific subclasses should redefine the return type to use
+     *     a language specific visitor interface.
+     * </p>
      *
      * @return A visitor bound to the given rule context
      */
     public abstract AstVisitor<RuleContext, ?> buildVisitor();
-
 }

pmd-kotlin/src/main/java/net/sourceforge/pmd/lang/kotlin/AbstractKotlinRule.java

@@ -5,10 +5,10 @@
 package net.sourceforge.pmd.lang.kotlin;
 
 import net.sourceforge.pmd.RuleContext;
-import net.sourceforge.pmd.lang.ast.impl.antlr4.AntlrBaseRule;
 import net.sourceforge.pmd.lang.kotlin.ast.KotlinVisitor;
+import net.sourceforge.pmd.lang.rule.AbstractVisitorRule;
 
-public abstract class AbstractKotlinRule extends AntlrBaseRule {
+public abstract class AbstractKotlinRule extends AbstractVisitorRule {
 
     protected AbstractKotlinRule() {
         // inheritance constructor

pmd-swift/src/main/java/net/sourceforge/pmd/lang/swift/AbstractSwiftRule.java

@@ -5,15 +5,15 @@
 package net.sourceforge.pmd.lang.swift;
 
 import net.sourceforge.pmd.RuleContext;
-import net.sourceforge.pmd.lang.ast.AstVisitor;
-import net.sourceforge.pmd.lang.ast.impl.antlr4.AntlrBaseRule;
+import net.sourceforge.pmd.lang.rule.AbstractVisitorRule;
+import net.sourceforge.pmd.lang.swift.ast.SwiftVisitor;
 
-public abstract class AbstractSwiftRule extends AntlrBaseRule {
+public abstract class AbstractSwiftRule extends AbstractVisitorRule {
 
     protected AbstractSwiftRule() {
         // inheritance constructor
     }
 
     @Override
-    public abstract AstVisitor<RuleContext, ?> buildVisitor();
+    public abstract SwiftVisitor<RuleContext, ?> buildVisitor();
 }

pmd-swift/src/main/java/net/sourceforge/pmd/lang/swift/rule/bestpractices/UnavailableFunctionRule.java

@@ -7,7 +7,6 @@ package net.sourceforge.pmd.lang.swift.rule.bestpractices;
 import java.util.List;
 
 import net.sourceforge.pmd.RuleContext;
-import net.sourceforge.pmd.lang.ast.AstVisitor;
 import net.sourceforge.pmd.lang.swift.AbstractSwiftRule;
 import net.sourceforge.pmd.lang.swift.ast.SwiftParser.SwAttribute;
 import net.sourceforge.pmd.lang.swift.ast.SwiftParser.SwAttributes;
@@ -15,6 +14,7 @@ import net.sourceforge.pmd.lang.swift.ast.SwiftParser.SwCodeBlock;
 import net.sourceforge.pmd.lang.swift.ast.SwiftParser.SwFunctionDeclaration;
 import net.sourceforge.pmd.lang.swift.ast.SwiftParser.SwInitializerDeclaration;
 import net.sourceforge.pmd.lang.swift.ast.SwiftParser.SwStatement;
+import net.sourceforge.pmd.lang.swift.ast.SwiftVisitor;
 import net.sourceforge.pmd.lang.swift.ast.SwiftVisitorBase;
 
 public class UnavailableFunctionRule extends AbstractSwiftRule {
@@ -29,7 +29,7 @@ public class UnavailableFunctionRule extends AbstractSwiftRule {
     }
 
     @Override
-    public AstVisitor<RuleContext, ?> buildVisitor() {
+    public SwiftVisitor<RuleContext, ?> buildVisitor() {
         return new SwiftVisitorBase<RuleContext, Void>() {
 
             @Override