Handled all steps of "Adding PMD support for a new ANTLR grammar based language" except $. Generate your Parser did not succeed because combining lexer and parser grammars has issues.

pmd-kotlin/src/main/antlr4/net/sourceforge/pmd/lang/kotlin/ast/PmdKotlinParser.java

@@ -0,0 +1,28 @@
+/*
+ * BSD-style license; for more info see http://pmd.sourceforge.net/license.html
+ */
+
+package net.sourceforge.pmd.lang.kotlin.ast;
+
+import net.sourceforge.pmd.lang.ast.impl.antlr4.AntlrBaseParser;
+import net.sourceforge.pmd.lang.kotlin.ast.KotlinParser.KtTopLevel;
+import org.antlr.v4.runtime.CharStream;
+import org.antlr.v4.runtime.CommonTokenStream;
+import org.antlr.v4.runtime.Lexer;
+
+/**
+ * Adapter for the KotlinParser.
+ */
+public final class PmdKotlinParser extends AntlrBaseParser<KotlinNode, KtTopLevel> {
+
+    @Override
+    protected KtTopLevel parse(final Lexer lexer, ParserTask task) {
+        KotlinParser parser = new KotlinParser(new CommonTokenStream(lexer));
+        return parser.topLevel().makeAstInfo(task);
+    }
+
+    @Override
+    protected Lexer getLexer(final CharStream source) {
+        return new KotlinLexer(source);
+    }
+}

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

@@ -0,0 +1,19 @@
+/**
+ * BSD-style license; for more info see http://pmd.sourceforge.net/license.html
+ */
+
+package net.sourceforge.pmd.lang.kotlin;
+
+import net.sourceforge.pmd.RuleContext;
+import net.sourceforge.pmd.lang.ast.AstVisitor;
+import net.sourceforge.pmd.lang.ast.impl.antlr4.AntlrBaseRule;
+
+public abstract class AbstractKotlinRule extends AntlrBaseRule {
+
+    protected AbstractKotlinRule() {
+        // inheritance constructor
+    }
+
+    @Override
+    public abstract AstVisitor<RuleContext, ?> buildVisitor();
+}

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

@@ -0,0 +1,25 @@
+/**
+ * BSD-style license; for more info see http://pmd.sourceforge.net/license.html
+ */
+
+package net.sourceforge.pmd.lang.kotlin;
+
+import net.sourceforge.pmd.lang.AbstractPmdLanguageVersionHandler;
+import net.sourceforge.pmd.lang.ast.Parser;
+import net.sourceforge.pmd.lang.kotlin.ast.PmdKotlinParser;
+
+
+public class KotlinHandler extends AbstractPmdLanguageVersionHandler {
+
+    private final String kotlinRelease;
+
+    public KotlinHandler(String release) {
+        kotlinRelease = release;
+        // check language version?
+    }
+
+    @Override
+    public Parser getParser() {
+        return new PmdKotlinParser();
+    }
+}

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

@@ -0,0 +1,28 @@
+/**
+ * BSD-style license; for more info see http://pmd.sourceforge.net/license.html
+ */
+
+package net.sourceforge.pmd.lang.kotlin;
+
+import net.sourceforge.pmd.lang.BaseLanguageModule;
+
+/**
+ * Language Module for Kotlin
+ */
+public class KotlinLanguageModule extends BaseLanguageModule {
+
+    /** The name. */
+    public static final String NAME = "Kotlin";
+    /** The terse name. */
+    public static final String TERSE_NAME = "kotlin";
+
+    /**
+     * Create a new instance of Kotlin Language Module.
+     */
+    public KotlinLanguageModule() {
+        super(NAME, null, TERSE_NAME, "kt", "ktm");
+        addVersion("", new KotlinHandler("1.3"));
+        addVersion("", new KotlinHandler("1.4"));
+        addDefaultVersion("", new KotlinHandler("1.5"));
+    }
+}

pmd-kotlin/src/main/java/net/sourceforge/pmd/lang/kotlin/ast/KotlinVisitorBase.java

@@ -0,0 +1,14 @@
+/*
+ * BSD-style license; for more info see http://pmd.sourceforge.net/license.html
+ */
+
+package net.sourceforge.pmd.lang.kotlin.ast;
+
+import net.sourceforge.pmd.lang.ast.AstVisitorBase;
+
+/**
+ * Base class for kotlin visitors.
+ */
+public abstract class KotlinVisitorBase<P, R> extends AstVisitorBase<P, R> implements KotlinVisitor<P, R> {
+
+}