Add empty modifier list for pattern variables

pmd-java/etc/grammar/Java.jjt

@@ -329,7 +329,7 @@ class JavaParserImpl {
 
         emptyMods.setDeclaredModifiers(Collections.emptySet());
 
-        JavaccToken tok = getToken(1);
+        JavaccToken tok = JavaccToken.implicitBefore(getToken(1));
         emptyMods.jjtSetFirstToken(tok);
         emptyMods.jjtSetLastToken(tok);
 
@@ -1022,6 +1022,12 @@ void VariableDeclaratorId() :
   <IDENTIFIER> { setLastTokenImage(jjtThis); }
 }
 
+void BindingVarId() #VariableDeclaratorId:
+{ pushEmptyModifierList(); }
+{
+  <IDENTIFIER> { setLastTokenImage(jjtThis); }
+}
+
 void VariableIdWithDims() #VariableDeclaratorId :
 {}
 {
@@ -1500,7 +1506,7 @@ void InstanceOfExpression() #void:
   RelationalExpression() [
     LOOKAHEAD(1)
     ("instanceof"
-        AnnotatedRefType() [ VariableDeclaratorId() #TypeTestPattern(2) ]
+        AnnotatedRefType() [ BindingVarId() #TypeTestPattern(2) ]
         {
             jjtThis.setOp(BinaryOp.INSTANCEOF);
             AbstractJavaNode top = jjtree.popNode();

pmd-java/src/main/java/net/sourceforge/pmd/lang/java/ast/ASTModifierList.java

@@ -111,8 +111,9 @@ public final class ASTModifierList extends AbstractJavaNode {
         return effectiveModifiers;
     }
 
-    public JavaNode getOwner() {
-        return getParent(); // TODO
+    /** Returns the node owning this modifier list. */
+    public AccessNode getOwner() {
+        return (AccessNode) getParent(); // TODO
     }
 
     /**
@@ -209,6 +210,14 @@ public final class ASTModifierList extends AbstractJavaNode {
             }
         }
 
+        @Override
+        public void visit(ASTVariableDeclaratorId node, Set<JModifier> effective) {
+            // resources are implicitly final
+            if (node.isPatternBinding()) {
+                effective.add(FINAL);
+            }
+        }
+
         @Override
         public void visit(ASTLocalVariableDeclaration node, Set<JModifier> effective) {
             // resources are implicitly final
@@ -217,7 +226,6 @@ public final class ASTModifierList extends AbstractJavaNode {
             }
         }
 
-
         @Override
         public void visit(ASTEnumConstant node, Set<JModifier> effective) {
             effective.add(PUBLIC);

pmd-java/src/main/java/net/sourceforge/pmd/lang/java/ast/ASTVariableDeclaratorId.java

@@ -6,6 +6,7 @@ package net.sourceforge.pmd.lang.java.ast;
 
 import java.util.List;
 
+import org.checkerframework.checker.nullness.qual.NonNull;
 import org.checkerframework.checker.nullness.qual.Nullable;
 
 import net.sourceforge.pmd.annotation.Experimental;
@@ -91,8 +92,15 @@ public final class ASTVariableDeclaratorId extends AbstractTypedSymbolDeclarator
         return children(ASTArrayDimensions.class).first();
     }
 
+    @NonNull
     @Override
     public ASTModifierList getModifiers() {
+        if (isPatternBinding()) {
+            JavaNode firstChild = getFirstChild();
+            assert firstChild != null : "Binding variable has no modifiers!";
+            return (ASTModifierList) firstChild;
+        }
+
         // delegates modifiers
         return getModifierOwnerParent().getModifiers();
     }

pmd-java/src/test/kotlin/net/sourceforge/pmd/lang/java/ast/ASTPatternTest.kt

@@ -1,6 +1,7 @@
 package net.sourceforge.pmd.lang.java.ast
 
 import io.kotlintest.matchers.string.shouldContain
+import io.kotlintest.shouldBe
 import net.sourceforge.pmd.lang.ast.test.shouldBe
 import net.sourceforge.pmd.lang.java.ast.JavaVersion.J14__PREVIEW
 import java.io.IOException
@@ -28,7 +29,11 @@ class ASTPatternTest : ParserTestSpec({
                     child<ASTPatternExpression> {
                         it::getPattern shouldBe child<ASTTypeTestPattern> {
                             it::getTypeNode shouldBe classType("Class")
-                            it::getVarId shouldBe variableId("c")
+                            it::getVarId shouldBe variableId("c") {
+                                it::getModifiers shouldBe modifiers {  } // dummy modifier list
+                                it.hasExplicitModifiers(JModifier.FINAL) shouldBe false
+                                it.hasModifiers(JModifier.FINAL) shouldBe true
+                            }
                         }
                     }
                 }