Handle final variables in instanceof patterns

core/src/main/java/com/google/googlejavaformat/java/java14/Java14InputAstVisitor.java

@@ -27,6 +27,7 @@
 import com.sun.source.tree.ClassTree;
 import com.sun.source.tree.ExpressionTree;
 import com.sun.source.tree.InstanceOfTree;
+import com.sun.source.tree.ModifiersTree;
 import com.sun.source.tree.SwitchExpressionTree;
 import com.sun.source.tree.Tree;
 import com.sun.source.tree.VariableTree;
@@ -56,12 +57,13 @@ public Void visitBindingPattern(BindingPatternTree node, Void unused) {
     try {
       VariableTree variableTree =
           (VariableTree) BindingPatternTree.class.getMethod("getVariable").invoke(node);
-      visitBindingPattern(variableTree.getType(), variableTree.getName());
+      visitBindingPattern(
+          variableTree.getModifiers(), variableTree.getType(), variableTree.getName());
     } catch (ReflectiveOperationException e1) {
       try {
         Tree type = (Tree) BindingPatternTree.class.getMethod("getType").invoke(node);
         Name name = (Name) BindingPatternTree.class.getMethod("getName").invoke(node);
-        visitBindingPattern(type, name);
+        visitBindingPattern(/* modifiers= */ null, type, name);
       } catch (ReflectiveOperationException e2) {
         e2.addSuppressed(e1);
         throw new LinkageError(e2.getMessage(), e2);
@@ -70,7 +72,10 @@ public Void visitBindingPattern(BindingPatternTree node, Void unused) {
     return null;
   }
 
-  private void visitBindingPattern(Tree type, Name name) {
+  private void visitBindingPattern(ModifiersTree modifiers, Tree type, Name name) {
+    if (modifiers != null) {
+      builder.addAll(visitModifiers(modifiers, Direction.HORIZONTAL, Optional.empty()));
+    }
     scan(type, null);
     builder.breakOp(" ");
     visit(name);

core/src/test/java/com/google/googlejavaformat/java/FormatterIntegrationTest.java

@@ -50,6 +50,8 @@ public class FormatterIntegrationTest {
   private static final ImmutableSet<String> JAVA14_TESTS =
       ImmutableSet.of("I477", "Records", "RSLs", "Var", "ExpressionSwitch");
 
+  private static final ImmutableSet<String> JAVA16_TESTS = ImmutableSet.of("I588");
+
   @Parameters(name = "{index}: {0}")
   public static Iterable<Object[]> data() throws IOException {
     Path testDataPath = Paths.get("com/google/googlejavaformat/java/testdata");
@@ -76,7 +78,7 @@ public static Iterable<Object[]> data() throws IOException {
           case "output":
             outputs.put(baseName, contents);
             break;
-          default:
+          default: // fall out
         }
       }
     }
@@ -90,6 +92,9 @@ public static Iterable<Object[]> data() throws IOException {
       if (JAVA14_TESTS.contains(fileName) && getMajor() < 14) {
         continue;
       }
+      if (JAVA16_TESTS.contains(fileName) && getMajor() < 16) {
+        continue;
+      }
       testInputs.add(new Object[] {fileName, input, expectedOutput});
     }
     return testInputs;

core/src/test/resources/com/google/googlejavaformat/java/testdata/I588.input

@@ -0,0 +1,8 @@
+class T {
+  int f(Object x) {
+    if (x instanceof final Integer i) {
+      return i;
+    }
+    return -1;
+  }
+}

core/src/test/resources/com/google/googlejavaformat/java/testdata/I588.output

@@ -0,0 +1,8 @@
+class T {
+  int f(Object x) {
+    if (x instanceof final Integer i) {
+      return i;
+    }
+    return -1;
+  }
+}