Leverage basic Java 17 features (#451)

- Refactor code to use the following basic Java 17 features:
  - pattern matching for instanceof
  - @Serial annotation
  - switch expressions
  - enhanced switch statements
  - StringBuilder.isEmpty()
- Replace two switch statements with simpler if statements.
- Rename a few local variables.

bench/src/jmh/java/org/pkl/core/ListSort.java

@@ -111,10 +111,10 @@ public class ListSort {
                 // append `.length` to avoid rendering the list
                 new ReplRequest.Eval("sort", "nums.sortWith(cmp).length", false, false))
             .get(0);
-    if (!(response instanceof ReplResponse.EvalSuccess)) {
+    if (!(response instanceof ReplResponse.EvalSuccess success)) {
       throw new AssertionError(response);
     }
-    return ((ReplResponse.EvalSuccess) response).getResult();
+    return success.getResult();
   }
 
   // note that this is an uneven comparison

pkl-config-java/src/main/java/org/pkl/config/java/AbstractConfig.java

@@ -38,11 +38,11 @@ abstract class AbstractConfig implements Config {
   public Config get(String propertyName) {
     var childValue = getRawChildValue(propertyName);
     var childName = qualifiedName.isEmpty() ? propertyName : qualifiedName + '.' + propertyName;
-    if (childValue instanceof Composite) {
+    if (childValue instanceof Composite composite) {
-      return new CompositeConfig(childName, mapper, (Composite) childValue);
+      return new CompositeConfig(childName, mapper, composite);
     }
-    if (childValue instanceof Map) {
+    if (childValue instanceof Map<?, ?> map) {
-      return new MapConfig(childName, mapper, (Map<?, ?>) childValue);
+      return new MapConfig(childName, mapper, map);
     }
     return new LeafConfig(childName, mapper, childValue);
   }

pkl-config-java/src/main/java/org/pkl/config/java/JavaType.java

@@ -49,10 +49,10 @@ public class JavaType<T> {
 
   protected JavaType() {
     var superclass = getClass().getGenericSuperclass();
-    if (superclass instanceof Class) {
+    if (!(superclass instanceof ParameterizedType parameterizedType)) {
       throw new IllegalStateException("JavaType token must be parameterized.");
     }
-    type = ((ParameterizedType) superclass).getActualTypeArguments()[0];
+    type = parameterizedType.getActualTypeArguments()[0];
   }
 
   private JavaType(Type type) {
@@ -161,9 +161,7 @@ public class JavaType<T> {
   @Override
   public boolean equals(@Nullable Object obj) {
     if (this == obj) return true;
-    if (!(obj instanceof JavaType)) return false;
+    if (!(obj instanceof JavaType<?> other)) return false;
-
-    var other = (JavaType<?>) obj;
     return type.equals(other.type);
   }
 

pkl-config-java/src/main/java/org/pkl/config/java/mapper/PNullToAny.java

@@ -23,7 +23,7 @@ final class PNullToAny implements ConverterFactory {
   @Override
   public Optional<Converter<?, ?>> create(PClassInfo<?> sourceType, Type targetType) {
     if (sourceType != PClassInfo.Null
-        || (targetType instanceof Class && ((Class<?>) targetType).isPrimitive())) {
+        || (targetType instanceof Class<?> clazz && clazz.isPrimitive())) {
       return Optional.empty();
     }
 

pkl-config-java/src/main/java/org/pkl/config/java/mapper/Reflection.java

@@ -46,8 +46,7 @@ public final class Reflection {
   }
 
   public static boolean isMissingTypeArguments(Type type) {
-    if (type instanceof WildcardType) {
+    if (type instanceof WildcardType wildcardType) {
-      var wildcardType = (WildcardType) type;
       var baseType =
           wildcardType.getLowerBounds().length > 0
               ? wildcardType.getLowerBounds()[0]
@@ -62,11 +61,10 @@ public final class Reflection {
    * instantiable (not an interface or abstract class).
    */
   public static Type normalize(Type type) {
-    if (type instanceof WildcardType) {
+    if (type instanceof WildcardType wildcardType) {
-      var wcType = (WildcardType) type;
+      var bounds = wildcardType.getLowerBounds();
-      var bounds = wcType.getLowerBounds();
       if (bounds.length > 0) return bounds[0];
-      bounds = wcType.getUpperBounds();
+      bounds = wildcardType.getUpperBounds();
       if (bounds.length > 0) return bounds[0];
     }
     return getExactSupertype(type, toRawType(type));
@@ -154,8 +152,8 @@ public final class Reflection {
    * eliminate them.
    */
   private static Type uncapture(Type type) {
-    if (type instanceof CaptureType) {
+    if (type instanceof CaptureType captureType) {
-      return ((CaptureType) type).getWildcardType();
+      return captureType.getWildcardType();
     }
     return type;
   }

pkl-config-java/src/main/java/org/pkl/config/java/mapper/Tuple2.java

@@ -35,10 +35,7 @@ final class Tuple2<S, T> {
   @Override
   public boolean equals(@Nullable Object obj) {
     if (this == obj) return true;
-    if (!(obj instanceof Tuple2)) return false;
+    if (!(obj instanceof Tuple2<?, ?> other)) return false;
-
-    var other = (Tuple2<?, ?>) obj;
-
     return first.equals(other.first) && second.equals(other.second);
   }
 

pkl-config-java/src/main/java/org/pkl/config/java/mapper/TypeMapping.java

@@ -59,9 +59,7 @@ public final class TypeMapping<S, T extends S> {
   @Override
   public boolean equals(@Nullable Object obj) {
     if (this == obj) return true;
-    if (!(obj instanceof TypeMapping)) return false;
+    if (!(obj instanceof TypeMapping<?, ?> other)) return false;
-
-    var other = (TypeMapping<?, ?>) obj;
     return requestedType == other.requestedType && implementationType == other.implementationType;
   }
 

pkl-config-java/src/main/java/org/pkl/config/java/mapper/Types.java

@@ -44,8 +44,7 @@ public final class Types {
               typeParamsCount, rawType.getTypeName(), typeArguments.length));
     }
     for (Type arg : typeArguments) {
-      if (arg instanceof Class) {
+      if (arg instanceof Class<?> clazz) {
-        var clazz = (Class<?>) arg;
         if (clazz.isPrimitive()) {
           throw new IllegalArgumentException(
               String.format(

pkl-config-java/src/main/java/org/pkl/config/java/mapper/ValueMapperBuilder.java

@@ -64,8 +64,7 @@ public final class ValueMapperBuilder {
   @SuppressWarnings({"unchecked", "rawtypes"})
   public ValueMapperBuilder addConversion(Conversion<?, ?> conversion) {
     conversions.add(conversion);
-    if (conversion.targetType instanceof Class) {
+    if (conversion.targetType instanceof Class<?> clazz) {
-      var clazz = (Class<?>) conversion.targetType;
       if (clazz.isPrimitive()) {
         conversions.add(
             Conversion.of(

pkl-config-java/src/test/java/org/pkl/config/java/mapper/PObjectToDataObjectJavaxInjectTest.java

@@ -91,9 +91,7 @@ public class PObjectToDataObjectJavaxInjectTest {
     @Override
     public boolean equals(@Nullable Object obj) {
       if (this == obj) return true;
-      if (!(obj instanceof Person)) return false;
+      if (!(obj instanceof Person other)) return false;
-
-      var other = (Person) obj;
       return name.equals(other.name)
           && age == other.age
           && hobbies.equals(other.hobbies)
@@ -118,9 +116,7 @@ public class PObjectToDataObjectJavaxInjectTest {
     @Override
     public boolean equals(@Nullable Object obj) {
       if (this == obj) return true;
-      if (!(obj instanceof Address)) return false;
+      if (!(obj instanceof Address other)) return false;
-
-      var other = (Address) obj;
       return street.equals(other.street) && zip == other.zip;
     }
 
@@ -148,9 +144,7 @@ public class PObjectToDataObjectJavaxInjectTest {
     @Override
     public boolean equals(@Nullable Object obj) {
       if (this == obj) return true;
-      if (!(obj instanceof Pair)) return false;
+      if (!(obj instanceof Pair<?, ?> other)) return false;
-
-      var other = (Pair<?, ?>) obj;
       return first.equals(other.first) && second.equals(other.second);
     }
 

pkl-config-java/src/test/java/org/pkl/config/java/mapper/PObjectToDataObjectTest.java

@@ -136,9 +136,7 @@ public class PObjectToDataObjectTest {
     @Override
     public boolean equals(@Nullable Object obj) {
       if (this == obj) return true;
-      if (!(obj instanceof Person)) return false;
+      if (!(obj instanceof Person other)) return false;
-
-      var other = (Person) obj;
       return name.equals(other.name)
           && age == other.age
           && hobbies.equals(other.hobbies)
@@ -168,9 +166,7 @@ public class PObjectToDataObjectTest {
     @Override
     public boolean equals(@Nullable Object obj) {
       if (this == obj) return true;
-      if (!(obj instanceof PersonConstructoProperties)) return false;
+      if (!(obj instanceof PersonConstructoProperties other)) return false;
-
-      var other = (PersonConstructoProperties) obj;
       return name.equals(other.name)
           && age == other.age
           && hobbies.equals(other.hobbies)
@@ -195,9 +191,7 @@ public class PObjectToDataObjectTest {
     @Override
     public boolean equals(@Nullable Object obj) {
       if (this == obj) return true;
-      if (!(obj instanceof Address)) return false;
+      if (!(obj instanceof Address other)) return false;
-
-      var other = (Address) obj;
       return street.equals(other.street) && zip == other.zip;
     }
 
@@ -225,9 +219,7 @@ public class PObjectToDataObjectTest {
     @Override
     public boolean equals(@Nullable Object obj) {
       if (this == obj) return true;
-      if (!(obj instanceof Pair)) return false;
+      if (!(obj instanceof Pair<?, ?> other)) return false;
-
-      var other = (Pair<?, ?>) obj;
       return first.equals(other.first) && second.equals(other.second);
     }
 

pkl-config-java/src/test/java/org/pkl/config/java/mapper/Person.java

@@ -29,9 +29,7 @@ public class Person {
   @Override
   public boolean equals(@Nullable Object obj) {
     if (this == obj) return true;
-    if (!(obj instanceof Person)) return false;
+    if (!(obj instanceof Person other)) return false;
-
-    var other = (Person) obj;
     return name.equals(other.name) && age == other.age;
   }
 

pkl-core/src/main/java/org/pkl/core/DataSize.java

@@ -17,13 +17,14 @@ package org.pkl.core;
 
 import static org.pkl.core.DataSizeUnit.*;
 
+import java.io.Serial;
 import java.util.Objects;
 import org.pkl.core.util.MathUtils;
 import org.pkl.core.util.Nullable;
 
 /** Java representation of a {@code pkl.base#DataSize} value. */
 public final class DataSize implements Value {
-  private static final long serialVersionUID = 0L;
+  @Serial private static final long serialVersionUID = 0L;
 
   private final double value;
   private final DataSizeUnit unit;
@@ -240,9 +241,7 @@ public final class DataSize implements Value {
   @Override
   public boolean equals(@Nullable Object obj) {
     if (this == obj) return true;
-    if (!(obj instanceof DataSize)) return false;
+    if (!(obj instanceof DataSize other)) return false;
-
-    var other = (DataSize) obj;
     return convertValueTo(DataSizeUnit.BYTES) == other.convertValueTo(DataSizeUnit.BYTES);
   }
 

pkl-core/src/main/java/org/pkl/core/DataSizeUnit.java

@@ -48,32 +48,20 @@ public enum DataSizeUnit {
    * exists.
    */
   public static @Nullable DataSizeUnit parse(String symbol) {
-    switch (symbol) {
+    return switch (symbol) {
-      case "b":
+      case "b" -> BYTES;
-        return BYTES;
+      case "kb" -> KILOBYTES;
-      case "kb":
+      case "kib" -> KIBIBYTES;
-        return KILOBYTES;
+      case "mb" -> MEGABYTES;
-      case "kib":
+      case "mib" -> MEBIBYTES;
-        return KIBIBYTES;
+      case "gb" -> GIGABYTES;
-      case "mb":
+      case "gib" -> GIBIBYTES;
-        return MEGABYTES;
+      case "tb" -> TERABYTES;
-      case "mib":
+      case "tib" -> TEBIBYTES;
-        return MEBIBYTES;
+      case "pb" -> PETABYTES;
-      case "gb":
+      case "pib" -> PEBIBYTES;
-        return GIGABYTES;
+      default -> null;
-      case "gib":
+    };
-        return GIBIBYTES;
-      case "tb":
-        return TERABYTES;
-      case "tib":
-        return TEBIBYTES;
-      case "pb":
-        return PETABYTES;
-      case "pib":
-        return PEBIBYTES;
-      default:
-        return null;
-    }
   }
 
   /** Returns the String symbol of this unit. */

pkl-core/src/main/java/org/pkl/core/Duration.java

@@ -17,13 +17,14 @@ package org.pkl.core;
 
 import static org.pkl.core.DurationUnit.*;
 
+import java.io.Serial;
 import java.util.Objects;
 import org.pkl.core.util.DurationUtils;
 import org.pkl.core.util.Nullable;
 
 /** Java representation of a {@code pkl.base#Duration} value. */
 public final class Duration implements Value {
-  private static final long serialVersionUID = 0L;
+  @Serial private static final long serialVersionUID = 0L;
 
   private final double value;
   private final DurationUnit unit;
@@ -215,9 +216,7 @@ public final class Duration implements Value {
   @Override
   public boolean equals(@Nullable Object obj) {
     if (this == obj) return true;
-    if (!(obj instanceof Duration)) return false;
+    if (!(obj instanceof Duration other)) return false;
-
-    var other = (Duration) obj;
     return convertValueTo(DurationUnit.NANOS) == other.convertValueTo(DurationUnit.NANOS);
   }
 

pkl-core/src/main/java/org/pkl/core/DurationUnit.java

@@ -46,24 +46,16 @@ public enum DurationUnit {
    * exists.
    */
   public static @Nullable DurationUnit parse(String symbol) {
-    switch (symbol) {
+    return switch (symbol) {
-      case "ns":
+      case "ns" -> NANOS;
-        return NANOS;
+      case "us" -> MICROS;
-      case "us":
+      case "ms" -> MILLIS;
-        return MICROS;
+      case "s" -> SECONDS;
-      case "ms":
+      case "min" -> MINUTES;
-        return MILLIS;
+      case "h" -> HOURS;
-      case "s":
+      case "d" -> DAYS;
-        return SECONDS;
+      default -> null;
-      case "min":
+    };
-        return MINUTES;
-      case "h":
-        return HOURS;
-      case "d":
-        return DAYS;
-      default:
-        return null;
-    }
   }
 
   /** Returns the string symbol of this unit. */
@@ -78,24 +70,15 @@ public enum DurationUnit {
 
   /** Converts this unit to a {@link java.time.temporal.ChronoUnit}. */
   public ChronoUnit toChronoUnit() {
-    switch (this) {
+    return switch (this) {
-      case NANOS:
+      case NANOS -> ChronoUnit.NANOS;
-        return ChronoUnit.NANOS;
+      case MICROS -> ChronoUnit.MICROS;
-      case MICROS:
+      case MILLIS -> ChronoUnit.MILLIS;
-        return ChronoUnit.MICROS;
+      case SECONDS -> ChronoUnit.SECONDS;
-      case MILLIS:
+      case MINUTES -> ChronoUnit.MINUTES;
-        return ChronoUnit.MILLIS;
+      case HOURS -> ChronoUnit.HOURS;
-      case SECONDS:
+      case DAYS -> ChronoUnit.DAYS;
-        return ChronoUnit.SECONDS;
+    };
-      case MINUTES:
-        return ChronoUnit.MINUTES;
-      case HOURS:
-        return ChronoUnit.HOURS;
-      case DAYS:
-        return ChronoUnit.DAYS;
-      default:
-        throw new AssertionError("Unknown duration unit: " + this);
-    }
   }
 
   /** Converts this unit to a {@link java.util.concurrent.TimeUnit}. */

pkl-core/src/main/java/org/pkl/core/EvaluatorImpl.java

@@ -148,8 +148,7 @@ public class EvaluatorImpl implements Evaluator {
         (module) -> {
           var output = (VmTyped) VmUtils.readMember(module, Identifier.OUTPUT);
           var value = VmUtils.readMember(output, Identifier.VALUE);
-          if (value instanceof VmValue) {
+          if (value instanceof VmValue vmValue) {
-            var vmValue = (VmValue) value;
             vmValue.force(false);
             return vmValue.export();
           }
@@ -194,8 +193,7 @@ public class EvaluatorImpl implements Evaluator {
         (module) -> {
           var expressionResult =
               VmUtils.evaluateExpression(module, expression, securityManager, moduleResolver);
-          if (expressionResult instanceof VmValue) {
+          if (expressionResult instanceof VmValue value) {
-            var value = (VmValue) expressionResult;
             value.force(false);
             return value.export();
           }
@@ -248,8 +246,7 @@ public class EvaluatorImpl implements Evaluator {
           var value = VmUtils.readMember(output, Identifier.VALUE);
           var valueClassInfo = VmUtils.getClass(value).getPClassInfo();
           if (valueClassInfo.equals(classInfo)) {
-            if (value instanceof VmValue) {
+            if (value instanceof VmValue vmValue) {
-              var vmValue = (VmValue) value;
               vmValue.force(false);
               //noinspection unchecked
               return (T) vmValue.export();
@@ -317,10 +314,10 @@ public class EvaluatorImpl implements Evaluator {
     } catch (Exception e) {
       throw new PklBugException(e);
     } catch (ExceptionInInitializerError e) {
-      if (!(e.getCause() instanceof VmException)) {
+      if (!(e.getCause() instanceof VmException vmException)) {
         throw new PklBugException(e);
       }
-      var pklException = ((VmException) e.getCause()).toPklException(frameTransformer);
+      var pklException = vmException.toPklException(frameTransformer);
       var error = new ExceptionInInitializerError(pklException);
       error.setStackTrace(e.getStackTrace());
       throw new PklBugException(error);

pkl-core/src/main/java/org/pkl/core/Member.java

@@ -15,6 +15,7 @@
  */
 package org.pkl.core;
 
+import java.io.Serial;
 import java.io.Serializable;
 import java.util.List;
 import java.util.Objects;
@@ -23,8 +24,7 @@ import org.pkl.core.util.Nullable;
 
 /** Common base class for TypeAlias, PClass, PClass.Property, and PClass.Method. */
 public abstract class Member implements Serializable {
-
+  @Serial private static final long serialVersionUID = 0L;
-  private static final long serialVersionUID = 0L;
 
   private final @Nullable String docComment;
   private final SourceLocation sourceLocation;
@@ -99,8 +99,7 @@ public abstract class Member implements Serializable {
   }
 
   public static class SourceLocation implements Serializable {
-
+    @Serial private static final long serialVersionUID = 0L;
-    private static final long serialVersionUID = 0L;
 
     private final int startLine;
     private final int endLine;

pkl-core/src/main/java/org/pkl/core/PClass.java

@@ -15,12 +15,13 @@
  */
 package org.pkl.core;
 
+import java.io.Serial;
 import java.util.*;
 import org.pkl.core.util.Nullable;
 
 /** Java representation of a {@code pkl.base#Class} value. */
 public final class PClass extends Member implements Value {
-  private static final long serialVersionUID = 0L;
+  @Serial private static final long serialVersionUID = 0L;
 
   private final PClassInfo<?> classInfo;
   private final List<TypeParameter> typeParameters;
@@ -138,8 +139,7 @@ public final class PClass extends Member implements Value {
   }
 
   public abstract static class ClassMember extends Member {
-
+    @Serial private static final long serialVersionUID = 0L;
-    private static final long serialVersionUID = 0L;
 
     private final PClass owner;
 
@@ -176,8 +176,7 @@ public final class PClass extends Member implements Value {
   }
 
   public static final class Property extends ClassMember {
-
+    @Serial private static final long serialVersionUID = 0L;
-    private static final long serialVersionUID = 0L;
 
     private final PType type;
 
@@ -213,8 +212,7 @@ public final class PClass extends Member implements Value {
   }
 
   public static final class Method extends ClassMember {
-
+    @Serial private static final long serialVersionUID = 0L;
-    private static final long serialVersionUID = 0L;
 
     private final List<TypeParameter> typeParameters;
     private final Map<String, PType> parameters;

pkl-core/src/main/java/org/pkl/core/PClassInfo.java

@@ -17,6 +17,7 @@ package org.pkl.core;
 
 import static java.util.Map.*;
 
+import java.io.Serial;
 import java.io.Serializable;
 import java.net.URI;
 import java.util.*;
@@ -26,8 +27,7 @@ import org.pkl.core.util.Nullable;
 /** Information about a Pkl class and its Java representation. */
 @SuppressWarnings("rawtypes")
 public final class PClassInfo<T> implements Serializable {
-
+  @Serial private static final long serialVersionUID = 0L;
-  private static final long serialVersionUID = 0L;
 
   // Simple name of a module's class.
   // User-facing via `module.getClass()` and error messages.
@@ -100,7 +100,7 @@ public final class PClassInfo<T> implements Serializable {
   /** Returns the class info for the given value's class. */
   @SuppressWarnings("unchecked")
   public static <T> PClassInfo<T> forValue(T value) {
-    if (value instanceof Value) return (PClassInfo<T>) ((Value) value).getClassInfo();
+    if (value instanceof Value v) return (PClassInfo<T>) v.getClassInfo();
 
     if (value instanceof String) return (PClassInfo<T>) String;
     if (value instanceof Boolean) return (PClassInfo<T>) Boolean;
@@ -179,9 +179,7 @@ public final class PClassInfo<T> implements Serializable {
 
   public boolean equals(@Nullable Object obj) {
     if (this == obj) return true;
-    if (!(obj instanceof PClassInfo)) return false;
+    if (!(obj instanceof PClassInfo<?> other)) return false;
-
-    var other = (PClassInfo<?>) obj;
     return qualifiedName.equals(other.qualifiedName);
   }
 

pkl-core/src/main/java/org/pkl/core/PModule.java

@@ -15,6 +15,7 @@
  */
 package org.pkl.core;
 
+import java.io.Serial;
 import java.net.URI;
 import java.util.Map;
 import java.util.Objects;
@@ -22,7 +23,7 @@ import org.pkl.core.util.Nullable;
 
 /** Java representation of a Pkl module. */
 public final class PModule extends PObject {
-  private static final long serialVersionUID = 0L;
+  @Serial private static final long serialVersionUID = 0L;
 
   private final URI moduleUri;
   private final String moduleName;
@@ -62,10 +63,7 @@ public final class PModule extends PObject {
   @Override
   public boolean equals(@Nullable Object obj) {
     if (this == obj) return true;
-    if (!(obj instanceof PModule)) return false;
+    if (!(obj instanceof PModule other)) return false;
-
-    var other = (PModule) obj;
-
     return moduleUri.equals(other.moduleUri)
         && moduleName.equals(other.moduleName)
         && classInfo.equals(other.classInfo)

pkl-core/src/main/java/org/pkl/core/PNull.java

@@ -15,9 +15,11 @@
  */
 package org.pkl.core;
 
+import java.io.Serial;
+
 /** Java representation of a {@code pkl.base#Null} value. */
 public final class PNull implements Value {
-  private static final long serialVersionUID = 0L;
+  @Serial private static final long serialVersionUID = 0L;
   private static final PNull INSTANCE = new PNull();
 
   /** Returns the sole instance of this class. */

pkl-core/src/main/java/org/pkl/core/PObject.java

@@ -15,13 +15,14 @@
  */
 package org.pkl.core;
 
+import java.io.Serial;
 import java.util.Map;
 import java.util.Objects;
 import org.pkl.core.util.Nullable;
 
 /** Java representation of a Pkl object. */
 public class PObject implements Composite {
-  private static final long serialVersionUID = 0L;
+  @Serial private static final long serialVersionUID = 0L;
 
   protected final PClassInfo<?> classInfo;
   protected final Map<String, Object> properties;

pkl-core/src/main/java/org/pkl/core/PType.java

@@ -15,30 +15,30 @@
  */
 package org.pkl.core;
 
+import java.io.Serial;
 import java.io.Serializable;
 import java.util.*;
 
 /** A Pkl type as used in type annotations. */
 public abstract class PType implements Serializable {
-
+  @Serial private static final long serialVersionUID = 0L;
-  private static final long serialVersionUID = 0L;
 
   /** The `unknown` type. Omitting a type annotation is equivalent to stating this type. */
   public static final PType UNKNOWN =
       new PType() {
-        private static final long serialVersionUID = 0L;
+        @Serial private static final long serialVersionUID = 0L;
       };
 
   /** The bottom type. */
   public static final PType NOTHING =
       new PType() {
-        private static final long serialVersionUID = 0L;
+        @Serial private static final long serialVersionUID = 0L;
       };
 
   /** The type of the enclosing module. */
   public static final PType MODULE =
       new PType() {
-        private static final long serialVersionUID = 0L;
+        @Serial private static final long serialVersionUID = 0L;
       };
 
   private PType() {}
@@ -48,8 +48,7 @@ public abstract class PType implements Serializable {
   }
 
   public static final class StringLiteral extends PType {
-
+    @Serial private static final long serialVersionUID = 0L;
-    private static final long serialVersionUID = 0L;
 
     private final String literal;
 
@@ -63,8 +62,7 @@ public abstract class PType implements Serializable {
   }
 
   public static final class Class extends PType {
-
+    @Serial private static final long serialVersionUID = 0L;
-    private static final long serialVersionUID = 0L;
 
     private final PClass pClass;
     private final List<PType> typeArguments;
@@ -97,8 +95,7 @@ public abstract class PType implements Serializable {
   }
 
   public static final class Nullable extends PType {
-
+    @Serial private static final long serialVersionUID = 0L;
-    private static final long serialVersionUID = 0L;
 
     private final PType baseType;
 
@@ -133,8 +130,7 @@ public abstract class PType implements Serializable {
   }
 
   public static final class Alias extends PType {
-
+    @Serial private static final long serialVersionUID = 0L;
-    private static final long serialVersionUID = 0L;
 
     private final TypeAlias typeAlias;
     private final List<PType> typeArguments;
@@ -169,8 +165,7 @@ public abstract class PType implements Serializable {
   }
 
   public static final class Function extends PType {
-
+    @Serial private static final long serialVersionUID = 0L;
-    private static final long serialVersionUID = 0L;
 
     private final List<PType> parameterTypes;
     private final PType returnType;
@@ -190,8 +185,7 @@ public abstract class PType implements Serializable {
   }
 
   public static final class Union extends PType {
-
+    @Serial private static final long serialVersionUID = 0L;
-    private static final long serialVersionUID = 0L;
 
     private final List<PType> elementTypes;
 
@@ -205,8 +199,7 @@ public abstract class PType implements Serializable {
   }
 
   public static final class TypeVariable extends PType {
-
+    @Serial private static final long serialVersionUID = 0L;
-    private static final long serialVersionUID = 0L;
 
     private final TypeParameter typeParameter;
 

pkl-core/src/main/java/org/pkl/core/Pair.java

@@ -15,13 +15,14 @@
  */
 package org.pkl.core;
 
+import java.io.Serial;
 import java.util.Iterator;
 import java.util.NoSuchElementException;
 import org.pkl.core.util.Nullable;
 
 /** Java representation of a {@code pkl.base#Pair} value. */
 public final class Pair<F, S> implements Value, Iterable<Object> {
-  private static final long serialVersionUID = 0L;
+  @Serial private static final long serialVersionUID = 0L;
 
   private final F first;
   private final S second;
@@ -54,14 +55,11 @@ public final class Pair<F, S> implements Value, Iterable<Object> {
 
       @Override
       public Object next() {
-        switch (pos++) {
+        return switch (pos++) {
-          case 0:
+          case 0 -> first;
-            return first;
+          case 1 -> second;
-          case 1:
+          default -> throw new NoSuchElementException("Pair only has two elements.");
-            return second;
+        };
-          default:
-            throw new NoSuchElementException("Pair only has two elements.");
-        }
       }
     };
   }
@@ -84,9 +82,7 @@ public final class Pair<F, S> implements Value, Iterable<Object> {
   @Override
   public boolean equals(@Nullable Object obj) {
     if (this == obj) return true;
-    if (!(obj instanceof Pair)) return false;
+    if (!(obj instanceof Pair<?, ?> other)) return false;
-
-    var other = (Pair<?, ?>) obj;
     return first.equals(other.first) && second.equals(other.second);
   }
 

pkl-core/src/main/java/org/pkl/core/PcfRenderer.java

@@ -42,14 +42,14 @@ final class PcfRenderer implements ValueRenderer {
 
   @Override
   public void renderDocument(Object value) {
-    if (!(value instanceof Composite)) {
+    if (!(value instanceof Composite composite)) {
       throw new RendererException(
           String.format(
               "The top-level value of a Pcf document must have type `Composite`, but got type `%s`.",
               value.getClass().getTypeName()));
     }
 
-    new Visitor().doVisitProperties(((Composite) value).getProperties());
+    new Visitor().doVisitProperties(composite.getProperties());
   }
 
   @Override

pkl-core/src/main/java/org/pkl/core/Platform.java

@@ -101,9 +101,7 @@ public final class Platform {
   @Override
   public boolean equals(Object obj) {
     if (this == obj) return true;
-    if (!(obj instanceof Platform)) return false;
+    if (!(obj instanceof Platform other)) return false;
-
-    var other = (Platform) obj;
     return language.equals(other.language)
         && runtime.equals(other.runtime)
         && virtualMachine.equals(other.virtualMachine)
@@ -133,9 +131,7 @@ public final class Platform {
     @Override
     public boolean equals(Object obj) {
       if (this == obj) return true;
-      if (!(obj instanceof Language)) return false;
+      if (!(obj instanceof Language other)) return false;
-
-      var other = (Language) obj;
       return version.equals(other.version);
     }
 
@@ -169,9 +165,7 @@ public final class Platform {
     @Override
     public boolean equals(Object obj) {
       if (this == obj) return true;
-      if (!(obj instanceof Runtime)) return false;
+      if (!(obj instanceof Runtime other)) return false;
-
-      var other = (Runtime) obj;
       return name.equals(other.name) && version.equals(other.version);
     }
 
@@ -205,9 +199,7 @@ public final class Platform {
     @Override
     public boolean equals(Object obj) {
       if (this == obj) return true;
-      if (!(obj instanceof VirtualMachine)) return false;
+      if (!(obj instanceof VirtualMachine other)) return false;
-
-      var other = (VirtualMachine) obj;
       return name.equals(other.name) && version.equals(other.version);
     }
 
@@ -241,9 +233,7 @@ public final class Platform {
     @Override
     public boolean equals(Object obj) {
       if (this == obj) return true;
-      if (!(obj instanceof OperatingSystem)) return false;
+      if (!(obj instanceof OperatingSystem other)) return false;
-
-      var other = (OperatingSystem) obj;
       return name.equals(other.name) && version.equals(other.version);
     }
 
@@ -270,9 +260,7 @@ public final class Platform {
     @Override
     public boolean equals(Object obj) {
       if (this == obj) return true;
-      if (!(obj instanceof Processor)) return false;
+      if (!(obj instanceof Processor other)) return false;
-
-      var other = (Processor) obj;
       return architecture.equals(other.architecture);
     }
 

pkl-core/src/main/java/org/pkl/core/PropertiesRenderer.java

@@ -49,12 +49,11 @@ final class PropertiesRenderer implements ValueRenderer {
   private class Visitor implements ValueConverter<String> {
 
     public void renderDocument(Object value) {
-      if (value instanceof Composite) {
+      if (value instanceof Composite composite) {
-        doVisitMap(null, ((Composite) value).getProperties());
+        doVisitMap(null, composite.getProperties());
-      } else if (value instanceof Map) {
+      } else if (value instanceof Map<?, ?> map) {
-        doVisitMap(null, (Map<?, ?>) value);
+        doVisitMap(null, map);
-      } else if (value instanceof Pair) {
+      } else if (value instanceof Pair<?, ?> pair) {
-        Pair<?, ?> pair = (Pair<?, ?>) value;
         doVisitKeyAndValue(null, pair.getFirst(), pair.getSecond());
       } else {
         throw new RendererException(
@@ -181,10 +180,10 @@ final class PropertiesRenderer implements ValueRenderer {
 
       var keyString = keyPrefix == null ? convert(key) : keyPrefix + "." + convert(key);
 
-      if (value instanceof Composite) {
+      if (value instanceof Composite composite) {
-        doVisitMap(keyString, ((Composite) value).getProperties());
+        doVisitMap(keyString, composite.getProperties());
-      } else if (value instanceof Map) {
+      } else if (value instanceof Map<?, ?> map) {
-        doVisitMap(keyString, (Map<?, ?>) value);
+        doVisitMap(keyString, map);
       } else {
         write(keyString, true, restrictCharset);
         writeSeparator();

pkl-core/src/main/java/org/pkl/core/Release.java

@@ -148,9 +148,7 @@ public class Release {
   @Override
   public boolean equals(Object obj) {
     if (this == obj) return true;
-    if (!(obj instanceof Release)) return false;
+    if (!(obj instanceof Release other)) return false;
-
-    var other = (Release) obj;
     return version.equals(other.version)
         && versionInfo.equals(other.versionInfo)
         && commitId.equals(other.commitId)
@@ -200,9 +198,7 @@ public class Release {
     @Override
     public boolean equals(Object obj) {
       if (this == obj) return true;
-      if (!(obj instanceof SourceCode)) return false;
+      if (!(obj instanceof SourceCode other)) return false;
-
-      var other = (SourceCode) obj;
       return homepage.equals(other.homepage) && version.equals(other.version);
     }
 
@@ -229,9 +225,7 @@ public class Release {
     @Override
     public boolean equals(Object obj) {
       if (this == obj) return true;
-      if (!(obj instanceof Documentation)) return false;
+      if (!(obj instanceof Documentation other)) return false;
-
-      var other = (Documentation) obj;
       return homepage.equals(other.homepage);
     }
 
@@ -262,9 +256,7 @@ public class Release {
     @Override
     public boolean equals(Object obj) {
       if (this == obj) return true;
-      if (!(obj instanceof StandardLibrary)) return false;
+      if (!(obj instanceof StandardLibrary other)) return false;
-
-      var other = (StandardLibrary) obj;
       return modules.equals(other.modules);
     }
 

pkl-core/src/main/java/org/pkl/core/SecurityManagers.java

@@ -75,21 +75,16 @@ public final class SecurityManagers {
       SecurityManagers::getDefaultTrustLevel;
 
   private static int getDefaultTrustLevel(URI uri) {
-    switch (uri.getScheme()) {
+    return switch (uri.getScheme()) {
-      case "repl":
+      case "repl" -> 40;
-        return 40;
+      case "file" -> uri.getHost() == null ? 30 : 10;
-      case "file":
+      case "jar" ->
-        return uri.getHost() == null ? 30 : 10;
+          // use trust level of embedded URL
-      case "jar":
+          getDefaultTrustLevel(URI.create(uri.toString().substring(4)));
-        // use trust level of embedded URL
+      case "modulepath" -> 20;
-        return getDefaultTrustLevel(URI.create(uri.toString().substring(4)));
+      case "pkl" -> 0;
-      case "modulepath":
+      default -> 10;
-        return 20;
+    };
-      case "pkl":
-        return 0;
-      default:
-        return 10;
-    }
   }
 
   /**

pkl-core/src/main/java/org/pkl/core/StackFrame.java

@@ -105,10 +105,7 @@ public final class StackFrame {
   @Override
   public boolean equals(@Nullable Object obj) {
     if (this == obj) return true;
-    if (!(obj instanceof StackFrame)) return false;
+    if (!(obj instanceof StackFrame other)) return false;
-
-    var other = (StackFrame) obj;
-
     if (startLine != other.startLine) return false;
     if (startColumn != other.startColumn) return false;
     if (endLine != other.endLine) return false;

pkl-core/src/main/java/org/pkl/core/TypeAlias.java

@@ -15,6 +15,7 @@
  */
 package org.pkl.core;
 
+import java.io.Serial;
 import java.util.List;
 import java.util.Set;
 import org.pkl.core.util.LateInit;
@@ -22,7 +23,7 @@ import org.pkl.core.util.Nullable;
 
 /** Java representation of a {@code pkl.base#TypeAlias} value. */
 public final class TypeAlias extends Member implements Value {
-  private static final long serialVersionUID = 0L;
+  @Serial private static final long serialVersionUID = 0L;
 
   private final String moduleName;
   private final String qualifiedName;

pkl-core/src/main/java/org/pkl/core/TypeParameter.java

@@ -15,13 +15,13 @@
  */
 package org.pkl.core;
 
+import java.io.Serial;
 import java.io.Serializable;
 import org.pkl.core.util.LateInit;
 
 /** A type parameter of a generic class, type alias, or method. */
 public final class TypeParameter implements Serializable {
-
+  @Serial private static final long serialVersionUID = 0L;
-  private static final long serialVersionUID = 0L;
 
   private final Variance variance;
   private final String name;

pkl-core/src/main/java/org/pkl/core/ValueConverter.java

@@ -56,24 +56,24 @@ public interface ValueConverter<T> {
   T convertRegex(Pattern value);
 
   default T convert(Object value) {
-    if (value instanceof Value) {
+    if (value instanceof Value v) {
-      return ((Value) value).accept(this);
+      return (v.accept(this));
-    } else if (value instanceof String) {
+    } else if (value instanceof String string) {
-      return convertString((String) value);
+      return convertString(string);
-    } else if (value instanceof Boolean) {
+    } else if (value instanceof Boolean b) {
-      return convertBoolean((Boolean) value);
+      return convertBoolean(b);
-    } else if (value instanceof Long) {
+    } else if (value instanceof Long l) {
-      return convertInt((Long) value);
+      return convertInt(l);
-    } else if (value instanceof Double) {
+    } else if (value instanceof Double d) {
-      return convertFloat((Double) value);
+      return convertFloat(d);
-    } else if (value instanceof List) {
+    } else if (value instanceof List<?> list) {
-      return convertList((List<?>) value);
+      return convertList(list);
-    } else if (value instanceof Set) {
+    } else if (value instanceof Set<?> set) {
-      return convertSet((Set<?>) value);
+      return convertSet(set);
-    } else if (value instanceof Map) {
+    } else if (value instanceof Map<?, ?> map) {
-      return convertMap((Map<?, ?>) value);
+      return convertMap(map);
-    } else if (value instanceof Pattern) {
+    } else if (value instanceof Pattern pattern) {
-      return convertRegex((Pattern) value);
+      return convertRegex(pattern);
     } else {
       throw new IllegalArgumentException("Cannot convert value with unexpected type: " + value);
     }

pkl-core/src/main/java/org/pkl/core/ValueFormatter.java

@@ -135,31 +135,24 @@ public final class ValueFormatter {
     for (; i < value.length(); i++) {
       var ch = value.charAt(i);
       switch (ch) {
-        case '\n':
+        case '\n' -> appendable.append(escapeSequence).append('n');
-          appendable.append(escapeSequence).append('n');
+        case '\r' -> appendable.append(escapeSequence).append('r');
-          break;
+        case '\t' -> appendable.append(escapeSequence).append('t');
-        case '\r':
+        case '\\' -> {
-          appendable.append(escapeSequence).append('r');
-          break;
-        case '\t':
-          appendable.append(escapeSequence).append('t');
-          break;
-        case '\\':
           if (useCustomStringDelimiters) {
             appendable.append(ch);
           } else {
             appendable.append("\\\\");
           }
-          break;
+        }
-        case '"':
+        case '"' -> {
           if (useCustomStringDelimiters) {
             appendable.append(ch);
           } else {
             appendable.append("\\\"");
           }
-          break;
+        }
-        default:
+        default -> appendable.append(ch);
-          appendable.append(ch);
       }
     }
 
@@ -177,27 +170,27 @@ public final class ValueFormatter {
     for (var i = 0; i < value.length(); i++) {
       var ch = value.charAt(i);
       switch (ch) {
-        case '\n':
+        case '\n' -> {
           appendable.append('\n').append(lineIndent);
           consecutiveQuotes = 0;
-          break;
+        }
-        case '\r':
+        case '\r' -> {
           appendable.append(escapeSequence).append('r');
           consecutiveQuotes = 0;
-          break;
+        }
-        case '\t':
+        case '\t' -> {
           appendable.append(escapeSequence).append('t');
           consecutiveQuotes = 0;
-          break;
+        }
-        case '\\':
+        case '\\' -> {
           if (useCustomStringDelimiters) {
             appendable.append(ch);
           } else {
             appendable.append("\\\\");
           }
           consecutiveQuotes = 0;
-          break;
+        }
-        case '"':
+        case '"' -> {
           if (consecutiveQuotes == 2 && !useCustomStringDelimiters) {
             appendable.append("\\\"");
             consecutiveQuotes = 0;
@@ -205,10 +198,11 @@ public final class ValueFormatter {
             appendable.append('"');
             consecutiveQuotes += 1;
           }
-          break;
+        }
-        default:
+        default -> {
           appendable.append(ch);
           consecutiveQuotes = 0;
+        }
       }
     }
 
@@ -272,12 +266,12 @@ public final class ValueFormatter {
       for (var i = 0; i < value.length(); i++) {
         var ch = value.charAt(i);
         switch (ch) {
-          case '\\':
+          case '\\' -> {
             currentPoundContext = PoundContext.BACKSLASH;
             currentPoundCountBackslash = 1;
             poundCountBackslash = Math.max(poundCountBackslash, currentPoundCountBackslash);
-            break;
+          }
-          case '"':
+          case '"' -> {
             consecutiveQuoteCount += 1;
             if (consecutiveQuoteCount < 3) {
               currentPoundContext = PoundContext.SINGLELINE_QUOTE;
@@ -289,34 +283,36 @@ public final class ValueFormatter {
               poundCountMultilineQuote =
                   Math.max(poundCountMultilineQuote, currentPoundCountMultilineQuote);
             }
-            break;
+          }
-          case '#':
+          case '#' -> {
             consecutiveQuoteCount = 0;
             switch (currentPoundContext) {
-              case SINGLELINE_QUOTE:
+              case SINGLELINE_QUOTE -> {
                 currentPoundCountSingleQuote += 1;
                 poundCountSingleQuote =
                     Math.max(poundCountSingleQuote, currentPoundCountSingleQuote);
-                break;
+              }
-              case MULTILINE_QUOTE:
+              case MULTILINE_QUOTE -> {
                 currentPoundCountMultilineQuote += 1;
                 poundCountMultilineQuote =
                     Math.max(poundCountMultilineQuote, currentPoundCountMultilineQuote);
-                break;
+              }
-              case BACKSLASH:
+              case BACKSLASH -> {
                 currentPoundCountBackslash += 1;
                 poundCountBackslash = Math.max(poundCountBackslash, currentPoundCountBackslash);
-                break;
+              }
-              default:
+              default -> {}
-                break;
             }
-            break;
+          }
-          case '\n':
+          case '\n' -> {
             isMultiline = true;
-          default:
             consecutiveQuoteCount = 0;
             currentPoundContext = PoundContext.OTHER;
-            break;
+          }
+          default -> {
+            consecutiveQuoteCount = 0;
+            currentPoundContext = PoundContext.OTHER;
+          }
         }
       }
       return new StringFacts(

pkl-core/src/main/java/org/pkl/core/ValueVisitor.java

@@ -90,24 +90,24 @@ public interface ValueVisitor {
   }
 
   default void visit(Object value) {
-    if (value instanceof Value) {
+    if (value instanceof Value v) {
-      ((Value) value).accept(this);
+      v.accept(this);
-    } else if (value instanceof String) {
+    } else if (value instanceof String string) {
-      visitString((String) value);
+      visitString(string);
-    } else if (value instanceof Boolean) {
+    } else if (value instanceof Boolean b) {
-      visitBoolean((Boolean) value);
+      visitBoolean(b);
-    } else if (value instanceof Long) {
+    } else if (value instanceof Long l) {
-      visitInt((Long) value);
+      visitInt(l);
-    } else if (value instanceof Double) {
+    } else if (value instanceof Double d) {
-      visitFloat((Double) value);
+      visitFloat(d);
-    } else if (value instanceof List) {
+    } else if (value instanceof List<?> list) {
-      visitList((List<?>) value);
+      visitList(list);
-    } else if (value instanceof Set) {
+    } else if (value instanceof Set<?> set) {
-      visitSet((Set<?>) value);
+      visitSet(set);
-    } else if (value instanceof Map) {
+    } else if (value instanceof Map<?, ?> map) {
-      visitMap((Map<?, ?>) value);
+      visitMap(map);
-    } else if (value instanceof Pattern) {
+    } else if (value instanceof Pattern pattern) {
-      visitRegex((Pattern) value);
+      visitRegex(pattern);
     } else {
       throw new IllegalArgumentException("Cannot visit value with unexpected type: " + value);
     }

pkl-core/src/main/java/org/pkl/core/Version.java

@@ -194,9 +194,7 @@ public final class Version implements Comparable<Version> {
   @Override
   public boolean equals(@Nullable Object obj) {
     if (this == obj) return true;
-    if (!(obj instanceof Version)) return false;
+    if (!(obj instanceof Version other)) return false;
-
-    var other = (Version) obj;
     return major == other.major
         && minor == other.minor
         && patch == other.patch
@@ -210,8 +208,7 @@ public final class Version implements Comparable<Version> {
 
   @Override
   public String toString() {
-    return ""
+    return major
-        + major
         + "."
         + minor
         + "."

pkl-core/src/main/java/org/pkl/core/YamlRenderer.java

@@ -75,13 +75,12 @@ final class YamlRenderer implements ValueRenderer {
   @Override
   public void renderDocument(Object value) {
     if (isStream) {
-      if (!(value instanceof Iterable)) {
+      if (!(value instanceof Iterable<?> iterable)) {
         throw new RendererException(
             String.format(
                 "The top-level value of a YAML stream must have type `Collection`, but got type `%s`.",
                 value.getClass().getTypeName()));
       }
-      var iterable = (Iterable<?>) value;
       emitter.emit(new StreamStartEvent());
       for (var elem : iterable) {
         emitter.emit(new DocumentStartEvent(false, Optional.empty(), Map.of()));

pkl-core/src/main/java/org/pkl/core/ast/MemberNode.java

@@ -89,7 +89,6 @@ public abstract class MemberNode extends PklRootNode {
   }
 
   public boolean isUndefined() {
-    return bodyNode instanceof DefaultPropertyBodyNode
+    return bodyNode instanceof DefaultPropertyBodyNode propBodyNode && propBodyNode.isUndefined();
-        && ((DefaultPropertyBodyNode) bodyNode).isUndefined();
   }
 }

pkl-core/src/main/java/org/pkl/core/ast/VmModifier.java

@@ -161,26 +161,19 @@ public final class VmModifier {
   }
 
   public static String toString(int modifier) {
-    switch (modifier) {
+    return switch (modifier) {
-      case ABSTRACT:
+      case ABSTRACT -> "abstract";
-        return "abstract";
+      case OPEN -> "open";
-      case OPEN:
+      case LOCAL -> "local";
-        return "open";
+      case HIDDEN -> "hidden";
-      case LOCAL:
+      case EXTERNAL -> "external";
-        return "local";
+      case FIXED -> "fixed";
-      case HIDDEN:
+      case CONST -> "const";
-        return "hidden";
+      default ->
-      case EXTERNAL:
+          throw new VmExceptionBuilder()
-        return "external";
+              .bug("Cannot convert internal modifier `%s` to a string.", toString(modifier))
-      case FIXED:
+              .build();
-        return "fixed";
+    };
-      case CONST:
-        return "const";
-      default:
-        throw new VmExceptionBuilder()
-            .bug("Cannot convert internal modifier `%s` to a string.", toString(modifier))
-            .build();
-    }
   }
 
   public static VmSet getMirrors(int modifiers, boolean isClass) {

pkl-core/src/main/java/org/pkl/core/ast/builder/AbstractAstBuilder.java

@@ -43,17 +43,10 @@ public abstract class AbstractAstBuilder<T> extends PklParserBaseVisitor<T> {
     var builder = new StringBuilder();
     for (var token : ts) {
       switch (token.getType()) {
-        case PklLexer.SLCharacters:
+        case PklLexer.SLCharacters -> builder.append(token.getText());
-          builder.append(token.getText());
+        case PklLexer.SLCharacterEscape -> builder.append(parseCharacterEscapeSequence(token));
-          break;
+        case PklLexer.SLUnicodeEscape -> builder.appendCodePoint(parseUnicodeEscapeSequence(token));
-        case PklLexer.SLCharacterEscape:
+        default -> throw exceptionBuilder().unreachableCode().build();
-          builder.append(parseCharacterEscapeSequence(token));
-          break;
-        case PklLexer.SLUnicodeEscape:
-          builder.appendCodePoint(parseUnicodeEscapeSequence(token));
-          break;
-        default:
-          throw exceptionBuilder().unreachableCode().build();
       }
     }
 
@@ -88,23 +81,19 @@ public abstract class AbstractAstBuilder<T> extends PklParserBaseVisitor<T> {
     var text = token.getText();
     var lastChar = text.charAt(text.length() - 1);
 
-    switch (lastChar) {
+    return switch (lastChar) {
-      case 'n':
+      case 'n' -> "\n";
-        return "\n";
+      case 'r' -> "\r";
-      case 'r':
+      case 't' -> "\t";
-        return "\r";
+      case '"' -> "\"";
-      case 't':
+      case '\\' -> "\\";
-        return "\t";
+      default ->
-      case '"':
+          throw exceptionBuilder()
-        return "\"";
+              .evalError(
-      case '\\':
+                  "invalidCharacterEscapeSequence", text, text.substring(0, text.length() - 1))
-        return "\\";
+              .withSourceSection(createSourceSection(token))
-      default:
+              .build();
-        throw exceptionBuilder()
+    };
-            .evalError("invalidCharacterEscapeSequence", text, text.substring(0, text.length() - 1))
-            .withSourceSection(createSourceSection(token))
-            .build();
-    }
   }
 
   protected final SourceSection createSourceSection(ParserRuleContext ctx) {

pkl-core/src/main/java/org/pkl/core/ast/builder/AstBuilder.java

@@ -461,7 +461,7 @@ public final class AstBuilder extends AbstractAstBuilder<Object> {
 
     while (parent instanceof IfExprContext
         || parent instanceof TraceExprContext
-        || parent instanceof LetExprContext && ((LetExprContext) parent).r == child) {
+        || parent instanceof LetExprContext letExpr && letExpr.r == child) {
 
       if (parent instanceof LetExprContext) {
         assert scope != null;
@@ -481,7 +481,7 @@ public final class AstBuilder extends AbstractAstBuilder<Object> {
               scope.getName(),
               levelsUp == 0 ? new GetOwnerNode() : new GetEnclosingOwnerNode(levelsUp));
     } else if (parent instanceof ObjectElementContext
-        || parent instanceof ObjectEntryContext && ((ObjectEntryContext) parent).v == child) {
+        || parent instanceof ObjectEntryContext objectEntry && objectEntry.v == child) {
       inferredParentNode =
           ApplyVmFunction1NodeGen.create(
               ReadPropertyNodeGen.create(
@@ -506,7 +506,7 @@ public final class AstBuilder extends AbstractAstBuilder<Object> {
                   language,
                   scopeName,
                   levelsUp == 0 ? new GetOwnerNode() : new GetEnclosingOwnerNode(levelsUp));
-    } else if (parent instanceof LetExprContext && ((LetExprContext) parent).l == child) {
+    } else if (parent instanceof LetExprContext letExpr && letExpr.l == child) {
       // TODO (unclear how to infer type now that let-expression is implemented as lambda
       // invocation)
       throw exceptionBuilder()
@@ -604,8 +604,8 @@ public final class AstBuilder extends AbstractAstBuilder<Object> {
             if (VmModifier.isExternal(modifiers)) {
               bodyNode =
                   externalMemberRegistry.getPropertyBody(scope.getQualifiedName(), headerSection);
-              if (bodyNode instanceof LanguageAwareNode) {
+              if (bodyNode instanceof LanguageAwareNode languageAwareNode) {
-                ((LanguageAwareNode) bodyNode).initLanguage(language);
+                languageAwareNode.initLanguage(language);
               }
             } else if (VmModifier.isAbstract(modifiers)) {
               bodyNode =
@@ -1046,15 +1046,12 @@ public final class AstBuilder extends AbstractAstBuilder<Object> {
 
           checkSpaceSeparatedObjectMembers(ctx);
           for (var memberCtx : objectMemberCtx) {
-            if (memberCtx instanceof ObjectPropertyContext) {
+            if (memberCtx instanceof ObjectPropertyContext propertyCtx) {
-              var propertyCtx = (ObjectPropertyContext) memberCtx;
               addProperty(members, doVisitObjectProperty(propertyCtx));
               continue;
             }
 
-            if (memberCtx instanceof ObjectEntryContext) {
+            if (memberCtx instanceof ObjectEntryContext entryCtx) {
-              var entryCtx = (ObjectEntryContext) memberCtx;
-
               var keyAndValue = doVisitObjectEntry(entryCtx);
               var key = keyAndValue.first;
               keyNodes.add(key);
@@ -1063,15 +1060,13 @@ public final class AstBuilder extends AbstractAstBuilder<Object> {
               continue;
             }
 
-            if (memberCtx instanceof ObjectElementContext) {
+            if (memberCtx instanceof ObjectElementContext elementCtx) {
-              var elementCtx = (ObjectElementContext) memberCtx;
               var element = doVisitObjectElement(elementCtx);
               elements.add(element);
               continue;
             }
 
-            if (memberCtx instanceof ObjectMethodContext) {
+            if (memberCtx instanceof ObjectMethodContext methodCtx) {
-              var methodCtx = (ObjectMethodContext) memberCtx;
               addProperty(members, doVisitObjectMethod(methodCtx));
               continue;
             }
@@ -1191,8 +1186,8 @@ public final class AstBuilder extends AbstractAstBuilder<Object> {
                   null,
                   scope.getQualifiedName());
 
-          if (elementNode instanceof ConstantNode) {
+          if (elementNode instanceof ConstantNode constantNode) {
-            member.initConstantValue((ConstantNode) elementNode);
+            member.initConstantValue(constantNode);
           } else {
             member.initMemberNode(
                 new UntypedObjectMemberNode(
@@ -1248,8 +1243,8 @@ public final class AstBuilder extends AbstractAstBuilder<Object> {
 
       if (valueCtx != null) { // ["key"] = value
         var valueNode = visitExpr(valueCtx);
-        if (valueNode instanceof ConstantNode) {
+        if (valueNode instanceof ConstantNode constantNode) {
-          member.initConstantValue((ConstantNode) valueNode);
+          member.initConstantValue(constantNode);
         } else {
           member.initMemberNode(
               new UntypedObjectMemberNode(
@@ -1297,24 +1292,16 @@ public final class AstBuilder extends AbstractAstBuilder<Object> {
 
   @Override
   public Integer visitModifier(ModifierContext ctx) {
-    switch (ctx.t.getType()) {
+    return switch (ctx.t.getType()) {
-      case PklLexer.EXTERNAL:
+      case PklLexer.EXTERNAL -> VmModifier.EXTERNAL;
-        return VmModifier.EXTERNAL;
+      case PklLexer.ABSTRACT -> VmModifier.ABSTRACT;
-      case PklLexer.ABSTRACT:
+      case PklLexer.OPEN -> VmModifier.OPEN;
-        return VmModifier.ABSTRACT;
+      case PklLexer.LOCAL -> VmModifier.LOCAL;
-      case PklLexer.OPEN:
+      case PklLexer.HIDDEN_ -> VmModifier.HIDDEN;
-        return VmModifier.OPEN;
+      case PklLexer.FIXED -> VmModifier.FIXED;
-      case PklLexer.LOCAL:
+      case PklLexer.CONST -> VmModifier.CONST;
-        return VmModifier.LOCAL;
+      default -> throw createUnexpectedTokenError(ctx.t);
-      case PklLexer.HIDDEN_:
+    };
-        return VmModifier.HIDDEN;
-      case PklLexer.FIXED:
-        return VmModifier.FIXED;
-      case PklLexer.CONST:
-        return VmModifier.CONST;
-      default:
-        throw createUnexpectedTokenError(ctx.t);
-    }
   }
 
   private int doVisitModifiers(
@@ -1410,8 +1397,8 @@ public final class AstBuilder extends AbstractAstBuilder<Object> {
               bodyNode =
                   externalMemberRegistry.getFunctionBody(
                       scope.getQualifiedName(), headerSection, paramCount);
-              if (bodyNode instanceof LanguageAwareNode) {
+              if (bodyNode instanceof LanguageAwareNode languageAwareNode) {
-                ((LanguageAwareNode) bodyNode).initLanguage(language);
+                languageAwareNode.initLanguage(language);
               }
             } else if (VmModifier.isAbstract(modifiers)) {
               bodyNode =
@@ -1730,33 +1717,30 @@ public final class AstBuilder extends AbstractAstBuilder<Object> {
 
   @Override
   public Object visitComparisonExpr(ComparisonExprContext ctx) {
-    switch (ctx.t.getType()) {
+    return switch (ctx.t.getType()) {
-      case PklLexer.LT:
+      case PklLexer.LT ->
-        return LessThanNodeGen.create(createSourceSection(ctx), visitExpr(ctx.l), visitExpr(ctx.r));
+          LessThanNodeGen.create(createSourceSection(ctx), visitExpr(ctx.l), visitExpr(ctx.r));
-      case PklLexer.GT:
+      case PklLexer.GT ->
-        return GreaterThanNodeGen.create(
+          GreaterThanNodeGen.create(createSourceSection(ctx), visitExpr(ctx.l), visitExpr(ctx.r));
-            createSourceSection(ctx), visitExpr(ctx.l), visitExpr(ctx.r));
+      case PklLexer.LTE ->
-      case PklLexer.LTE:
+          LessThanOrEqualNodeGen.create(
-        return LessThanOrEqualNodeGen.create(
+              createSourceSection(ctx), visitExpr(ctx.l), visitExpr(ctx.r));
-            createSourceSection(ctx), visitExpr(ctx.l), visitExpr(ctx.r));
+      case PklLexer.GTE ->
-      case PklLexer.GTE:
+          GreaterThanOrEqualNodeGen.create(
-        return GreaterThanOrEqualNodeGen.create(
+              createSourceSection(ctx), visitExpr(ctx.l), visitExpr(ctx.r));
-            createSourceSection(ctx), visitExpr(ctx.l), visitExpr(ctx.r));
+      default -> throw createUnexpectedTokenError(ctx.t);
-      default:
+    };
-        throw createUnexpectedTokenError(ctx.t);
-    }
   }
 
   @Override
   public Object visitEqualityExpr(EqualityExprContext ctx) {
-    switch (ctx.t.getType()) {
+    return switch (ctx.t.getType()) {
-      case PklLexer.EQUAL:
+      case PklLexer.EQUAL ->
-        return EqualNodeGen.create(createSourceSection(ctx), visitExpr(ctx.l), visitExpr(ctx.r));
+          EqualNodeGen.create(createSourceSection(ctx), visitExpr(ctx.l), visitExpr(ctx.r));
-      case PklLexer.NOT_EQUAL:
+      case PklLexer.NOT_EQUAL ->
-        return NotEqualNodeGen.create(createSourceSection(ctx), visitExpr(ctx.l), visitExpr(ctx.r));
+          NotEqualNodeGen.create(createSourceSection(ctx), visitExpr(ctx.l), visitExpr(ctx.r));
-      default:
+      default -> throw createUnexpectedTokenError(ctx.t);
-        throw createUnexpectedTokenError(ctx.t);
+    };
-    }
   }
 
   @Override
@@ -1879,34 +1863,30 @@ public final class AstBuilder extends AbstractAstBuilder<Object> {
 
   @Override
   public ExpressionNode visitAdditiveExpr(AdditiveExprContext ctx) {
-    switch (ctx.t.getType()) {
+    return switch (ctx.t.getType()) {
-      case PklLexer.PLUS:
+      case PklLexer.PLUS ->
-        return AdditionNodeGen.create(createSourceSection(ctx), visitExpr(ctx.l), visitExpr(ctx.r));
+          AdditionNodeGen.create(createSourceSection(ctx), visitExpr(ctx.l), visitExpr(ctx.r));
-      case PklLexer.MINUS:
+      case PklLexer.MINUS ->
-        return SubtractionNodeGen.create(
+          SubtractionNodeGen.create(createSourceSection(ctx), visitExpr(ctx.l), visitExpr(ctx.r));
-            createSourceSection(ctx), visitExpr(ctx.l), visitExpr(ctx.r));
+      default -> throw createUnexpectedTokenError(ctx.t);
-      default:
+    };
-        throw createUnexpectedTokenError(ctx.t);
-    }
   }
 
   @Override
   public ExpressionNode visitMultiplicativeExpr(MultiplicativeExprContext ctx) {
-    switch (ctx.t.getType()) {
+    return switch (ctx.t.getType()) {
-      case PklLexer.STAR:
+      case PklLexer.STAR ->
-        return MultiplicationNodeGen.create(
+          MultiplicationNodeGen.create(
-            createSourceSection(ctx), visitExpr(ctx.l), visitExpr(ctx.r));
+              createSourceSection(ctx), visitExpr(ctx.l), visitExpr(ctx.r));
-      case PklLexer.DIV:
+      case PklLexer.DIV ->
-        return DivisionNodeGen.create(createSourceSection(ctx), visitExpr(ctx.l), visitExpr(ctx.r));
+          DivisionNodeGen.create(createSourceSection(ctx), visitExpr(ctx.l), visitExpr(ctx.r));
-      case PklLexer.INT_DIV:
+      case PklLexer.INT_DIV ->
-        return TruncatingDivisionNodeGen.create(
+          TruncatingDivisionNodeGen.create(
-            createSourceSection(ctx), visitExpr(ctx.l), visitExpr(ctx.r));
+              createSourceSection(ctx), visitExpr(ctx.l), visitExpr(ctx.r));
-      case PklLexer.MOD:
+      case PklLexer.MOD ->
-        return RemainderNodeGen.create(
+          RemainderNodeGen.create(createSourceSection(ctx), visitExpr(ctx.l), visitExpr(ctx.r));
-            createSourceSection(ctx), visitExpr(ctx.l), visitExpr(ctx.r));
+      default -> throw createUnexpectedTokenError(ctx.t);
-      default:
+    };
-        throw createUnexpectedTokenError(ctx.t);
-    }
   }
 
   @Override
@@ -1951,14 +1931,12 @@ public final class AstBuilder extends AbstractAstBuilder<Object> {
     if (receiver instanceof OuterNode) {
       var outerScope = getParentLexicalScope();
       if (outerScope != null) {
-        switch (constLevel) {
+        needsConst =
-          case MODULE:
+            switch (constLevel) {
-            needsConst = outerScope.isModuleScope();
+              case MODULE -> outerScope.isModuleScope();
-            break;
+              case ALL -> outerScope.getConstLevel() != ConstLevel.ALL;
-          case ALL:
+              case NONE -> false;
-            needsConst = outerScope.getConstLevel() != ConstLevel.ALL;
+            };
-            break;
-        }
       }
     } else if (receiver instanceof GetModuleNode) {
       needsConst = constLevel != ConstLevel.NONE;
@@ -1998,13 +1976,12 @@ public final class AstBuilder extends AbstractAstBuilder<Object> {
     var propertyName = toIdentifier(ctx.Identifier());
     var receiver = visitExpr(ctx.expr());
 
-    if (receiver instanceof IntLiteralNode) {
+    if (receiver instanceof IntLiteralNode intLiteralNode) {
       var durationUnit = VmDuration.toUnit(propertyName);
       if (durationUnit != null) {
         //noinspection ConstantConditions
         return new ConstantValueNode(
-            sourceSection,
+            sourceSection, new VmDuration(intLiteralNode.executeInt(null), durationUnit));
-            new VmDuration(((IntLiteralNode) receiver).executeInt(null), durationUnit));
       }
       var dataSizeUnit = VmDataSize.toUnit(propertyName);
       if (dataSizeUnit != null) {
@@ -2015,13 +1992,12 @@ public final class AstBuilder extends AbstractAstBuilder<Object> {
       }
     }
 
-    if (receiver instanceof FloatLiteralNode) {
+    if (receiver instanceof FloatLiteralNode floatLiteralNode) {
       var durationUnit = VmDuration.toUnit(propertyName);
       if (durationUnit != null) {
         //noinspection ConstantConditions
         return new ConstantValueNode(
-            sourceSection,
+            sourceSection, new VmDuration(floatLiteralNode.executeFloat(null), durationUnit));
-            new VmDuration(((FloatLiteralNode) receiver).executeFloat(null), durationUnit));
       }
       var dataSizeUnit = VmDataSize.toUnit(propertyName);
       if (dataSizeUnit != null) {
@@ -2037,14 +2013,12 @@ public final class AstBuilder extends AbstractAstBuilder<Object> {
     if (receiver instanceof OuterNode) {
       var outerScope = getParentLexicalScope();
       if (outerScope != null) {
-        switch (constLevel) {
+        needsConst =
-          case MODULE:
+            switch (constLevel) {
-            needsConst = outerScope.isModuleScope();
+              case MODULE -> outerScope.isModuleScope();
-            break;
+              case ALL -> outerScope.getConstLevel() != ConstLevel.ALL;
-          case ALL:
+              case NONE -> false;
-            needsConst = outerScope.getConstLevel() != ConstLevel.ALL;
+            };
-            break;
-        }
       }
     } else if (receiver instanceof GetModuleNode) {
       needsConst = constLevel != ConstLevel.NONE;
@@ -2482,13 +2456,12 @@ public final class AstBuilder extends AbstractAstBuilder<Object> {
 
     while (!list.isEmpty()) {
       var current = list.removeFirst();
-      if (current instanceof UnionTypeContext) {
+      if (current instanceof UnionTypeContext unionType) {
-        var union = (UnionTypeContext) current;
+        list.addFirst(unionType.r);
-        list.addFirst(union.r);
+        list.addFirst(unionType.l);
-        list.addFirst(union.l);
         continue;
       }
-      if (current instanceof DefaultUnionTypeContext) {
+      if (current instanceof DefaultUnionTypeContext defaultUnionType) {
         if (defaultIndex == -1) {
           defaultIndex = index;
         } else {
@@ -2497,10 +2470,9 @@ public final class AstBuilder extends AbstractAstBuilder<Object> {
               .withSourceSection(createSourceSection(ctx))
               .build();
         }
-        var def = (DefaultUnionTypeContext) current;
         isUnionOfStringLiterals =
-            isUnionOfStringLiterals && def.type() instanceof StringLiteralTypeContext;
+            isUnionOfStringLiterals && defaultUnionType.type() instanceof StringLiteralTypeContext;
-        collector.add(def.type());
+        collector.add(defaultUnionType.type());
       } else {
         isUnionOfStringLiterals =
             isUnionOfStringLiterals && current instanceof StringLiteralTypeContext;
@@ -2735,7 +2707,7 @@ public final class AstBuilder extends AbstractAstBuilder<Object> {
     }
 
     var tokens = lastPart.ts;
-    assert tokens.size() >= 1;
+    assert !tokens.isEmpty();
     var lastToken = tokens.get(tokens.size() - 1);
 
     if (lastToken.getType() == PklLexer.MLNewline) {
@@ -2759,13 +2731,8 @@ public final class AstBuilder extends AbstractAstBuilder<Object> {
     var text = token.getText();
 
     for (var i = 0; i < text.length(); i++) {
-      switch (text.charAt(i)) {
+      var ch = text.charAt(i);
-        case ' ':
+      if (ch != ' ' && ch != '\t') return false;
-        case '\t':
-          continue;
-        default:
-          return false;
-      }
     }
 
     return true;
@@ -2775,12 +2742,9 @@ public final class AstBuilder extends AbstractAstBuilder<Object> {
     var text = token.getText();
 
     for (var i = 0; i < text.length(); i++) {
-      switch (text.charAt(i)) {
+      var ch = text.charAt(i);
-        case ' ':
+      if (ch != ' ' && ch != '\t') {
-        case '\t':
+        return text.substring(0, i);
-          continue;
-        default:
-          return text.substring(0, i);
       }
     }
 
@@ -2829,11 +2793,11 @@ public final class AstBuilder extends AbstractAstBuilder<Object> {
       Token token = tokens.get(i);
 
       switch (token.getType()) {
-        case PklLexer.MLNewline:
+        case PklLexer.MLNewline -> {
           builder.append('\n');
           isLineStart = true;
-          break;
+        }
-        case PklLexer.MLCharacters:
+        case PklLexer.MLCharacters -> {
           var text = token.getText();
           if (isLineStart) {
             if (text.startsWith(commonIndent)) {
@@ -2852,8 +2816,8 @@ public final class AstBuilder extends AbstractAstBuilder<Object> {
             builder.append(text);
           }
           isLineStart = false;
-          break;
+        }
-        case PklLexer.MLCharacterEscape:
+        case PklLexer.MLCharacterEscape -> {
           if (isLineStart && !commonIndent.isEmpty()) {
             throw exceptionBuilder()
                 .evalError("stringIndentationMustMatchLastLine")
@@ -2862,8 +2826,8 @@ public final class AstBuilder extends AbstractAstBuilder<Object> {
           }
           builder.append(parseCharacterEscapeSequence(token));
           isLineStart = false;
-          break;
+        }
-        case PklLexer.MLUnicodeEscape:
+        case PklLexer.MLUnicodeEscape -> {
           if (isLineStart && !commonIndent.isEmpty()) {
             throw exceptionBuilder()
                 .evalError("stringIndentationMustMatchLastLine")
@@ -2872,9 +2836,8 @@ public final class AstBuilder extends AbstractAstBuilder<Object> {
           }
           builder.appendCodePoint(parseUnicodeEscapeSequence(token));
           isLineStart = false;
-          break;
+        }
-        default:
+        default -> throw exceptionBuilder().unreachableCode().build();
-          throw exceptionBuilder().unreachableCode().build();
       }
     }
 
@@ -2883,26 +2846,28 @@ public final class AstBuilder extends AbstractAstBuilder<Object> {
 
   private ResolveDeclaredTypeNode doVisitTypeName(QualifiedIdentifierContext ctx) {
     var tokens = ctx.ts;
-    switch (tokens.size()) {
+    return switch (tokens.size()) {
-      case 1:
+      case 1 -> {
         var token = tokens.get(0);
-        return new ResolveSimpleDeclaredTypeNode(
+        yield new ResolveSimpleDeclaredTypeNode(
             createSourceSection(token), Identifier.get(token.getText()), isBaseModule);
-      case 2:
+      }
+      case 2 -> {
         var token1 = tokens.get(0);
         var token2 = tokens.get(1);
-        return new ResolveQualifiedDeclaredTypeNode(
+        yield new ResolveQualifiedDeclaredTypeNode(
             createSourceSection(ctx),
             createSourceSection(token1),
             createSourceSection(token2),
             Identifier.localProperty(token1.getText()),
             Identifier.get(token2.getText()));
-      default:
+      }
-        throw exceptionBuilder()
+      default ->
-            .evalError("invalidTypeName", ctx.getText())
+          throw exceptionBuilder()
-            .withSourceSection(createSourceSection(ctx))
+              .evalError("invalidTypeName", ctx.getText())
-            .build();
+              .withSourceSection(createSourceSection(ctx))
-    }
+              .build();
+    };
   }
 
   private void checkCommaSeparatedElements(
@@ -2918,11 +2883,11 @@ public final class AstBuilder extends AbstractAstBuilder<Object> {
       var index = elements.indexOf(child);
       if (index > 0) { // 0 rather than -1 because no separator is expected before first element
         assert prevChild != null;
-        if (!(prevChild instanceof TerminalNode)
+        if (!(prevChild instanceof TerminalNode terminalNode)
-            || !separators.contains(((TerminalNode) prevChild).getSymbol())) {
+            || !separators.contains(terminalNode.getSymbol())) {
           var prevToken =
-              prevChild instanceof TerminalNode
+              prevChild instanceof TerminalNode terminalNode
-                  ? ((TerminalNode) prevChild).getSymbol()
+                  ? terminalNode.getSymbol()
                   : ((ParserRuleContext) prevChild).getStop();
           throw exceptionBuilder()
               .evalError("missingCommaSeparator")

pkl-core/src/main/java/org/pkl/core/ast/builder/ImportsAndReadsParser.java

@@ -93,11 +93,10 @@ public class ImportsAndReadsParser
   @Override
   public List<Pair<String, SourceSection>> visitReadExpr(ReadExprContext ctx) {
     var expr = ctx.expr();
-    if (!(expr instanceof SingleLineStringLiteralContext)) {
+    if (!(expr instanceof SingleLineStringLiteralContext slCtx)) {
       return Collections.emptyList();
     }
     // best-effort approach; only collect read expressions that are string constants.
-    var slCtx = (SingleLineStringLiteralContext) expr;
     var singleParts = slCtx.singleLineStringPart();
     String importString;
     if (singleParts.isEmpty()) {

pkl-core/src/main/java/org/pkl/core/ast/builder/SymbolTable.java

@@ -284,8 +284,8 @@ public final class SymbolTable {
     }
 
     private String getNextEntryName(@Nullable ExpressionNode keyNode) {
-      if (keyNode instanceof ConstantNode) {
+      if (keyNode instanceof ConstantNode constantNode) {
-        var value = ((ConstantNode) keyNode).getValue();
+        var value = constantNode.getValue();
         if (value instanceof String) {
           return "[\"" + value + "\"]";
         }

pkl-core/src/main/java/org/pkl/core/ast/expression/binary/EqualNode.java

@@ -90,7 +90,7 @@ public abstract class EqualNode extends ExpressionNode {
 
   protected static @Nullable Class<? extends VmValue> getVmValueJavaClassOrNull(Object value) {
     // OK to perform slow cast here (not a guard)
-    return value instanceof VmValue ? ((VmValue) value).getClass() : null;
+    return value instanceof VmValue vmValue ? vmValue.getClass() : null;
   }
 
   // covers all remaining cases (else it's a bug)

pkl-core/src/main/java/org/pkl/core/ast/expression/binary/NotEqualNode.java

@@ -90,7 +90,7 @@ public abstract class NotEqualNode extends ExpressionNode {
 
   protected static @Nullable Class<? extends VmValue> getVmValueJavaClassOrNull(Object value) {
     // OK to perform slow cast here (not a guard)
-    return value instanceof VmValue ? ((VmValue) value).getClass() : null;
+    return value instanceof VmValue vmValue ? vmValue.getClass() : null;
   }
 
   // covers all remaining cases (else it's a bug)

pkl-core/src/main/java/org/pkl/core/ast/expression/generator/GeneratorObjectLiteralNode.java

@@ -161,7 +161,7 @@ public abstract class GeneratorObjectLiteralNode extends ObjectLiteralNode {
   @TruffleBoundary
   protected void fallback(Object parent) {
     VmUtils.checkIsInstantiable(
-        parent instanceof VmClass ? (VmClass) parent : VmUtils.getClass(parent), getParentNode());
+        parent instanceof VmClass vmClass ? vmClass : VmUtils.getClass(parent), getParentNode());
 
     throw exceptionBuilder().unreachableCode().build();
   }

pkl-core/src/main/java/org/pkl/core/ast/expression/generator/GeneratorSpreadNode.java

@@ -167,7 +167,7 @@ public abstract class GeneratorSpreadNode extends GeneratorMemberNode {
             .evalError("cannotIterateOverThisValue", VmUtils.getClass(iterable))
             .withLocation(iterableNode)
             .withProgramValue("Value", iterable);
-    if (iterable instanceof VmObject && ((VmObject) iterable).isTyped()) {
+    if (iterable instanceof VmObject vmObject && vmObject.isTyped()) {
       builder.withHint(
           "`Typed` values are not iterable. If you mean to spread its members, convert it to `Dynamic` using `toDynamic()`.");
     }

pkl-core/src/main/java/org/pkl/core/ast/expression/literal/AmendFunctionNode.java

@@ -187,7 +187,7 @@ public final class AmendFunctionNode extends PklNode {
       System.arraycopy(frameArguments, 2, arguments, 2, frameArguments.length - 2);
 
       var valueToAmend = callNode.call(functionToAmend.getCallTarget(), arguments);
-      if (!(valueToAmend instanceof VmFunction)) {
+      if (!(valueToAmend instanceof VmFunction newFunctionToAmend)) {
         var materializedFrame = context.frame;
         if (materializedFrame != null) {
           for (var slot : parameterSlots) {
@@ -199,7 +199,6 @@ public final class AmendFunctionNode extends PklNode {
         return amendObjectNode.executeGeneric(frame);
       }
 
-      var newFunctionToAmend = (VmFunction) valueToAmend;
       return currentFunction.copy(
           newFunctionToAmend.getParameterCount(),
           nextFunctionRootNode,

pkl-core/src/main/java/org/pkl/core/ast/expression/literal/SpecializedObjectLiteralNode.java

@@ -70,7 +70,7 @@ public abstract class SpecializedObjectLiteralNode extends ObjectLiteralNode {
   @TruffleBoundary
   @Idempotent
   protected boolean checkIsValidTypedAmendment(Object parent) {
-    var parentClass = parent instanceof VmClass ? (VmClass) parent : VmUtils.getClass(parent);
+    var parentClass = parent instanceof VmClass vmClass ? vmClass : VmUtils.getClass(parent);
     VmUtils.checkIsInstantiable(parentClass, getParentNode());
 
     for (var member : EconomicMaps.getValues(members)) {

pkl-core/src/main/java/org/pkl/core/ast/expression/member/ReadPropertyNode.java

@@ -92,7 +92,7 @@ public abstract class ReadPropertyNode extends ExpressionNode {
 
   protected static @Nullable Class<? extends VmObjectLike> getVmObjectSubclassOrNull(Object value) {
     // OK to perform slow cast here (not a guard)
-    return value instanceof VmObjectLike ? ((VmObjectLike) value).getClass() : null;
+    return value instanceof VmObjectLike objectLike ? objectLike.getClass() : null;
   }
 
   protected ClassProperty resolveProperty(Object value) {

pkl-core/src/main/java/org/pkl/core/ast/expression/member/ResolveMethodNode.java

@@ -168,15 +168,12 @@ public final class ResolveMethodNode extends ExpressionNode {
       return;
     }
     var memberIsOutsideConstScope = levelsUp > constDepth;
-    var invalid = false;
+    var invalid =
-    switch (constLevel) {
+        switch (constLevel) {
-      case ALL:
+          case ALL -> memberIsOutsideConstScope && !method.isConst();
-        invalid = memberIsOutsideConstScope && !method.isConst();
+          case MODULE -> currOwner.isModuleObject() && !method.isConst();
-        break;
+          default -> false;
-      case MODULE:
+        };
-        invalid = currOwner.isModuleObject() && !method.isConst();
-        break;
-    }
     if (invalid) {
       throw exceptionBuilder().evalError("methodMustBeConst", methodName.toString()).build();
     }

pkl-core/src/main/java/org/pkl/core/ast/expression/primary/ResolveVariableNode.java

@@ -226,15 +226,12 @@ public final class ResolveVariableNode extends ExpressionNode {
       return;
     }
     var memberIsOutsideConstScope = levelsUp > constDepth;
-    var invalid = false;
+    var invalid =
-    switch (constLevel) {
+        switch (constLevel) {
-      case ALL:
+          case ALL -> memberIsOutsideConstScope && !member.isConst();
-        invalid = memberIsOutsideConstScope && !member.isConst();
+          case MODULE -> currOwner.isModuleObject() && !member.isConst();
-        break;
+          default -> false;
-      case MODULE:
+        };
-        invalid = currOwner.isModuleObject() && !member.isConst();
-        break;
-    }
     if (invalid) {
       throw exceptionBuilder().evalError("propertyMustBeConst", variableName.toString()).build();
     }

pkl-core/src/main/java/org/pkl/core/ast/expression/unary/TraceNode.java

@@ -40,9 +40,9 @@ public final class TraceNode extends ExpressionNode {
 
   @TruffleBoundary
   private void doTrace(Object value, VmContext context) {
-    if (value instanceof VmObjectLike) {
+    if (value instanceof VmObjectLike objectLike) {
       try {
-        ((VmObjectLike) value).force(true, true);
+        objectLike.force(true, true);
       } catch (VmException ignored) {
       }
     }

pkl-core/src/main/java/org/pkl/core/ast/lambda/ApplyVmFunction1Node.java

@@ -39,7 +39,7 @@ public abstract class ApplyVmFunction1Node extends ExpressionNode {
 
   public final boolean executeBoolean(VmFunction function, Object arg1) {
     var result = execute(function, arg1);
-    if (result instanceof Boolean) return (Boolean) result;
+    if (result instanceof Boolean b) return b;
 
     CompilerDirectives.transferToInterpreter();
     throw exceptionBuilder().typeMismatch(result, BaseModule.getBooleanClass()).build();
@@ -47,7 +47,7 @@ public abstract class ApplyVmFunction1Node extends ExpressionNode {
 
   public final String executeString(VmFunction function, Object arg1) {
     var result = execute(function, arg1);
-    if (result instanceof String) return (String) result;
+    if (result instanceof String string) return string;
 
     CompilerDirectives.transferToInterpreter();
     throw exceptionBuilder().typeMismatch(result, BaseModule.getStringClass()).build();
@@ -55,7 +55,7 @@ public abstract class ApplyVmFunction1Node extends ExpressionNode {
 
   public final Long executeInt(VmFunction function, Object arg1) {
     var result = execute(function, arg1);
-    if (result instanceof Long) return (Long) result;
+    if (result instanceof Long l) return l;
 
     CompilerDirectives.transferToInterpreter();
     throw exceptionBuilder().typeMismatch(result, BaseModule.getIntClass()).build();
@@ -63,7 +63,7 @@ public abstract class ApplyVmFunction1Node extends ExpressionNode {
 
   public final VmCollection executeCollection(VmFunction function, Object arg1) {
     var result = execute(function, arg1);
-    if (result instanceof VmCollection) return (VmCollection) result;
+    if (result instanceof VmCollection collection) return collection;
 
     CompilerDirectives.transferToInterpreter();
     throw exceptionBuilder().typeMismatch(result, BaseModule.getCollectionClass()).build();

pkl-core/src/main/java/org/pkl/core/ast/lambda/ApplyVmFunction2Node.java

@@ -29,7 +29,7 @@ public abstract class ApplyVmFunction2Node extends PklNode {
 
   public final boolean executeBoolean(VmFunction function, Object arg1, Object arg2) {
     var result = execute(function, arg1, arg2);
-    if (result instanceof Boolean) return (Boolean) result;
+    if (result instanceof Boolean b) return b;
 
     CompilerDirectives.transferToInterpreter();
     throw exceptionBuilder().typeMismatch(result, BaseModule.getBooleanClass()).build();
@@ -37,7 +37,7 @@ public abstract class ApplyVmFunction2Node extends PklNode {
 
   public final VmCollection executeCollection(VmFunction function, Object arg1, Object arg2) {
     var result = execute(function, arg1, arg2);
-    if (result instanceof VmCollection) return (VmCollection) result;
+    if (result instanceof VmCollection collection) return collection;
 
     CompilerDirectives.transferToInterpreter();
     throw exceptionBuilder().typeMismatch(result, BaseModule.getCollectionClass()).build();
@@ -45,7 +45,7 @@ public abstract class ApplyVmFunction2Node extends PklNode {
 
   public final VmMap executeMap(VmFunction function, Object arg1, Object arg2) {
     var result = execute(function, arg1, arg2);
-    if (result instanceof VmMap) return (VmMap) result;
+    if (result instanceof VmMap map) return map;
 
     CompilerDirectives.transferToInterpreter();
     throw exceptionBuilder().typeMismatch(result, BaseModule.getMapClass()).build();
@@ -53,7 +53,7 @@ public abstract class ApplyVmFunction2Node extends PklNode {
 
   public final Long executeInt(VmFunction function, Object arg1, Object arg2) {
     var result = execute(function, arg1, arg2);
-    if (result instanceof Long) return (Long) result;
+    if (result instanceof Long l) return l;
 
     CompilerDirectives.transferToInterpreter();
     throw exceptionBuilder().typeMismatch(result, BaseModule.getIntClass()).build();
@@ -61,9 +61,7 @@ public abstract class ApplyVmFunction2Node extends PklNode {
 
   public final VmPair executePair(VmFunction function, Object arg1, Object arg2) {
     var result = execute(function, arg1, arg2);
-    if (result instanceof VmPair) {
+    if (result instanceof VmPair pair) return pair;
-      return (VmPair) result;
-    }
 
     CompilerDirectives.transferToInterpreter();
     throw exceptionBuilder().typeMismatch(result, BaseModule.getPairClass()).build();

pkl-core/src/main/java/org/pkl/core/ast/member/ModuleNode.java

@@ -54,8 +54,8 @@ public final class ModuleNode extends PklRootNode {
   @Override
   public Object execute(VirtualFrame frame) {
     var module = executeBody(frame, moduleNode);
-    if (module instanceof VmClass) {
+    if (module instanceof VmClass vmClass) {
-      return ((VmClass) module).getPrototype();
+      return vmClass.getPrototype();
     }
 
     assert module instanceof VmTyped;

pkl-core/src/main/java/org/pkl/core/ast/member/ObjectMember.java

@@ -106,8 +106,8 @@ public final class ObjectMember extends Member {
 
   public @Nullable Object getLocalPropertyDefaultValue() {
     assert isProp() && isLocal();
-    return getMemberNode() instanceof LocalTypedPropertyNode
+    return getMemberNode() instanceof LocalTypedPropertyNode propertyNode
-        ? ((LocalTypedPropertyNode) getMemberNode()).getDefaultValue()
+        ? propertyNode.getDefaultValue()
         : VmDynamic.empty();
   }
 

pkl-core/src/main/java/org/pkl/core/ast/member/UnresolvedMethodNode.java

@@ -97,7 +97,7 @@ public final class UnresolvedMethodNode extends UnresolvedClassMemberNode {
     for (var annotation : annotations) {
       if (annotation.getVmClass() == BaseModule.getDeprecatedClass()) {
         var messageObj = VmUtils.readMemberOrNull(annotation, Identifier.MESSAGE);
-        deprecation = messageObj instanceof String ? (String) messageObj : "";
+        deprecation = messageObj instanceof String string ? string : "";
         break;
       }
     }

pkl-core/src/main/java/org/pkl/core/ast/type/TypeNode.java

@@ -310,7 +310,7 @@ public abstract class TypeNode extends PklNode {
 
     @Override
     public void execute(VirtualFrame frame, Object value) {
-      if (value instanceof VmTyped && ((VmTyped) value).getVmClass() == moduleClass) return;
+      if (value instanceof VmTyped typed && typed.getVmClass() == moduleClass) return;
 
       throw typeMismatch(value, moduleClass);
     }
@@ -346,8 +346,8 @@ public abstract class TypeNode extends PklNode {
     public void execute(VirtualFrame frame, Object value) {
       var moduleClass = ((VmTyped) getModuleNode.executeGeneric(frame)).getVmClass();
 
-      if (value instanceof VmTyped) {
+      if (value instanceof VmTyped typed) {
-        var valueClass = ((VmTyped) value).getVmClass();
+        var valueClass = typed.getVmClass();
         if (moduleClass.isSuperclassOf(valueClass)) return;
       }
 
@@ -465,7 +465,7 @@ public abstract class TypeNode extends PklNode {
 
     @Override
     public void execute(VirtualFrame frame, Object value) {
-      if (value instanceof VmValue && clazz == ((VmValue) value).getVmClass()) return;
+      if (value instanceof VmValue vmValue && clazz == vmValue.getVmClass()) return;
 
       throw typeMismatch(value, clazz);
     }
@@ -1431,9 +1431,8 @@ public abstract class TypeNode extends PklNode {
 
     @Override
     public void execute(VirtualFrame frame, Object value) {
-      if (value instanceof Long) {
+      if (value instanceof Long l) {
-        var v = (long) value;
+        if ((l & mask) == l) return;
-        if ((v & mask) == v) return;
 
         throw new VmTypeMismatchException.Constraint(typeAlias.getConstraintSection(), value);
       }
@@ -1465,9 +1464,8 @@ public abstract class TypeNode extends PklNode {
 
     @Override
     public void execute(VirtualFrame frame, Object value) {
-      if (value instanceof Long) {
+      if (value instanceof Long l) {
-        var v = (long) value;
+        if (l == l.byteValue()) return;
-        if (v == (byte) v) return;
 
         throw new VmTypeMismatchException.Constraint(
             BaseModule.getInt8TypeAlias().getConstraintSection(), value);
@@ -1500,9 +1498,8 @@ public abstract class TypeNode extends PklNode {
 
     @Override
     public void execute(VirtualFrame frame, Object value) {
-      if (value instanceof Long) {
+      if (value instanceof Long l) {
-        var v = (long) value;
+        if (l == l.shortValue()) return;
-        if (v == (short) v) return;
 
         throw new VmTypeMismatchException.Constraint(
             BaseModule.getInt16TypeAlias().getConstraintSection(), value);
@@ -1535,9 +1532,8 @@ public abstract class TypeNode extends PklNode {
 
     @Override
     public void execute(VirtualFrame frame, Object value) {
-      if (value instanceof Long) {
+      if (value instanceof Long l) {
-        var v = (long) value;
+        if (l == l.intValue()) return;
-        if (v == (int) v) return;
 
         throw new VmTypeMismatchException.Constraint(
             BaseModule.getInt32TypeAlias().getConstraintSection(), value);
@@ -1836,21 +1832,21 @@ public abstract class TypeNode extends PklNode {
     @Override
     public void executeAndSet(VirtualFrame frame, Object value) {
       var kind = frame.getFrameDescriptor().getSlotKind(slot);
-      if (value instanceof Long) {
+      if (value instanceof Long l) {
         if (kind == FrameSlotKind.Double || kind == FrameSlotKind.Object) {
           frame.getFrameDescriptor().setSlotKind(slot, FrameSlotKind.Object);
-          frame.setObject(slot, value);
+          frame.setObject(slot, l);
         } else {
           frame.getFrameDescriptor().setSlotKind(slot, FrameSlotKind.Long);
-          frame.setLong(slot, (long) value);
+          frame.setLong(slot, l);
         }
-      } else if (value instanceof Double) {
+      } else if (value instanceof Double d) {
         if (kind == FrameSlotKind.Long || kind == FrameSlotKind.Object) {
           frame.getFrameDescriptor().setSlotKind(slot, FrameSlotKind.Object);
-          frame.setObject(slot, value);
+          frame.setObject(slot, d);
         } else {
           frame.getFrameDescriptor().setSlotKind(slot, FrameSlotKind.Double);
-          frame.setDouble(slot, (double) value);
+          frame.setDouble(slot, d);
         }
       } else {
         throw typeMismatch(value, BaseModule.getNumberClass());

pkl-core/src/main/java/org/pkl/core/ast/type/UnresolvedTypeNode.java

@@ -133,9 +133,7 @@ public abstract class UnresolvedTypeNode extends PklNode {
 
       var type = resolveTypeNode.executeGeneric(frame);
 
-      if (type instanceof VmClass) {
+      if (type instanceof VmClass clazz) {
-        VmClass clazz = (VmClass) type;
-
         // Note: FinalClassTypeNode and NonFinalClassTypeNode assume that
         // String/Boolean/Int/Float and their supertypes are handled separately.
 
@@ -163,9 +161,7 @@ public abstract class UnresolvedTypeNode extends PklNode {
         return TypeNode.forClass(sourceSection, clazz);
       }
 
-      if (type instanceof VmTypeAlias) {
+      if (type instanceof VmTypeAlias alias) {
-        var alias = (VmTypeAlias) type;
-
         if (alias.getModuleName().equals("pkl.base")) {
           switch (alias.getSimpleName()) {
             case "NonNull":
@@ -219,8 +215,7 @@ public abstract class UnresolvedTypeNode extends PklNode {
 
       var baseType = resolveTypeNode.executeGeneric(frame);
 
-      if (baseType instanceof VmClass) {
+      if (baseType instanceof VmClass clazz) {
-        var clazz = (VmClass) baseType;
         checkNumberOfTypeArguments(clazz);
 
         if (clazz.isCollectionClass()) {
@@ -289,8 +284,7 @@ public abstract class UnresolvedTypeNode extends PklNode {
             .build();
       }
 
-      if (baseType instanceof VmTypeAlias) {
+      if (baseType instanceof VmTypeAlias typeAlias) {
-        var typeAlias = (VmTypeAlias) baseType;
         var argLength = typeArgumentNodes.length;
         var resolvedTypeArgumentNodes = new TypeNode[argLength];
         for (var i = 0; i < argLength; i++) {

pkl-core/src/main/java/org/pkl/core/ast/type/VmTypeMismatchException.java

@@ -66,9 +66,9 @@ public abstract class VmTypeMismatchException extends ControlFlowException {
     public void describe(StringBuilder builder, String indent) {
       String renderedType;
       var valueFormatter = ValueFormatter.basic();
-      if (expectedType instanceof String) {
+      if (expectedType instanceof String string) {
         // string literal type
-        renderedType = valueFormatter.formatStringValue((String) expectedType, "");
+        renderedType = valueFormatter.formatStringValue(string, "");
       } else if (expectedType instanceof Set) {
         // union of string literal types
         @SuppressWarnings("unchecked")
@@ -90,10 +90,9 @@ public abstract class VmTypeMismatchException extends ControlFlowException {
       }
 
       // give better error than "expected foo.Bar, but got foo.Bar" in case of naming conflict
-      if (actualValue instanceof VmTyped && expectedType instanceof VmClass) {
+      if (actualValue instanceof VmTyped actualObj
-        var actualObj = (VmTyped) actualValue;
+          && expectedType instanceof VmClass expectedClass) {
         var actualClass = actualObj.getVmClass();
-        var expectedClass = (VmClass) expectedType;
         if (actualClass.getQualifiedName().equals(expectedClass.getQualifiedName())) {
           var actualModuleUri = actualClass.getModule().getModuleInfo().getModuleKey().getUri();
           var expectedModuleUri = expectedClass.getModule().getModuleInfo().getModuleKey().getUri();

pkl-core/src/main/java/org/pkl/core/http/RequestRewritingClient.java

@@ -90,14 +90,9 @@ final class RequestRewritingClient implements HttpClient {
             publisher -> builder.method(method, publisher),
             () -> {
               switch (method) {
-                case "GET":
+                case "GET" -> builder.GET();
-                  builder.GET();
+                case "DELETE" -> builder.DELETE();
-                  break;
+                default -> builder.method(method, HttpRequest.BodyPublishers.noBody());
-                case "DELETE":
-                  builder.DELETE();
-                  break;
-                default:
-                  builder.method(method, HttpRequest.BodyPublishers.noBody());
               }
             });
 

pkl-core/src/main/java/org/pkl/core/module/ModuleKeys.java

@@ -673,11 +673,11 @@ public final class ModuleKeys {
     }
 
     private @Nullable Path getLocalPath(Dependency dependency) {
-      if (!(dependency instanceof LocalDependency)) {
+      if (!(dependency instanceof LocalDependency localDependency)) {
         return null;
       }
-      return ((LocalDependency) dependency)
+      return localDependency.resolveAssetPath(
-          .resolveAssetPath(getProjectDepsResolver().getProjectDir(), packageAssetUri);
+          getProjectDepsResolver().getProjectDir(), packageAssetUri);
     }
 
     @Override

pkl-core/src/main/java/org/pkl/core/module/PathElement.java

@@ -64,15 +64,10 @@ public class PathElement {
   }
 
   @Override
-  public boolean equals(Object o) {
+  public boolean equals(Object obj) {
-    if (this == o) {
+    if (this == obj) return true;
-      return true;
+    if (!(obj instanceof PathElement other)) return false;
-    }
+    return isDirectory == other.isDirectory && name.equals(other.name);
-    if (!(o instanceof PathElement)) {
-      return false;
-    }
-    PathElement that = (PathElement) o;
-    return isDirectory == that.isDirectory && name.equals(that.name);
   }
 
   @Override

pkl-core/src/main/java/org/pkl/core/packages/DependencyMetadata.java

@@ -107,20 +107,18 @@ public class DependencyMetadata {
 
   private static Map<String, RemoteDependency> parseDependencies(Object deps)
       throws JsonParseException {
-    if (!(deps instanceof JsObject)) {
+    if (!(deps instanceof JsObject dependencies)) {
       throw new FormatException("object", deps.getClass());
     }
-    var dependencies = (JsObject) deps;
     var ret = new HashMap<String, RemoteDependency>(dependencies.size());
     for (var key : dependencies.keySet()) {
       var remoteDependency =
           dependencies.get(
               key,
               (dep) -> {
-                if (!(dep instanceof JsObject)) {
+                if (!(dep instanceof JsObject obj)) {
                   throw new FormatException("object", dep.getClass());
                 }
-                var obj = (JsObject) dep;
                 var checksums = obj.get("checksums", DependencyMetadata::parseChecksums);
                 var packageUri = obj.get("uri", PackageUtils::parsePackageUriWithoutChecksums);
                 return new RemoteDependency(packageUri, checksums);
@@ -131,25 +129,23 @@ public class DependencyMetadata {
   }
 
   public static Checksums parseChecksums(Object obj) throws JsonParseException {
-    if (!(obj instanceof JsObject)) {
+    if (!(obj instanceof JsObject jsObj)) {
       throw new FormatException("object", obj.getClass());
     }
-    var jsObj = (JsObject) obj;
     var sha256 = jsObj.getString("sha256");
     return new Checksums(sha256);
   }
 
   public static List<String> parseAuthors(Object obj) throws JsonParseException {
-    if (!(obj instanceof JsArray)) {
+    if (!(obj instanceof JsArray arr)) {
       throw new FormatException("array", obj.getClass());
     }
-    var arr = (JsArray) obj;
     var ret = new ArrayList<String>(arr.size());
     for (var elem : arr) {
-      if (!(elem instanceof String)) {
+      if (!(elem instanceof String string)) {
         throw new FormatException("string", elem.getClass());
       }
-      ret.add((String) elem);
+      ret.add(string);
     }
     return ret;
   }

pkl-core/src/main/java/org/pkl/core/packages/PackageUtils.java

@@ -23,10 +23,10 @@ import org.pkl.core.util.json.Json.JsonParseException;
 public class PackageUtils {
   public static PackageUri parsePackageUriWithoutChecksums(Object obj)
       throws JsonParseException, URISyntaxException {
-    if (!(obj instanceof String)) {
+    if (!(obj instanceof String string)) {
       throw new FormatException("string", obj.getClass());
     }
-    var packageUri = new PackageUri((String) obj);
+    var packageUri = new PackageUri(string);
     checkHasNoChecksumComponent(packageUri);
     return packageUri;
   }

pkl-core/src/main/java/org/pkl/core/parser/Parser.java

@@ -125,48 +125,48 @@ public class Parser {
 
     var curr = ctx.getChild(ctx.getChildCount() - 2); // last child before EOF
     while (curr.getChildCount() > 0) {
-      if (curr instanceof ClassBodyContext) {
+      if (curr instanceof ClassBodyContext classBody) {
-        if (((ClassBodyContext) curr).err == null) throw incompleteInput(curr, "}");
+        if (classBody.err == null) throw incompleteInput(curr, "}");
         else return;
       }
-      if (curr instanceof ParameterListContext) {
+      if (curr instanceof ParameterListContext parameterList) {
-        if (((ParameterListContext) curr).err == null) throw incompleteInput(curr, ")");
+        if (parameterList.err == null) throw incompleteInput(curr, ")");
         else return;
       }
-      if (curr instanceof ArgumentListContext) {
+      if (curr instanceof ArgumentListContext argumentList) {
-        if (((ArgumentListContext) curr).err == null) throw incompleteInput(curr, ")");
+        if (argumentList.err == null) throw incompleteInput(curr, ")");
         else return;
       }
-      if (curr instanceof TypeParameterListContext) {
+      if (curr instanceof TypeParameterListContext typeParameterList) {
-        if (((TypeParameterListContext) curr).err == null) throw incompleteInput(curr, ">");
+        if (typeParameterList.err == null) throw incompleteInput(curr, ">");
         else return;
       }
-      if (curr instanceof TypeArgumentListContext) {
+      if (curr instanceof TypeArgumentListContext typeArgumentList) {
-        if (((TypeArgumentListContext) curr).err == null) throw incompleteInput(curr, ">");
+        if (typeArgumentList.err == null) throw incompleteInput(curr, ">");
         else return;
       }
-      if (curr instanceof ParenthesizedTypeContext) {
+      if (curr instanceof ParenthesizedTypeContext parenthesizedType) {
-        if (((ParenthesizedTypeContext) curr).err == null) throw incompleteInput(curr, ")");
+        if (parenthesizedType.err == null) throw incompleteInput(curr, ")");
         else return;
       }
-      if (curr instanceof ConstrainedTypeContext) {
+      if (curr instanceof ConstrainedTypeContext constrainedType) {
-        if (((ConstrainedTypeContext) curr).err == null) throw incompleteInput(curr, ")");
+        if (constrainedType.err == null) throw incompleteInput(curr, ")");
         else return;
       }
-      if (curr instanceof ParenthesizedExprContext) {
+      if (curr instanceof ParenthesizedExprContext parenthesizedExpr) {
-        if (((ParenthesizedExprContext) curr).err == null) throw incompleteInput(curr, ")");
+        if (parenthesizedExpr.err == null) throw incompleteInput(curr, ")");
         else return;
       }
-      if (curr instanceof SuperSubscriptExprContext) {
+      if (curr instanceof SuperSubscriptExprContext superSubscriptExpr) {
-        if (((SuperSubscriptExprContext) curr).err == null) throw incompleteInput(curr, "]");
+        if (superSubscriptExpr.err == null) throw incompleteInput(curr, "]");
         else return;
       }
-      if (curr instanceof SubscriptExprContext) {
+      if (curr instanceof SubscriptExprContext subscriptExpr) {
-        if (((SubscriptExprContext) curr).err == null) throw incompleteInput(curr, "]");
+        if (subscriptExpr.err == null) throw incompleteInput(curr, "]");
         else return;
       }
-      if (curr instanceof ObjectBodyContext) {
+      if (curr instanceof ObjectBodyContext objectBody) {
-        if (((ObjectBodyContext) curr).err == null) throw incompleteInput(curr, "}");
+        if (objectBody.err == null) throw incompleteInput(curr, "}");
         else return;
       }
       curr = curr.getChild(curr.getChildCount() - 1);

pkl-core/src/main/java/org/pkl/core/project/Project.java

@@ -131,8 +131,8 @@ public final class Project {
     PackageUtils.checkHasNoChecksumComponent(packageUri);
     var objChecksum = object.getProperty("checksums");
     Checksums checksums = null;
-    if (objChecksum instanceof PObject) {
+    if (objChecksum instanceof PObject pObject) {
-      var sha256 = (String) ((PObject) objChecksum).get("sha256");
+      var sha256 = (String) pObject.get("sha256");
       assert sha256 != null;
       checksums = new Checksums(sha256);
     }

pkl-core/src/main/java/org/pkl/core/project/ProjectDeps.java

@@ -99,10 +99,9 @@ public class ProjectDeps {
 
   private static EconomicMap<CanonicalPackageUri, Dependency> parseResolvedDependencies(
       Object object) throws JsonParseException, URISyntaxException {
-    if (!(object instanceof JsObject)) {
+    if (!(object instanceof JsObject jsObj)) {
       throw new FormatException("resolvedDependencies", "object", object.getClass());
     }
-    var jsObj = (JsObject) object;
     var ret = EconomicMaps.<CanonicalPackageUri, Dependency>create(jsObj.size());
     for (var entry : jsObj.entrySet()) {
       Dependency resolvedDependency = parseResolvedDependency(entry);
@@ -115,10 +114,9 @@ public class ProjectDeps {
   private static Dependency parseResolvedDependency(Entry<String, Object> entry)
       throws JsonParseException {
     var input = entry.getValue();
-    if (!(input instanceof JsObject)) {
+    if (!(input instanceof JsObject obj)) {
       throw new VmExceptionBuilder().evalError("invalid object").build();
     }
-    var obj = (JsObject) input;
     var type = obj.getString("type");
     var uri = obj.get("uri", PackageUtils::parsePackageUriWithoutChecksums);
     if (type.equals("remote")) {
@@ -211,8 +209,8 @@ public class ProjectDeps {
       while (cursor.advance()) {
         jsonWriter.name(cursor.getKey().toString());
         var dependency = cursor.getValue();
-        if (dependency instanceof LocalDependency) {
+        if (dependency instanceof LocalDependency localDependency) {
-          writeLocalDependency((LocalDependency) dependency);
+          writeLocalDependency(localDependency);
         } else {
           writeRemoteDependency((RemoteDependency) dependency);
         }

pkl-core/src/main/java/org/pkl/core/repl/ReplServer.java

@@ -116,16 +116,16 @@ public class ReplServer implements AutoCloseable {
   public List<ReplResponse> handleRequest(ReplRequest request) {
     polyglotContext.enter();
     try {
-      if (request instanceof Eval) {
+      if (request instanceof Eval eval) {
-        return handleEval((Eval) request);
+        return handleEval(eval);
       }
 
-      if (request instanceof Load) {
+      if (request instanceof Load load) {
-        return handleLoad((Load) request);
+        return handleLoad(load);
       }
 
-      if (request instanceof ReplRequest.Completion) {
+      if (request instanceof ReplRequest.Completion completion) {
-        return handleCompletion((ReplRequest.Completion) request);
+        return handleCompletion(completion);
       }
 
       if (request instanceof Reset) {
@@ -157,8 +157,8 @@ public class ReplServer implements AutoCloseable {
     return results.stream()
         .map(
             result ->
-                result instanceof ReplResponse
+                result instanceof ReplResponse response
-                    ? (ReplResponse) result
+                    ? response
                     : new EvalSuccess(render(result)))
         .collect(Collectors.toList());
   }
@@ -210,20 +210,20 @@ public class ReplServer implements AutoCloseable {
         if (tree instanceof ExprContext) {
           var exprNode = (ExpressionNode) tree.accept(builder);
           evaluateExpr(replState, exprNode, forceResults, results);
-        } else if (tree instanceof ImportClauseContext) {
+        } else if (tree instanceof ImportClauseContext importClause) {
-          addStaticModuleProperty(builder.visitImportClause((ImportClauseContext) tree));
+          addStaticModuleProperty(builder.visitImportClause(importClause));
-        } else if (tree instanceof ClassPropertyContext) {
+        } else if (tree instanceof ClassPropertyContext classProperty) {
-          var propertyNode = builder.visitClassProperty((ClassPropertyContext) tree);
+          var propertyNode = builder.visitClassProperty(classProperty);
           var property = addModuleProperty(propertyNode);
           if (evalDefinitions) {
             evaluateMemberDef(replState, property, forceResults, results);
           }
-        } else if (tree instanceof ClazzContext) {
+        } else if (tree instanceof ClazzContext clazz) {
-          addStaticModuleProperty(builder.visitClazz((ClazzContext) tree));
+          addStaticModuleProperty(builder.visitClazz(clazz));
-        } else if (tree instanceof TypeAliasContext) {
+        } else if (tree instanceof TypeAliasContext typeAlias) {
-          addStaticModuleProperty(builder.visitTypeAlias((TypeAliasContext) tree));
+          addStaticModuleProperty(builder.visitTypeAlias(typeAlias));
-        } else if (tree instanceof ClassMethodContext) {
+        } else if (tree instanceof ClassMethodContext classMethod) {
-          addModuleMethodDef(builder.visitClassMethod((ClassMethodContext) tree));
+          addModuleMethodDef(builder.visitClassMethod(classMethod));
         } else if (tree instanceof ModuleDeclContext) {
           // do nothing for now
         } else if (tree instanceof TerminalNode && tree.toString().equals(",")) {
@@ -360,8 +360,8 @@ public class ReplServer implements AutoCloseable {
     assert !(lastResult instanceof ReplResponse);
 
     VmObjectLike composite;
-    if (lastResult instanceof VmObjectLike) {
+    if (lastResult instanceof VmObjectLike objectLike) {
-      composite = (VmObjectLike) lastResult;
+      composite = objectLike;
     } else {
       composite = VmUtils.getClass(lastResult).getPrototype();
     }

pkl-core/src/main/java/org/pkl/core/resource/ResourceReaders.java

@@ -556,11 +556,11 @@ public final class ResourceReaders {
     }
 
     private @Nullable Path getLocalPath(Dependency dependency, PackageAssetUri packageAssetUri) {
-      if (!(dependency instanceof LocalDependency)) {
+      if (!(dependency instanceof LocalDependency localDependency)) {
         return null;
       }
-      return ((LocalDependency) dependency)
+      return localDependency.resolveAssetPath(
-          .resolveAssetPath(getProjectDepsResolver().getProjectDir(), packageAssetUri);
+          getProjectDepsResolver().getProjectDir(), packageAssetUri);
     }
   }
 

pkl-core/src/main/java/org/pkl/core/runtime/BaseModule.java

@@ -136,24 +136,19 @@ public final class BaseModule extends StdLibModule {
   }
 
   public static VmClass getFunctionNClass(int paramCount) {
-    switch (paramCount) {
+    return switch (paramCount) {
-      case 0:
+      case 0 -> getFunction0Class();
-        return getFunction0Class();
+      case 1 -> getFunction1Class();
-      case 1:
+      case 2 -> getFunction2Class();
-        return getFunction1Class();
+      case 3 -> getFunction3Class();
-      case 2:
+      case 4 -> getFunction4Class();
-        return getFunction2Class();
+      case 5 -> getFunction5Class();
-      case 3:
+      default -> {
-        return getFunction3Class();
-      case 4:
-        return getFunction4Class();
-      case 5:
-        return getFunction5Class();
-      default:
         CompilerDirectives.transferToInterpreter();
         throw new IllegalArgumentException(
             String.format("Class `Function%d` does not exist.", paramCount));
-    }
+      }
+    };
   }
 
   public static VmClass getFunction0Class() {

pkl-core/src/main/java/org/pkl/core/runtime/KeyLookupSuggestions.java

@@ -33,8 +33,7 @@ public class KeyLookupSuggestions {
 
     map.forEach(
         entry -> {
-          if (!(entry.getKey() instanceof String)) return;
+          if (!(entry.getKey() instanceof String entryKey)) return;
-          var entryKey = (String) entry.getKey();
           var similarity = STRING_SIMILARITY.similarity(entryKey, key);
           if (similarity >= SIMILARITY_THRESHOLD) {
             candidates.add(new Candidate(entryKey, similarity));
@@ -50,8 +49,7 @@ public class KeyLookupSuggestions {
 
     object.iterateMemberValues(
         (memberKey, member, value) -> {
-          if (!(memberKey instanceof String)) return true;
+          if (!(memberKey instanceof String stringKey)) return true;
-          var stringKey = (String) memberKey;
           var similarity = STRING_SIMILARITY.similarity(stringKey, key);
           if (similarity >= SIMILARITY_THRESHOLD) {
             candidates.add(new Candidate(stringKey, similarity));
@@ -80,7 +78,7 @@ public class KeyLookupSuggestions {
 
     @Override
     public boolean equals(@Nullable Object obj) {
-      return (obj instanceof Candidate && ((Candidate) obj).key.equals(key));
+      return (obj instanceof Candidate candidate && candidate.key.equals(key));
     }
 
     @Override

pkl-core/src/main/java/org/pkl/core/runtime/MemberLookupSuggestions.java

@@ -144,9 +144,7 @@ public class MemberLookupSuggestions {
     @Override
     public boolean equals(@Nullable Object obj) {
       if (this == obj) return true;
-      if (!(obj instanceof Candidate)) return false;
+      if (!(obj instanceof Candidate other)) return false;
-
-      var other = (Candidate) obj;
       // member lookup is name rather than signature based (but distinguishes kind)
       return kind == other.kind && name.equals(other.name);
     }

pkl-core/src/main/java/org/pkl/core/runtime/MinPklVersionChecker.java

@@ -45,9 +45,9 @@ final class MinPklVersionChecker {
   }
 
   static void check(String moduleName, @Nullable ParserRuleContext ctx, @Nullable Node importNode) {
-    if (!(ctx instanceof ModuleContext)) return;
+    if (!(ctx instanceof ModuleContext moduleCtx)) return;
 
-    var moduleDeclCtx = ((ModuleContext) ctx).moduleDecl();
+    var moduleDeclCtx = moduleCtx.moduleDecl();
     if (moduleDeclCtx == null) return;
 
     for (var annCtx : moduleDeclCtx.annotation()) {
@@ -57,9 +57,8 @@ final class MinPklVersionChecker {
       if (objectBodyCtx == null) continue;
 
       for (var memberCtx : objectBodyCtx.objectMember()) {
-        if (!(memberCtx instanceof ObjectPropertyContext)) continue;
+        if (!(memberCtx instanceof ObjectPropertyContext propertyCtx)) continue;
 
-        var propertyCtx = (ObjectPropertyContext) memberCtx;
         if (!Identifier.MIN_PKL_VERSION.toString().equals(getText(propertyCtx.Identifier())))
           continue;
 
@@ -84,8 +83,7 @@ final class MinPklVersionChecker {
   }
 
   private static @Nullable String getLastIdText(@Nullable TypeContext typeCtx) {
-    if (!(typeCtx instanceof DeclaredTypeContext)) return null;
+    if (!(typeCtx instanceof DeclaredTypeContext declCtx)) return null;
-    var declCtx = (DeclaredTypeContext) typeCtx;
     var token = declCtx.qualifiedIdentifier().Identifier;
     return token == null ? null : token.getText();
   }

pkl-core/src/main/java/org/pkl/core/runtime/MirrorFactories.java

@@ -203,16 +203,12 @@ public final class MirrorFactories {
         .addStringProperty("name", TypeParameter::getName)
         .addProperty(
             "variance",
-            typeParameter -> {
+            typeParameter ->
-              switch (typeParameter.getVariance()) {
+                switch (typeParameter.getVariance()) {
-                case COVARIANT:
+                  case COVARIANT -> "out";
-                  return "out";
+                  case CONTRAVARIANT -> "in";
-                case CONTRAVARIANT:
+                  default -> VmNull.withoutDefault();
-                  return "in";
+                });
-                default:
-                  return VmNull.withoutDefault();
-              }
-            });
 
     classTypeFactory
         .addTypedProperty(

pkl-core/src/main/java/org/pkl/core/runtime/ModuleCache.java

@@ -135,7 +135,7 @@ public final class ModuleCache {
 
     var module1 = modulesByOriginalUri.get(moduleKey.getUri());
     if (module1 != null) {
-      if (module1 instanceof VmTyped) return (VmTyped) module1;
+      if (module1 instanceof VmTyped typed) return typed;
 
       assert module1 instanceof RuntimeException;
       // would be more accurate/safe to throw a clone with adapted Pkl stack trace
@@ -145,7 +145,7 @@ public final class ModuleCache {
     var resolvedKey = resolve(moduleKey, securityManager, importNode);
     var module2 = modulesByResolvedUri.get(resolvedKey.getUri());
     if (module2 != null) {
-      if (module2 instanceof VmTyped) return (VmTyped) module2;
+      if (module2 instanceof VmTyped typed) return typed;
 
       assert module2 instanceof RuntimeException;
       // would be more accurate/safe to throw a clone with adapted Pkl stack trace

pkl-core/src/main/java/org/pkl/core/runtime/ResourceManager.java

@@ -160,8 +160,8 @@ public final class ResourceManager {
           var res = resource.get();
           if (res instanceof String) return resource;
 
-          if (res instanceof Resource) {
+          if (res instanceof Resource r) {
-            return Optional.of(resourceFactory.create((Resource) res));
+            return Optional.of(resourceFactory.create(r));
           }
 
           throw new VmExceptionBuilder()

pkl-core/src/main/java/org/pkl/core/runtime/StackTraceGenerator.java

@@ -66,12 +66,12 @@ class StackTraceGenerator {
 
     for (Node current = callNode; current != null; current = current.getParent()) {
       if (current.getSourceSection() != null) {
-        return current instanceof MemberNode
+        return current instanceof MemberNode memberNode
             // Always display the member body's source section instead of the member
             // (root) node's source section (which includes doc comment etc.), even
             // if `callNode` is a child of root node rather than body node.
             // This improves stack trace output for failed property type checks.
-            ? ((MemberNode) current).getBodySection()
+            ? memberNode.getBodySection()
             : current.getSourceSection();
       }
     }

pkl-core/src/main/java/org/pkl/core/runtime/StackTraceRenderer.java

@@ -41,8 +41,7 @@ public class StackTraceRenderer {
       String leftMargin,
       boolean isFirstElement) {
     for (var frame : frames) {
-      if (frame instanceof StackFrameLoop) {
+      if (frame instanceof StackFrameLoop loop) {
-        var loop = (StackFrameLoop) frame;
         // ensure a cycle of length 1 doesn't get rendered as a loop
         if (loop.count == 1) {
           doRender(loop.frames, null, builder, leftMargin, isFirstElement);

pkl-core/src/main/java/org/pkl/core/runtime/VmCollection.java

@@ -129,10 +129,9 @@ public abstract class VmCollection extends VmValue implements Iterable<Object> {
   public final VmCollection flatten() {
     var builder = builder();
     for (var elem : this) {
-      if (elem instanceof Iterable) {
+      if (elem instanceof Iterable<?> iterable) {
-        builder.addAll((Iterable<?>) elem);
+        builder.addAll(iterable);
-      } else if (elem instanceof VmListing) {
+      } else if (elem instanceof VmListing listing) {
-        var listing = (VmListing) elem;
         listing.forceAndIterateMemberValues(
             (key, member, value) -> {
               builder.add(value);

pkl-core/src/main/java/org/pkl/core/runtime/VmDataSize.java

@@ -144,9 +144,7 @@ public final class VmDataSize extends VmValue implements Comparable<VmDataSize>
   @Override
   public boolean equals(@Nullable Object obj) {
     if (this == obj) return true;
-    if (!(obj instanceof VmDataSize)) return false;
+    if (!(obj instanceof VmDataSize other)) return false;
-
-    var other = (VmDataSize) obj;
     // converting to a fixed unit guarantees that equals() is commutative and consistent with
     // hashCode()
     return convertValueTo(DataSizeUnit.BYTES) == other.convertValueTo(DataSizeUnit.BYTES);

pkl-core/src/main/java/org/pkl/core/runtime/VmDuration.java

@@ -140,9 +140,7 @@ public final class VmDuration extends VmValue implements Comparable<VmDuration>
   @Override
   public boolean equals(@Nullable Object obj) {
     if (this == obj) return true;
-    if (!(obj instanceof VmDuration)) return false;
+    if (!(obj instanceof VmDuration other)) return false;
-
-    var other = (VmDuration) obj;
     // converting to a fixed unit guarantees that equals() is commutative and consistent with
     // hashCode()
     return getValue(DurationUnit.NANOS) == other.getValue(DurationUnit.NANOS);

pkl-core/src/main/java/org/pkl/core/runtime/VmDynamic.java

@@ -101,9 +101,8 @@ public final class VmDynamic extends VmObject {
   @TruffleBoundary
   public boolean equals(Object obj) {
     if (this == obj) return true;
-    if (!(obj instanceof VmDynamic)) return false;
+    if (!(obj instanceof VmDynamic other)) return false;
 
-    var other = (VmDynamic) obj;
     // could use shallow force, but deep force is cached
     force(false);
     other.force(false);

pkl-core/src/main/java/org/pkl/core/runtime/VmExceptionBuilder.java

@@ -127,11 +127,11 @@ public class VmExceptionBuilder {
   }
 
   public VmExceptionBuilder cannotFindMember(VmObjectLike receiver, Object memberKey) {
-    if (memberKey instanceof Identifier) {
+    if (memberKey instanceof Identifier identifier) {
-      return cannotFindProperty(receiver, (Identifier) memberKey, true, false);
+      return cannotFindProperty(receiver, identifier, true, false);
     }
-    if (memberKey instanceof String) {
+    if (memberKey instanceof String string) {
-      var candidates = KeyLookupSuggestions.forObject(receiver, (String) memberKey);
+      var candidates = KeyLookupSuggestions.forObject(receiver, string);
       if (!candidates.isEmpty()) {
         return evalError(
             "cannotFindKeyListCandidates",
@@ -245,8 +245,8 @@ public class VmExceptionBuilder {
   }
 
   public VmExceptionBuilder cannotFindKey(VmMap map, Object key) {
-    if (key instanceof String) {
+    if (key instanceof String string) {
-      var candidates = KeyLookupSuggestions.forMap(map, (String) key);
+      var candidates = KeyLookupSuggestions.forMap(map, string);
       if (!candidates.isEmpty()) {
         return evalError(
             "cannotFindKeyListCandidates",
@@ -334,44 +334,42 @@ public class VmExceptionBuilder {
       throw new IllegalStateException("No message set.");
     }
 
-    switch (kind) {
+    return switch (kind) {
-      case EVAL_ERROR:
+      case EVAL_ERROR ->
-        return new VmEvalException(
+          new VmEvalException(
-            message,
+              message,
-            cause,
+              cause,
-            isExternalMessage,
+              isExternalMessage,
-            messageArguments,
+              messageArguments,
-            programValues,
+              programValues,
-            location,
+              location,
-            sourceSection,
+              sourceSection,
-            memberName,
+              memberName,
-            hint);
+              hint);
-      case UNDEFINED_VALUE:
+      case UNDEFINED_VALUE ->
-        return new VmUndefinedValueException(
+          new VmUndefinedValueException(
-            message,
+              message,
-            cause,
+              cause,
-            isExternalMessage,
+              isExternalMessage,
-            messageArguments,
+              messageArguments,
-            programValues,
+              programValues,
-            location,
+              location,
-            sourceSection,
+              sourceSection,
-            memberName,
+              memberName,
-            hint,
+              hint,
-            receiver);
+              receiver);
-      case BUG:
+      case BUG ->
-        return new VmBugException(
+          new VmBugException(
-            message,
+              message,
-            cause,
+              cause,
-            isExternalMessage,
+              isExternalMessage,
-            messageArguments,
+              messageArguments,
-            programValues,
+              programValues,
-            location,
+              location,
-            sourceSection,
+              sourceSection,
-            memberName,
+              memberName,
-            hint);
+              hint);
-      default:
+    };
-        throw unreachableCode().build();
-    }
   }
 
   private List<Identifier> collectPropertyNames(VmObjectLike object, boolean isRead) {

pkl-core/src/main/java/org/pkl/core/runtime/VmExceptionRenderer.java

@@ -43,8 +43,8 @@ public class VmExceptionRenderer {
   }
 
   private void render(VmException exception, StringBuilder builder) {
-    if (exception instanceof VmBugException) {
+    if (exception instanceof VmBugException bugException) {
-      renderBugException((VmBugException) exception, builder);
+      renderBugException(bugException, builder);
     } else {
       renderException(exception, builder);
     }

pkl-core/src/main/java/org/pkl/core/runtime/VmFunction.java

@@ -60,7 +60,7 @@ public final class VmFunction extends VmObjectLike {
 
   public String applyString(Object arg1) {
     var result = apply(arg1);
-    if (result instanceof String) return (String) result;
+    if (result instanceof String string) return string;
 
     CompilerDirectives.transferToInterpreter();
     throw new VmExceptionBuilder().typeMismatch(result, BaseModule.getStringClass()).build();

pkl-core/src/main/java/org/pkl/core/runtime/VmIntSeq.java

@@ -107,9 +107,7 @@ public final class VmIntSeq extends VmValue implements Iterable<Long> {
   @Override
   public boolean equals(@Nullable Object obj) {
     if (this == obj) return true;
-    if (!(obj instanceof VmIntSeq)) return false;
+    if (!(obj instanceof VmIntSeq other)) return false;
-
-    var other = (VmIntSeq) obj;
     return isEmpty()
         ? other.isEmpty()
         : start == other.start && last == other.last && step == other.step;

pkl-core/src/main/java/org/pkl/core/runtime/VmList.java

@@ -424,8 +424,8 @@ public final class VmList extends VmCollection {
   public boolean equals(@Nullable Object other) {
     if (this == other) return true;
     //noinspection SimplifiableIfStatement
-    if (!(other instanceof VmList)) return false;
+    if (!(other instanceof VmList list)) return false;
-    return rrbt.equals(((VmList) other).rrbt);
+    return rrbt.equals(list.rrbt);
   }
 
   @Override

pkl-core/src/main/java/org/pkl/core/runtime/VmListing.java

@@ -104,9 +104,8 @@ public final class VmListing extends VmObject {
   @TruffleBoundary
   public boolean equals(@Nullable Object obj) {
     if (this == obj) return true;
-    if (!(obj instanceof VmListing)) return false;
+    if (!(obj instanceof VmListing other)) return false;
 
-    var other = (VmListing) obj;
     if (length != other.length) return false;
     // could use shallow force, but deep force is cached
     force(false);

pkl-core/src/main/java/org/pkl/core/runtime/VmMap.java

@@ -245,8 +245,8 @@ public final class VmMap extends VmValue implements Iterable<Map.Entry<Object, O
   public boolean equals(@Nullable Object other) {
     if (this == other) return true;
     //noinspection SimplifiableIfStatement
-    if (!(other instanceof VmMap)) return false;
+    if (!(other instanceof VmMap vmMap)) return false;
-    return map.equals(((VmMap) other).map);
+    return map.equals(vmMap.map);
   }
 
   @Override

pkl-core/src/main/java/org/pkl/core/runtime/VmMapping.java

@@ -68,8 +68,7 @@ public final class VmMapping extends VmObject {
     synchronized (this) {
       if (__allKeys == null) {
         // building upon parent's `getAllKeys()` should improve at least worst case efficiency
-        var parentKeys =
+        var parentKeys = parent instanceof VmMapping mapping ? mapping.getAllKeys() : VmSet.EMPTY;
-            parent instanceof VmMapping ? ((VmMapping) parent).getAllKeys() : VmSet.EMPTY;
         var builder = VmSet.builder(parentKeys);
         for (var cursor = members.getEntries(); cursor.advance(); ) {
           var member = cursor.getValue();
@@ -127,9 +126,8 @@ public final class VmMapping extends VmObject {
   @TruffleBoundary
   public boolean equals(Object obj) {
     if (this == obj) return true;
-    if (!(obj instanceof VmMapping)) return false;
+    if (!(obj instanceof VmMapping other)) return false;
 
-    var other = (VmMapping) obj;
     // could use shallow force, but deep force is cached
     force(false);
     other.force(false);

pkl-core/src/main/java/org/pkl/core/runtime/VmPair.java

@@ -54,14 +54,11 @@ public final class VmPair extends VmValue implements Iterable<Object> {
 
       @Override
       public Object next() {
-        switch (pos++) {
+        return switch (pos++) {
-          case 0:
+          case 0 -> first;
-            return first;
+          case 1 -> second;
-          case 1:
+          default -> throw new NoSuchElementException("VmPair only has two elements.");
-            return second;
+        };
-          default:
-            throw new NoSuchElementException("VmPair only has two elements.");
-        }
       }
     };
   }
@@ -105,9 +102,7 @@ public final class VmPair extends VmValue implements Iterable<Object> {
   @TruffleBoundary
   public boolean equals(@Nullable Object obj) {
     if (this == obj) return true;
-    if (!(obj instanceof VmPair)) return false;
+    if (!(obj instanceof VmPair other)) return false;
-
-    var other = (VmPair) obj;
     return first.equals(other.first) && second.equals(other.second);
   }
 

pkl-core/src/main/java/org/pkl/core/runtime/VmRegex.java

@@ -67,9 +67,7 @@ public final class VmRegex extends VmValue {
   @Override
   public boolean equals(@Nullable Object obj) {
     if (this == obj) return true;
-    if (!(obj instanceof VmRegex)) return false;
+    if (!(obj instanceof VmRegex other)) return false;
-
-    var other = (VmRegex) obj;
     return pattern.pattern().equals(other.pattern.pattern());
   }
 

pkl-core/src/main/java/org/pkl/core/runtime/VmSet.java

@@ -324,8 +324,8 @@ public final class VmSet extends VmCollection {
   public boolean equals(@Nullable Object other) {
     if (this == other) return true;
     //noinspection SimplifiableIfStatement
-    if (!(other instanceof VmSet)) return false;
+    if (!(other instanceof VmSet vmSet)) return false;
-    return set.equals(((VmSet) other).set);
+    return set.equals(vmSet.set);
   }
 
   @Override

pkl-core/src/main/java/org/pkl/core/runtime/VmTypeAlias.java

@@ -98,8 +98,8 @@ public final class VmTypeAlias extends VmValue {
    */
   @TruffleBoundary
   public SourceSection getBaseTypeSection() {
-    if (typeNode instanceof ConstrainedTypeNode) {
+    if (typeNode instanceof ConstrainedTypeNode constrainedTypeNode) {
-      return ((ConstrainedTypeNode) typeNode).getBaseTypeSection();
+      return constrainedTypeNode.getBaseTypeSection();
     }
 
     throw new VmExceptionBuilder()
@@ -176,8 +176,7 @@ public final class VmTypeAlias extends VmValue {
 
     clone.accept(
         node -> {
-          if (node instanceof TypeVariableNode) {
+          if (node instanceof TypeVariableNode typeVarNode) {
-            var typeVarNode = (TypeVariableNode) node;
             int index = typeVarNode.getTypeParameterIndex();
             // should not need to clone type argument node because it is not used by its original
             // root node

pkl-core/src/main/java/org/pkl/core/runtime/VmTyped.java

@@ -177,9 +177,8 @@ public final class VmTyped extends VmObject {
   @TruffleBoundary
   public boolean equals(@Nullable Object obj) {
     if (this == obj) return true;
-    if (!(obj instanceof VmTyped)) return false;
+    if (!(obj instanceof VmTyped other)) return false;
 
-    var other = (VmTyped) obj;
     if (clazz != other.clazz) return false;
     // could use shallow force, but deep force is cached
     force(false);

pkl-core/src/main/java/org/pkl/core/runtime/VmUndefinedValueException.java

@@ -60,11 +60,10 @@ public final class VmUndefinedValueException extends VmEvalException {
     renderPath(builder, path);
     builder.append('`');
     path.pop();
-    if (topLevelValue instanceof VmTyped && ((VmTyped) topLevelValue).isModuleObject()) {
+    if (topLevelValue instanceof VmTyped typed && typed.isModuleObject()) {
-      var modl = (VmTyped) topLevelValue;
       builder
           .append(" of module `")
-          .append(modl.getModuleInfo().getModuleSchema(modl).getModuleUri())
+          .append(typed.getModuleInfo().getModuleSchema(typed).getModuleUri())
           .append('`');
     }
     builder.append('.');

pkl-core/src/main/java/org/pkl/core/runtime/VmUtils.java

@@ -233,7 +233,7 @@ public final class VmUtils {
   @TruffleBoundary
   public static @Nullable Object readMemberOrNull(
       VmObjectLike receiver, Object memberKey, boolean checkType, IndirectCallNode callNode) {
-    assert (!(memberKey instanceof Identifier) || !((Identifier) memberKey).isLocalProp())
+    assert (!(memberKey instanceof Identifier identifier) || !identifier.isLocalProp())
         : "Must use ReadLocalPropertyNode for local properties.";
 
     final var cachedValue = receiver.getCachedValue(memberKey);
@@ -329,12 +329,12 @@ public final class VmUtils {
   }
 
   public static boolean isRenderDirective(Object value) {
-    return value instanceof VmTyped && isRenderDirective((VmTyped) value);
+    return value instanceof VmTyped typed && isRenderDirective(typed);
   }
 
   public static boolean isPcfRenderDirective(Object value) {
-    return value instanceof VmTyped
+    return value instanceof VmTyped typed
-        && ((VmTyped) value).getVmClass().getPClassInfo() == PClassInfo.PcfRenderDirective;
+        && typed.getVmClass().getPClassInfo() == PClassInfo.PcfRenderDirective;
   }
 
   @TruffleBoundary
@@ -348,8 +348,8 @@ public final class VmUtils {
 
   // implements same behavior as AnyNodes#getClass
   public static VmClass getClass(Object value) {
-    if (value instanceof VmValue) {
+    if (value instanceof VmValue vmValue) {
-      return ((VmValue) value).getVmClass();
+      return vmValue.getVmClass();
     }
     if (value instanceof String) {
       return BaseModule.getStringClass();
@@ -627,8 +627,8 @@ public final class VmUtils {
     // because constant type check wouldn't find the property (type)
     var isLocalTyped = property.isLocal() && typeNode != null;
 
-    if (bodyNode instanceof ConstantNode && !isLocalTyped) {
+    if (bodyNode instanceof ConstantNode constantNode && !isLocalTyped) {
-      property.initConstantValue((ConstantNode) bodyNode);
+      property.initConstantValue(constantNode);
       return property;
     }
 
@@ -661,8 +661,8 @@ public final class VmUtils {
     // because constant type check wouldn't find the property (type)
     var isLocalTyped = property.isLocal() && typeNode != null;
 
-    if (bodyNode instanceof ConstantNode && !isLocalTyped) {
+    if (bodyNode instanceof ConstantNode constantNode && !isLocalTyped) {
-      property.initConstantValue((ConstantNode) bodyNode);
+      property.initConstantValue(constantNode);
       return property;
     }