Use instanceof pattern matching

error-prone-contrib/src/main/java/tech/picnic/errorprone/bugpatterns/AmbiguousJsonCreator.java

@@ -18,7 +18,7 @@
 import com.sun.source.tree.AnnotationTree;
 import com.sun.source.tree.ClassTree;
 import com.sun.source.tree.MethodTree;
-import com.sun.source.tree.Tree;
+import com.sun.source.tree.Tree.Kind;
 import com.sun.tools.javac.code.Symbol;
 import java.util.Map;
 import javax.lang.model.element.AnnotationValue;
@@ -46,7 +46,7 @@ public Description matchAnnotation(AnnotationTree tree, VisitorState state) {
     }
 
     ClassTree clazz = state.findEnclosing(ClassTree.class);
-    if (clazz == null || clazz.getKind() != Tree.Kind.ENUM) {
+    if (clazz == null || clazz.getKind() != Kind.ENUM) {
       return Description.NO_MATCH;
     }
 

error-prone-contrib/src/main/java/tech/picnic/errorprone/bugpatterns/CanonicalAnnotationSyntax.java

@@ -19,7 +19,6 @@
 import com.sun.source.tree.AssignmentTree;
 import com.sun.source.tree.ExpressionTree;
 import com.sun.source.tree.NewArrayTree;
-import com.sun.source.tree.Tree.Kind;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Optional;
@@ -119,7 +118,7 @@ private static Optional<Fix> dropRedundantCurlies(AnnotationTree tree, VisitorSt
        * the expression as a whole.
        */
       ExpressionTree value =
-          (arg.getKind() == Kind.ASSIGNMENT) ? ((AssignmentTree) arg).getExpression() : arg;
+          (arg instanceof AssignmentTree assignment) ? assignment.getExpression() : arg;
 
       /* Store a fix for each expression that was successfully simplified. */
       simplifyAttributeValue(value, state)
@@ -130,13 +129,10 @@ private static Optional<Fix> dropRedundantCurlies(AnnotationTree tree, VisitorSt
   }
 
   private static Optional<String> simplifyAttributeValue(ExpressionTree expr, VisitorState state) {
-    if (expr.getKind() != Kind.NEW_ARRAY) {
-      /* There are no curly braces or commas to be dropped here. */
-      return Optional.empty();
-    }
-
-    NewArrayTree array = (NewArrayTree) expr;
-    return simplifySingletonArray(array, state).or(() -> dropTrailingComma(array, state));
+    /* Drop curly braces or commas if possible. */
+    return expr instanceof NewArrayTree newArray
+        ? simplifySingletonArray(newArray, state).or(() -> dropTrailingComma(newArray, state))
+        : Optional.empty();
   }
 
   /** Returns the expression describing the array's sole element, if any. */

error-prone-contrib/src/main/java/tech/picnic/errorprone/bugpatterns/DirectReturn.java

@@ -98,19 +98,17 @@ public Description matchBlock(BlockTree tree, VisitorState state) {
   }
 
   private static Optional<ExpressionTree> tryMatchAssignment(Symbol targetSymbol, Tree tree) {
-    if (tree instanceof ExpressionStatementTree) {
-      return tryMatchAssignment(targetSymbol, ((ExpressionStatementTree) tree).getExpression());
+    if (tree instanceof ExpressionStatementTree expressionStatement) {
+      return tryMatchAssignment(targetSymbol, expressionStatement.getExpression());
     }
 
-    if (tree instanceof AssignmentTree) {
-      AssignmentTree assignment = (AssignmentTree) tree;
+    if (tree instanceof AssignmentTree assignment) {
       return targetSymbol.equals(ASTHelpers.getSymbol(assignment.getVariable()))
           ? Optional.of(assignment.getExpression())
           : Optional.empty();
     }
 
-    if (tree instanceof VariableTree) {
-      VariableTree declaration = (VariableTree) tree;
+    if (tree instanceof VariableTree declaration) {
       return declaration.getModifiers().getAnnotations().isEmpty()
               && targetSymbol.equals(ASTHelpers.getSymbol(declaration))
           ? Optional.ofNullable(declaration.getInitializer())
@@ -148,11 +146,11 @@ private static boolean isIdentifierSymbolReferencedInAssociatedFinallyBlock(
             Streams.stream(state.getPath()).skip(1),
             Streams.stream(state.getPath()),
             (tree, child) -> {
-              if (!(tree instanceof TryTree)) {
+              if (!(tree instanceof TryTree tryTree)) {
                 return null;
               }
 
-              BlockTree finallyBlock = ((TryTree) tree).getFinallyBlock();
+              BlockTree finallyBlock = tryTree.getFinallyBlock();
               return !child.equals(finallyBlock) ? finallyBlock : null;
             })
         .anyMatch(finallyBlock -> referencesIdentifierSymbol(symbol, finallyBlock));

error-prone-contrib/src/main/java/tech/picnic/errorprone/bugpatterns/FormatStringConcatenation.java

@@ -240,8 +240,8 @@ private static class ReplacementArgumentsConstructor
     }
 
     private void appendExpression(Tree tree) {
-      if (tree instanceof LiteralTree) {
-        formatString.append(((LiteralTree) tree).getValue());
+      if (tree instanceof LiteralTree literal) {
+        formatString.append(literal.getValue());
       } else {
         formatString.append(formatSpecifier);
         formatArguments.add(tree);

error-prone-contrib/src/main/java/tech/picnic/errorprone/bugpatterns/IsInstanceLambdaUsage.java

@@ -16,7 +16,6 @@
 import com.google.errorprone.util.ASTHelpers;
 import com.sun.source.tree.InstanceOfTree;
 import com.sun.source.tree.LambdaExpressionTree;
-import com.sun.source.tree.Tree.Kind;
 import com.sun.source.tree.VariableTree;
 import tech.picnic.errorprone.bugpatterns.util.SourceCode;
 
@@ -42,12 +41,12 @@ public IsInstanceLambdaUsage() {}
 
   @Override
   public Description matchLambdaExpression(LambdaExpressionTree tree, VisitorState state) {
-    if (tree.getParameters().size() != 1 || tree.getBody().getKind() != Kind.INSTANCE_OF) {
+    if (tree.getParameters().size() != 1
+        || !(tree.getBody() instanceof InstanceOfTree instanceOf)) {
       return Description.NO_MATCH;
     }
 
     VariableTree param = Iterables.getOnlyElement(tree.getParameters());
-    InstanceOfTree instanceOf = (InstanceOfTree) tree.getBody();
     if (!ASTHelpers.getSymbol(param).equals(ASTHelpers.getSymbol(instanceOf.getExpression()))) {
       return Description.NO_MATCH;
     }

error-prone-contrib/src/main/java/tech/picnic/errorprone/bugpatterns/JUnitValueSource.java

@@ -257,8 +257,8 @@ private static Optional<String> tryExtractValueSourceAttributeValue(
             arguments.stream()
                 .map(
                     arg ->
-                        arg instanceof MethodInvocationTree
-                            ? Iterables.getOnlyElement(((MethodInvocationTree) arg).getArguments())
+                        arg instanceof MethodInvocationTree methodInvocation
+                            ? Iterables.getOnlyElement(methodInvocation.getArguments())
                             : arg)
                 .map(argument -> SourceCode.treeToString(argument, state))
                 .collect(joining(", ")))
@@ -285,11 +285,10 @@ private static <T> Optional<T> getElementIfSingleton(Collection<T> collection) {
   private static Matcher<ExpressionTree> isSingleDimensionArrayCreationWithAllElementsMatching(
       Matcher<? super ExpressionTree> elementMatcher) {
     return (tree, state) -> {
-      if (!(tree instanceof NewArrayTree)) {
+      if (!(tree instanceof NewArrayTree newArray)) {
         return false;
       }
 
-      NewArrayTree newArray = (NewArrayTree) tree;
       return newArray.getDimensions().isEmpty()
           && !newArray.getInitializers().isEmpty()
           && newArray.getInitializers().stream()

error-prone-contrib/src/main/java/tech/picnic/errorprone/bugpatterns/LexicographicalAnnotationAttributeListing.java

@@ -31,7 +31,6 @@
 import com.sun.source.tree.NewArrayTree;
 import com.sun.source.tree.PrimitiveTypeTree;
 import com.sun.source.tree.Tree;
-import com.sun.source.tree.Tree.Kind;
 import com.sun.source.util.TreeScanner;
 import com.sun.tools.javac.code.Symtab;
 import com.sun.tools.javac.code.Type;
@@ -119,13 +118,9 @@ private Optional<Fix> sortArrayElements(AnnotationTree tree, VisitorState state)
   }
 
   private static Optional<NewArrayTree> extractArray(ExpressionTree expr) {
-    if (expr.getKind() == Kind.ASSIGNMENT) {
-      return extractArray(((AssignmentTree) expr).getExpression());
-    }
-
-    return Optional.of(expr)
-        .filter(e -> e.getKind() == Kind.NEW_ARRAY)
-        .map(NewArrayTree.class::cast);
+    return expr instanceof AssignmentTree assignment
+        ? extractArray(assignment.getExpression())
+        : Optional.of(expr).filter(NewArrayTree.class::isInstance).map(NewArrayTree.class::cast);
   }
 
   private static Optional<SuggestedFix.Builder> suggestSorting(
@@ -197,8 +192,8 @@ private static ImmutableList<ImmutableList<String>> getStructure(ExpressionTree
       public @Nullable Void visitLiteral(LiteralTree node, @Nullable Void unused) {
         Object value = ASTHelpers.constValue(node);
         nodes.add(
-            value instanceof String
-                ? STRING_ARGUMENT_SPLITTER.splitToStream((String) value).collect(toImmutableList())
+            value instanceof String str
+                ? STRING_ARGUMENT_SPLITTER.splitToStream(str).collect(toImmutableList())
                 : ImmutableList.of(String.valueOf(value)));
 
         return super.visitLiteral(node, unused);

error-prone-contrib/src/main/java/tech/picnic/errorprone/bugpatterns/MethodReferenceUsage.java

@@ -27,7 +27,6 @@
 import com.sun.source.tree.ParenthesizedTree;
 import com.sun.source.tree.ReturnTree;
 import com.sun.source.tree.Tree;
-import com.sun.source.tree.Tree.Kind;
 import com.sun.source.tree.VariableTree;
 import com.sun.tools.javac.code.Symbol;
 import com.sun.tools.javac.code.Type;
@@ -85,6 +84,7 @@ public Description matchLambdaExpression(LambdaExpressionTree tree, VisitorState
         .orElse(Description.NO_MATCH);
   }
 
+  // XXX: Use switch pattern matching once the targeted JDK supports this.
   private static Optional<SuggestedFix.Builder> constructMethodRef(
       LambdaExpressionTree lambdaExpr, Tree subTree) {
     return switch (subTree.getKind()) {
@@ -114,34 +114,35 @@ private static Optional<SuggestedFix.Builder> constructMethodRef(
         .flatMap(expectedInstance -> constructMethodRef(lambdaExpr, subTree, expectedInstance));
   }
 
-  @SuppressWarnings(
-      "java:S1151" /* Extracting `IDENTIFIER` case block to separate method does not improve readability. */)
+  // XXX: Review whether to use switch pattern matching once the targeted JDK supports this.
   private static Optional<SuggestedFix.Builder> constructMethodRef(
       LambdaExpressionTree lambdaExpr,
       MethodInvocationTree subTree,
       Optional<Name> expectedInstance) {
     ExpressionTree methodSelect = subTree.getMethodSelect();
-    return switch (methodSelect.getKind()) {
-      case IDENTIFIER -> {
-        if (expectedInstance.isPresent()) {
-          /* Direct method call; there is no matching "implicit parameter". */
-          yield Optional.empty();
-        }
-        Symbol sym = ASTHelpers.getSymbol(methodSelect);
-        yield ASTHelpers.isStatic(sym)
-            ? constructFix(lambdaExpr, sym.owner, methodSelect)
-            : constructFix(lambdaExpr, "this", methodSelect);
+
+    if (methodSelect instanceof IdentifierTree) {
+      if (expectedInstance.isPresent()) {
+        /* Direct method call; there is no matching "implicit parameter". */
+        return Optional.empty();
       }
-      case MEMBER_SELECT -> constructMethodRef(
-          lambdaExpr, (MemberSelectTree) methodSelect, expectedInstance);
-      default -> throw new VerifyException(
-          "Unexpected type of expression: " + methodSelect.getKind());
-    };
+
+      Symbol sym = ASTHelpers.getSymbol(methodSelect);
+      return ASTHelpers.isStatic(sym)
+          ? constructFix(lambdaExpr, sym.owner, methodSelect)
+          : constructFix(lambdaExpr, "this", methodSelect);
+    }
+
+    if (methodSelect instanceof MemberSelectTree memberSelect) {
+      return constructMethodRef(lambdaExpr, memberSelect, expectedInstance);
+    }
+
+    throw new VerifyException("Unexpected type of expression: " + methodSelect.getKind());
   }
 
   private static Optional<SuggestedFix.Builder> constructMethodRef(
       LambdaExpressionTree lambdaExpr, MemberSelectTree subTree, Optional<Name> expectedInstance) {
-    if (subTree.getExpression().getKind() != Kind.IDENTIFIER) {
+    if (!(subTree.getExpression() instanceof IdentifierTree identifier)) {
       // XXX: Could be parenthesized. Handle. Also in other classes.
       /*
        * Only suggest a replacement if the method select's expression provably doesn't have
@@ -150,12 +151,12 @@ private static Optional<SuggestedFix.Builder> constructMethodRef(
       return Optional.empty();
     }
 
-    Name lhs = ((IdentifierTree) subTree.getExpression()).getName();
+    Name lhs = identifier.getName();
     if (expectedInstance.isEmpty()) {
       return constructFix(lambdaExpr, lhs, subTree.getIdentifier());
     }
 
-    Type lhsType = ASTHelpers.getType(subTree.getExpression());
+    Type lhsType = ASTHelpers.getType(identifier);
     if (lhsType == null || !expectedInstance.orElseThrow().equals(lhs)) {
       return Optional.empty();
     }
@@ -180,8 +181,8 @@ private static Optional<Optional<Name>> matchArguments(
 
     for (int i = 0; i < args.size(); i++) {
       ExpressionTree arg = args.get(i);
-      if (arg.getKind() != Kind.IDENTIFIER
-          || !((IdentifierTree) arg).getName().equals(expectedArguments.get(i + diff))) {
+      if (!(arg instanceof IdentifierTree identifier)
+          || !identifier.getName().equals(expectedArguments.get(i + diff))) {
         return Optional.empty();
       }
     }

error-prone-contrib/src/main/java/tech/picnic/errorprone/bugpatterns/MissingRefasterAnnotation.java

@@ -47,7 +47,7 @@ public MissingRefasterAnnotation() {}
   public Description matchClass(ClassTree tree, VisitorState state) {
     long methodTypes =
         tree.getMembers().stream()
-            .filter(member -> member.getKind() == Tree.Kind.METHOD)
+            .filter(MethodTree.class::isInstance)
             .map(MethodTree.class::cast)
             .filter(method -> !ASTHelpers.isGeneratedConstructor(method))
             .map(method -> REFASTER_ANNOTATION.matches(method, state))

error-prone-contrib/src/main/java/tech/picnic/errorprone/bugpatterns/MockitoMockClassReference.java

@@ -67,6 +67,7 @@ public Description matchMethodInvocation(MethodInvocationTree tree, VisitorState
     return describeMatch(tree, SuggestedFixes.removeElement(arguments.get(0), arguments, state));
   }
 
+  // XXX: Use switch pattern matching once the targeted JDK supports this.
   private static boolean isTypeDerivableFromContext(MethodInvocationTree tree, VisitorState state) {
     Tree parent = state.getPath().getParentPath().getLeaf();
     return switch (parent.getKind()) {

error-prone-contrib/src/main/java/tech/picnic/errorprone/bugpatterns/PrimitiveComparison.java

@@ -21,6 +21,7 @@
 import com.google.errorprone.matchers.Matcher;
 import com.google.errorprone.util.ASTHelpers;
 import com.sun.source.tree.ExpressionTree;
+import com.sun.source.tree.IdentifierTree;
 import com.sun.source.tree.LambdaExpressionTree;
 import com.sun.source.tree.MemberSelectTree;
 import com.sun.source.tree.MethodInvocationTree;
@@ -146,39 +147,42 @@ private static String getPreferredMethod(Type cmpType, boolean isStatic, Visitor
     return isStatic ? "comparing" : "thenComparing";
   }
 
+  // XXX: Use switch pattern matching once the targeted JDK supports this.
   private static Optional<Type> getPotentiallyBoxedReturnType(ExpressionTree tree) {
-    return switch (tree.getKind()) {
-      case LAMBDA_EXPRESSION -> {
-        /* Return the lambda expression's actual return type. */
-        yield Optional.ofNullable(ASTHelpers.getType(((LambdaExpressionTree) tree).getBody()));
-      }
-      case MEMBER_REFERENCE -> {
-        /* Return the method's declared return type. */
-        // XXX: Very fragile. Do better.
-        Type subType2 = ((JCMemberReference) tree).referentType;
-        yield Optional.of(subType2.getReturnType());
-      }
-      default -> {
-        /* This appears to be a genuine `{,ToInt,ToLong,ToDouble}Function`. */
-        yield Optional.empty();
-      }
-    };
+    if (tree instanceof LambdaExpressionTree lambdaExpression) {
+      /* Return the lambda expression's actual return type. */
+      return Optional.ofNullable(ASTHelpers.getType(lambdaExpression.getBody()));
+    }
+
+    // XXX: The match against a concrete type and reference to one of its fields is fragile. Do
+    // better.
+    if (tree instanceof JCMemberReference memberReference) {
+      /* Return the method's declared return type. */
+      Type subType = memberReference.referentType;
+      return Optional.of(subType.getReturnType());
+    }
+
+    /* This appears to be a genuine `{,ToInt,ToLong,ToDouble}Function`. */
+    return Optional.empty();
   }
 
   private static Fix suggestFix(
       MethodInvocationTree tree, String preferredMethodName, VisitorState state) {
     ExpressionTree expr = tree.getMethodSelect();
-    return switch (expr.getKind()) {
-      case IDENTIFIER -> SuggestedFix.builder()
+
+    if (expr instanceof IdentifierTree) {
+      return SuggestedFix.builder()
           .addStaticImport(Comparator.class.getName() + '.' + preferredMethodName)
           .replace(expr, preferredMethodName)
           .build();
-      case MEMBER_SELECT -> {
-        MemberSelectTree ms = (MemberSelectTree) tree.getMethodSelect();
-        yield SuggestedFix.replace(
-            ms, SourceCode.treeToString(ms.getExpression(), state) + '.' + preferredMethodName);
-      }
-      default -> throw new VerifyException("Unexpected type of expression: " + expr.getKind());
-    };
+    }
+
+    if (expr instanceof MemberSelectTree memberSelect) {
+      return SuggestedFix.replace(
+          memberSelect,
+          SourceCode.treeToString(memberSelect.getExpression(), state) + '.' + preferredMethodName);
+    }
+
+    throw new VerifyException("Unexpected type of expression: " + expr.getKind());
   }
 }