StatementSwitchToExpressionSwitch: only trigger on compatible target versions

check_api/src/main/java/com/google/errorprone/util/RuntimeVersion.java

@@ -16,9 +16,16 @@
 
 package com.google.errorprone.util;
 
-/** JDK version string utilities. */
+/**
+ * JDK runtime version utilities.
+ *
+ * <p>These methods are generally used when deciding which method to call reflectively. Bug checkers
+ * that rely on support for specific source code constructs should consult {@link SourceVersion}
+ * instead.
+ *
+ * @see RuntimeVersion
+ */
 public final class RuntimeVersion {
-
   private static final int FEATURE = Runtime.version().feature();
 
   /** Returns true if the current runtime is JDK 12 or newer. */

check_api/src/main/java/com/google/errorprone/util/SourceVersion.java

@@ -0,0 +1,58 @@
+/*
+ * Copyright 2023 The Error Prone Authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.errorprone.util;
+
+import com.google.common.collect.ImmutableMap;
+import com.google.common.collect.Maps;
+import com.sun.tools.javac.code.Source;
+import com.sun.tools.javac.code.Source.Feature;
+import com.sun.tools.javac.util.Context;
+import java.util.Arrays;
+
+/**
+ * JDK source version utilities.
+ *
+ * @see RuntimeVersion
+ */
+public final class SourceVersion {
+  private static final ImmutableMap<String, Feature> KNOWN_FEATURES =
+      Maps.uniqueIndex(Arrays.asList(Feature.values()), Enum::name);
+
+  /** Returns true if the compiler source version level supports switch expressions. */
+  public static boolean supportsSwitchExpressions(Context context) {
+    return supportsFeature("SWITCH_EXPRESSION", context);
+  }
+
+  /** Returns true if the compiler source version level supports text blocks. */
+  public static boolean supportsTextBlocks(Context context) {
+    return supportsFeature("TEXT_BLOCKS", context);
+  }
+
+  /**
+   * Returns true if the compiler source version level supports the {@link Feature} indicated by the
+   * specified string.
+   *
+   * @apiNote For features explicitly recognized by this class, prefer calling the associated method
+   *     instead.
+   */
+  public static boolean supportsFeature(String featureString, Context context) {
+    Feature feature = KNOWN_FEATURES.get(featureString);
+    return feature != null && feature.allowedInSource(Source.instance(context));
+  }
+
+  private SourceVersion() {}
+}

core/src/main/java/com/google/errorprone/bugpatterns/StatementSwitchToExpressionSwitch.java

@@ -39,6 +39,7 @@
 import com.google.errorprone.matchers.Description;
 import com.google.errorprone.util.Reachability;
 import com.google.errorprone.util.RuntimeVersion;
+import com.google.errorprone.util.SourceVersion;
 import com.sun.source.tree.BreakTree;
 import com.sun.source.tree.CaseTree;
 import com.sun.source.tree.ExpressionTree;
@@ -85,8 +86,7 @@ public StatementSwitchToExpressionSwitch(ErrorProneFlags flags) {
 
   @Override
   public Description matchSwitch(SwitchTree switchTree, VisitorState state) {
-    // Expression switches finalized in Java 14
-    if (!RuntimeVersion.isAtLeast14()) {
+    if (!SourceVersion.supportsSwitchExpressions(state.context)) {
       return NO_MATCH;
     }