Fix JDK 20-ea build compatibility

With these changes the JDK 20-ea build on GitHub Actions passes again.

Fixes #3610

FUTURE_COPYBARA_INTEGRATE_REVIEW=#3610 from PicnicSupermarket:bugfix/jdk-20-enhanced-for-loop-compat 0b534d2
PiperOrigin-RevId: 498578771

core/src/main/java/com/google/errorprone/refaster/UEnhancedForLoop.java

@@ -19,6 +19,7 @@
 import static com.google.errorprone.refaster.Unifier.unifications;
 
 import com.google.auto.value.AutoValue;
+import com.google.common.base.VerifyException;
 import com.google.errorprone.util.RuntimeVersion;
 import com.sun.source.tree.EnhancedForLoopTree;
 import com.sun.source.tree.Tree;
@@ -29,6 +30,7 @@
 import com.sun.tools.javac.tree.JCTree.JCStatement;
 import com.sun.tools.javac.tree.JCTree.JCVariableDecl;
 import com.sun.tools.javac.tree.TreeMaker;
+import java.util.Arrays;
 
 /**
  * A {@link UTree} representation of a {@link EnhancedForLoopTree}.
@@ -39,7 +41,63 @@
 abstract class UEnhancedForLoop extends USimpleStatement implements EnhancedForLoopTree {
   public static UEnhancedForLoop create(
       UVariableDecl variable, UExpression elements, UStatement statement) {
-    return new AutoValue_UEnhancedForLoop(variable, elements, (USimpleStatement) statement);
+    // On JDK 20 and above the `EnhancedForLoopTree` interface contains a additional method
+    // `getDeclarationKind()`, referencing a  type not available prior to JDK 20. AutoValue
+    // generates a corresponding field and accessor for this property. Here we find and invoke the
+    // generated constructor with the appropriate arguments, depending on context.
+    // See https://github.com/openjdk/jdk20/commit/2cb64a75578ccc15a1dfc8c2843aa11d05ca8aa7.
+    // TODO: Simplify this logic once JDK 19 and older are no longer supported.
+    return isCompiledWithJdk20Plus()
+        ? createJdk20PlusEnhancedForLoop(variable, elements, statement)
+        : createPreJdk20EnhancedForLoop(variable, elements, statement);
+  }
+
+  private static boolean isCompiledWithJdk20Plus() {
+    return Arrays.stream(AutoValue_UEnhancedForLoop.class.getDeclaredMethods())
+        .anyMatch(m -> "getDeclarationKind".equals(m.getName()));
+  }
+
+  private static UEnhancedForLoop createPreJdk20EnhancedForLoop(
+      UVariableDecl variable, UExpression elements, UStatement statement) {
+    try {
+      return AutoValue_UEnhancedForLoop.class
+          .getDeclaredConstructor(UVariableDecl.class, UExpression.class, USimpleStatement.class)
+          .newInstance(variable, elements, statement);
+    } catch (ReflectiveOperationException e) {
+      throw new LinkageError(e.getMessage(), e);
+    }
+  }
+
+  private static UEnhancedForLoop createJdk20PlusEnhancedForLoop(
+      UVariableDecl variable, UExpression elements, UStatement statement) {
+    Object declarationKind = getVariableDeclarationKind();
+    try {
+      return AutoValue_UEnhancedForLoop.class
+          .getDeclaredConstructor(
+              declarationKind.getClass(),
+              UVariableDecl.class,
+              UExpression.class,
+              USimpleStatement.class)
+          .newInstance(declarationKind, variable, elements, statement);
+    } catch (ReflectiveOperationException e) {
+      throw new LinkageError(e.getMessage(), e);
+    }
+  }
+
+  private static Object getVariableDeclarationKind() {
+    Class<?> declarationKind;
+    try {
+      declarationKind = Class.forName("com.sun.source.tree.EnhancedForLoopTree$DeclarationKind");
+    } catch (ClassNotFoundException e) {
+      throw new VerifyException("Cannot load `EnhancedForLoopTree.DeclarationKind` enum", e);
+    }
+    return Arrays.stream(declarationKind.getEnumConstants())
+        .filter(v -> "VARIABLE".equals(v.toString()))
+        .findFirst()
+        .orElseThrow(
+            () ->
+                new VerifyException(
+                    "Enum value `EnhancedForLoopTree.DeclarationKind.VARIABLE` not found"));
   }
 
   @Override

pom.xml

@@ -159,6 +159,7 @@
           <target>11</target>
           <parameters />
           <compilerArgs>
+            <arg>--add-exports=java.base/jdk.internal.javac=ALL-UNNAMED</arg>
             <arg>--add-exports=jdk.compiler/com.sun.tools.javac.api=ALL-UNNAMED</arg>
             <arg>--add-exports=jdk.compiler/com.sun.tools.javac.file=ALL-UNNAMED</arg>
             <arg>--add-exports=jdk.compiler/com.sun.tools.javac.code=ALL-UNNAMED</arg>