Add ModuleSerializationProxy.java to avoid MissingRequirementError

We should probably make the compiler tolerant to the absense of this
class, but I'll add it here in the meantime.

Author: retronym

corpus/scala/21d12e9/library/scala/runtime/ModuleSerializationProxy.java

@@ -0,0 +1,51 @@
+/*
+ * Scala (https://www.scala-lang.org)
+ *
+ * Copyright EPFL and Lightbend, Inc.
+ *
+ * Licensed under Apache License 2.0
+ * (http://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package scala.runtime;
+
+import java.io.Serializable;
+import java.security.AccessController;
+import java.security.PrivilegedActionException;
+import java.security.PrivilegedExceptionAction;
+import java.util.HashSet;
+import java.util.Set;
+
+/** A serialization proxy for singleton objects */
+public final class ModuleSerializationProxy implements Serializable {
+    private static final long serialVersionUID = 1L;
+    private final Class<?> moduleClass;
+    private static final ClassValue<Object> instances = new ClassValue<Object>() {
+        @Override
+        protected Object computeValue(Class<?> type) {
+            try {
+                return AccessController.doPrivileged((PrivilegedExceptionAction<Object>) () -> type.getField("MODULE$").get(null));
+            } catch (PrivilegedActionException e) {
+                return rethrowRuntime(e.getCause());
+            }
+        }
+    };
+
+    private static Object rethrowRuntime(Throwable e) {
+        Throwable cause = e.getCause();
+        if (cause instanceof RuntimeException) throw (RuntimeException) cause;
+        else throw new RuntimeException(cause);
+    }
+
+    public ModuleSerializationProxy(Class<?> moduleClass) {
+        this.moduleClass = moduleClass;
+    }
+
+    @SuppressWarnings("unused")
+    private Object readResolve() {
+        return instances.get(moduleClass);
+    }
+}