Add failing test for #1868, related

src/main/java/com/fasterxml/jackson/databind/deser/BasicDeserializerFactory.java

@@ -267,7 +267,7 @@ public ValueInstantiator findValueInstantiator(DeserializationContext ctxt,
             }
         }
 
-        // Sanity check: does the chosen instantatior have incomplete creators?
+        // Sanity check: does the chosen ValueInstantiator have incomplete creators?
         if (instantiator.getIncompleteParameter() != null) {
             final AnnotatedParameter nonAnnotatedParam = instantiator.getIncompleteParameter();
             final AnnotatedWithParams ctor = nonAnnotatedParam.getOwner();
@@ -281,7 +281,8 @@ private ValueInstantiator _findStdValueInstantiator(DeserializationConfig config
             BeanDescription beanDesc)
         throws JsonMappingException
     {
-        if (beanDesc.getBeanClass() == JsonLocation.class) {
+        Class<?> raw = beanDesc.getBeanClass();
+        if (raw == JsonLocation.class) {
             return new JsonLocationInstantiator();
         }
         return null;

src/test/java/com/fasterxml/jackson/failing/TestDefaultForUtilCollections1868.java

@@ -0,0 +1,100 @@
+package com.fasterxml.jackson.failing;
+
+import java.util.*;
+
+import com.fasterxml.jackson.annotation.JsonTypeInfo;
+import com.fasterxml.jackson.databind.BaseMapTest;
+import com.fasterxml.jackson.databind.ObjectMapper;
+
+// Unit tests for [databind#1868], related
+public class TestDefaultForUtilCollections1868 extends BaseMapTest
+{
+   private final ObjectMapper DEFAULT_MAPPER = new ObjectMapper();
+   {
+       DEFAULT_MAPPER.enableDefaultTyping(ObjectMapper.DefaultTyping.NON_FINAL, JsonTypeInfo.As.PROPERTY);
+   }
+
+   /*
+   /**********************************************************
+   /* Unit tests, "empty" types
+   /**********************************************************
+    */
+
+   public void testEmptyList() throws Exception {
+       _verifyCollection(Collections.emptyList());
+   }
+
+   public void testEmptySet() throws Exception {
+       _verifyCollection(Collections.emptySet());
+   }
+
+   public void testEmptyMap() throws Exception {
+       _verifyMap(Collections.emptyMap());
+   }
+
+   /*
+   /**********************************************************
+   /* Unit tests, "singleton" types
+   /**********************************************************
+    */
+
+   public void testSingletonList() throws Exception {
+       _verifyCollection(Collections.singletonList(Arrays.asList("TheOne")));
+   }
+
+   public void testSingletonSet() throws Exception {
+       _verifyCollection(Collections.singleton(Arrays.asList("TheOne")));
+   }
+
+   public void testSingletonMap() throws Exception {
+       _verifyMap(Collections.singletonMap("foo", "bar"));
+   }
+
+   /*
+   /**********************************************************
+   /* Unit tests, "unmodifiable" types
+   /**********************************************************
+    */
+
+   public void testUnmodifiableList() throws Exception {
+       _verifyCollection(Collections.unmodifiableList(Arrays.asList("first", "second")));
+   }
+
+   public void testUnmodifiableSet() throws Exception
+   {
+       Set<String> input = new LinkedHashSet<>(Arrays.asList("first", "second"));
+       _verifyCollection(Collections.unmodifiableSet(input));
+   }
+
+   public void testUnmodifiableMap() throws Exception
+   {
+       Map<String,String> input = new LinkedHashMap<>();
+       input.put("a", "b");
+       input.put("c", "d");
+       _verifyMap(Collections.unmodifiableMap(input));
+   }
+
+   /*
+   /**********************************************************
+   /* Helper methods
+   /**********************************************************
+    */
+
+   protected void _verifyCollection(Collection<?> exp) throws Exception
+   {
+       String json = DEFAULT_MAPPER.writeValueAsString(exp);
+       Collection<?> act = DEFAULT_MAPPER.readValue(json, Collection.class);
+
+       assertEquals(exp, act);
+       assertEquals(exp.getClass(), act.getClass());
+   }
+
+   protected void _verifyMap(Map<?,?> exp) throws Exception
+   {
+       String json = DEFAULT_MAPPER.writeValueAsString(exp);
+       Map<?,?> act = DEFAULT_MAPPER.readValue(json, Map.class);
+
+       assertEquals(exp, act);
+       assertEquals(exp.getClass(), act.getClass());
+   }
+}