Add failing test for wildcard generic type resolution (#5285)

src/test/java/com/fasterxml/jackson/databind/type/WildcardGenericType5285Test.java

@@ -0,0 +1,129 @@
+package com.fasterxml.jackson.databind.type;
+
+import com.fasterxml.jackson.annotation.JsonSubTypes;
+import com.fasterxml.jackson.annotation.JsonTypeInfo;
+import com.fasterxml.jackson.annotation.JsonTypeInfo.Id;
+import com.fasterxml.jackson.databind.JavaType;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.testutil.DatabindTestUtil;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+/**
+ * Test for issue #5285: Wildcard generic type resolution should respect type bounds
+ */
+public class WildcardGenericType5285Test extends DatabindTestUtil
+{
+    // Generic wrapper class with bounded type parameter
+    public static class MessageWrapper<T extends Settings> {
+        public T settings;
+        public String message;
+
+        public MessageWrapper() { }
+
+        public MessageWrapper(T settings, String message) {
+            this.settings = settings;
+            this.message = message;
+        }
+
+        public T getSettings() { return settings; }
+        public void setSettings(T settings) { this.settings = settings; }
+
+        public String getMessage() { return message; }
+        public void setMessage(String message) { this.message = message; }
+    }
+
+    // Settings interface with polymorphic type info
+    @JsonTypeInfo(use = Id.NAME, property = "type")
+    @JsonSubTypes({
+        @JsonSubTypes.Type(value = EmailSettings.class, name = "EMAIL"),
+        @JsonSubTypes.Type(value = PhoneSettings.class, name = "PHONE")
+    })
+    public interface Settings { }
+
+    public static class EmailSettings implements Settings {
+        public String email;
+
+        public EmailSettings() { }
+
+        public EmailSettings(String email) {
+            this.email = email;
+        }
+
+        public String getEmail() { return email; }
+        public void setEmail(String email) { this.email = email; }
+    }
+
+    public static class PhoneSettings implements Settings {
+        public String phoneNumber;
+
+        public PhoneSettings() { }
+
+        public PhoneSettings(String phoneNumber) {
+            this.phoneNumber = phoneNumber;
+        }
+
+        public String getPhoneNumber() { return phoneNumber; }
+        public void setPhoneNumber(String phoneNumber) { this.phoneNumber = phoneNumber; }
+    }
+
+    // Test wrapper classes
+    static class WildcardWrapper {
+        public MessageWrapper<?> wildcardWrapper;
+    }
+
+    static class SpecificWrapper {
+        public MessageWrapper<EmailSettings> specificWrapper;
+    }
+
+    @Test
+    public void testWildcardTypeResolution() throws Exception
+    {
+        ObjectMapper mapper = newJsonMapper();
+
+        // Create identical instances
+        EmailSettings emailSettings = new EmailSettings("me@me.com");
+        MessageWrapper<EmailSettings> wrapper = new MessageWrapper<>(emailSettings, "Sample Message");
+
+        WildcardWrapper wildcardObj = new WildcardWrapper();
+        wildcardObj.wildcardWrapper = wrapper;
+
+        SpecificWrapper specificObj = new SpecificWrapper();
+        specificObj.specificWrapper = wrapper;
+
+        // Get the JavaType for both field declarations
+        JavaType wildcardFieldType = mapper.getTypeFactory().constructType(
+            WildcardWrapper.class.getDeclaredField("wildcardWrapper").getGenericType());
+        JavaType specificFieldType = mapper.getTypeFactory().constructType(
+            SpecificWrapper.class.getDeclaredField("specificWrapper").getGenericType());
+
+        System.out.println("Wildcard field type: " + wildcardFieldType);
+        System.out.println("Specific field type: " + specificFieldType);
+
+        // Serialize both
+        String wildcardJson = mapper.writeValueAsString(wildcardObj);
+        String specificJson = mapper.writeValueAsString(specificObj);
+
+        System.out.println("Wildcard JSON: " + wildcardJson);
+        System.out.println("Specific JSON: " + specificJson);
+
+        // The wildcard version should also include the "type" field for polymorphic serialization
+        assertTrue(wildcardJson.contains("\"type\":\"EMAIL\""),
+            "Wildcard wrapper should include type field for polymorphic serialization");
+
+        // Both should produce equivalent JSON (modulo field names)
+        assertTrue(specificJson.contains("\"type\":\"EMAIL\""),
+            "Specific wrapper should include type field");
+
+        // The type parameter should resolve to Settings, not Object
+        JavaType contentType = wildcardFieldType.containedType(0);
+        System.out.println("Wildcard content type: " + contentType);
+
+        // Should be Settings or a subtype, not Object
+        assertTrue(Settings.class.isAssignableFrom(contentType.getRawClass()) ||
+                   contentType.getRawClass().equals(Settings.class),
+            "Wildcard type parameter should resolve to Settings bound, not Object. Got: " + contentType);
+    }
+}