Fix a regression in Kotlin serialization support

After gh-29068, some Type instances can throw an
IllegalArgumentException. This commit catches them
properly to just return a null serializer in that
case.

Closes gh-29192

spring-web/src/main/java/org/springframework/http/codec/json/KotlinSerializationJsonDecoder.java

@@ -133,7 +133,11 @@ public class KotlinSerializationJsonDecoder extends AbstractDecoder<Object> {
 	private KSerializer<Object> serializer(Type type) {
 		KSerializer<Object> serializer = serializerCache.get(type);
 		if (serializer == null) {
-			serializer = SerializersKt.serializerOrNull(type);
+			try {
+				serializer = SerializersKt.serializerOrNull(type);
+			}
+			catch (IllegalArgumentException ignored) {
+			}
 			if (serializer == null || hasPolymorphism(serializer.getDescriptor(), new HashSet<>())) {
 				return null;
 			}

spring-web/src/main/java/org/springframework/http/codec/json/KotlinSerializationJsonEncoder.java

@@ -121,7 +121,11 @@ public class KotlinSerializationJsonEncoder extends AbstractEncoder<Object> {
 	private KSerializer<Object> serializer(Type type) {
 		KSerializer<Object> serializer = serializerCache.get(type);
 		if (serializer == null) {
-			serializer = SerializersKt.serializerOrNull(type);
+			try {
+				serializer = SerializersKt.serializerOrNull(type);
+			}
+			catch (IllegalArgumentException ignored) {
+			}
 			if (serializer == null || hasPolymorphism(serializer.getDescriptor(), new HashSet<>())) {
 				return null;
 			}

spring-web/src/main/java/org/springframework/http/converter/json/KotlinSerializationJsonHttpMessageConverter.java

@@ -173,7 +173,11 @@ public class KotlinSerializationJsonHttpMessageConverter extends AbstractGeneric
 	private KSerializer<Object> serializer(Type type) {
 		KSerializer<Object> serializer = serializerCache.get(type);
 		if (serializer == null) {
-			serializer = SerializersKt.serializerOrNull(type);
+			try {
+				serializer = SerializersKt.serializerOrNull(type);
+			}
+			catch (IllegalArgumentException ignored) {
+			}
 			if (serializer == null || hasPolymorphism(serializer.getDescriptor(), new HashSet<>())) {
 				return null;
 			}

spring-web/src/test/kotlin/org/springframework/http/codec/json/KotlinSerializationJsonDecoderTests.kt

@@ -61,6 +61,7 @@ class KotlinSerializationJsonDecoderTests : AbstractDecoderTests<KotlinSerializa
 		Assertions.assertThat(decoder.canDecode(ResolvableType.forClassWithGenerics(ArrayList::class.java, Int::class.java), MediaType.APPLICATION_JSON)).isTrue()
 		Assertions.assertThat(decoder.canDecode(ResolvableType.forClassWithGenerics(ArrayList::class.java, Int::class.java), MediaType.APPLICATION_PDF)).isFalse()
 		Assertions.assertThat(decoder.canDecode(ResolvableType.forClass(Ordered::class.java), MediaType.APPLICATION_JSON)).isFalse()
+		Assertions.assertThat(decoder.canDecode(ResolvableType.NONE, MediaType.APPLICATION_JSON)).isFalse()
 	}
 
 	@Test

spring-web/src/test/kotlin/org/springframework/http/codec/json/KotlinSerializationJsonEncoderTests.kt

@@ -56,6 +56,7 @@ class KotlinSerializationJsonEncoderTests : AbstractEncoderTests<KotlinSerializa
 		Assertions.assertThat(encoder.canEncode(ResolvableType.forClassWithGenerics(List::class.java, Pojo::class.java), MediaType.APPLICATION_JSON)).isTrue()
 		Assertions.assertThat(encoder.canEncode(ResolvableType.forClassWithGenerics(ArrayList::class.java, Int::class.java), MediaType.APPLICATION_JSON)).isTrue()
 		Assertions.assertThat(encoder.canEncode(ResolvableType.forClassWithGenerics(ArrayList::class.java, Int::class.java), MediaType.APPLICATION_PDF)).isFalse()
+		Assertions.assertThat(encoder.canEncode(ResolvableType.NONE, MediaType.APPLICATION_JSON)).isFalse()
 	}
 
 	@Test

spring-web/src/test/kotlin/org/springframework/http/converter/json/KotlinSerializationJsonHttpMessageConverterTests.kt

@@ -21,6 +21,7 @@ import org.assertj.core.api.Assertions.assertThat
 import org.assertj.core.api.Assertions.assertThatExceptionOfType
 import org.junit.jupiter.api.Test
 import org.springframework.core.Ordered
+import org.springframework.core.ResolvableType
 import org.springframework.http.MediaType
 import org.springframework.http.MockHttpInputMessage
 import org.springframework.http.MockHttpOutputMessage
@@ -62,6 +63,8 @@ class KotlinSerializationJsonHttpMessageConverterTests {
 
 		assertThat(converter.canRead(typeTokenOf<Ordered>(), Ordered::class.java, MediaType.APPLICATION_JSON)).isFalse()
 		assertThat(converter.canRead(typeTokenOf<List<Ordered>>(), List::class.java, MediaType.APPLICATION_JSON)).isFalse()
+
+		assertThat(converter.canRead(ResolvableType.NONE.type, null, MediaType.APPLICATION_JSON)).isFalse()
 	}
 
 	@Test
@@ -83,6 +86,8 @@ class KotlinSerializationJsonHttpMessageConverterTests {
 		assertThat(converter.canWrite(typeTokenOf<List<Int>>(), List::class.java, MediaType.APPLICATION_PDF)).isFalse()
 
 		assertThat(converter.canWrite(typeTokenOf<Ordered>(), Ordered::class.java, MediaType.APPLICATION_JSON)).isFalse()
+
+		assertThat(converter.canWrite(ResolvableType.NONE.type, SerializableBean::class.java, MediaType.APPLICATION_JSON)).isFalse()
 	}
 
 	@Test