Reject @Bean method with void return type

Closes gh-31007

spring-context/src/test/java/org/springframework/context/annotation/configuration/ConfigurationClassProcessingTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2022 the original author or authors.
+ * Copyright 2002-2023 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -143,6 +143,12 @@ class ConfigurationClassProcessingTests {
 				initBeanFactory(ConfigWithFinalBean.class));
 	}
 
+	@Test  // gh-31007
+	void voidBeanMethod() {
+		assertThatExceptionOfType(BeanDefinitionParsingException.class).isThrownBy(() ->
+				initBeanFactory(ConfigWithVoidBean.class));
+	}
+
 	@Test
 	void simplestPossibleConfig() {
 		BeanFactory factory = initBeanFactory(SimplestPossibleConfig.class);
@@ -432,6 +438,14 @@ class ConfigurationClassProcessingTests {
 	}
 
 
+	@Configuration
+	static class ConfigWithVoidBean {
+
+		public @Bean void testBean() {
+		}
+	}
+
+
 	@Configuration
 	static class SimplestPossibleConfig {