Prevent StackOverflow when analyzing generic type

Closes gh-1323

Author: snicoll

spring-aot/src/main/java/org/springframework/aot/context/bootstrap/generator/infrastructure/ProtectedAccessAnalyzer.java

@@ -23,7 +23,9 @@
 import java.lang.reflect.Modifier;
 import java.lang.reflect.Parameter;
 import java.util.ArrayList;
+import java.util.HashSet;
 import java.util.List;
+import java.util.Set;
 import java.util.function.Function;
 
 import org.springframework.aot.context.bootstrap.generator.bean.descriptor.BeanInstanceDescriptor;
@@ -68,7 +70,7 @@ public ProtectedAccessAnalysis analyze(BeanInstanceDescriptor descriptor) {
 
 	private List<ProtectedElement> analyze(ResolvableType target) {
 		List<ProtectedElement> elements = new ArrayList<>();
-		analyze(target, target, elements);
+		analyze(new HashSet<>(), target, target, elements);
 		return elements;
 	}
 
@@ -103,7 +105,12 @@ private List<ProtectedElement> analyze(Parameter[] parameters, Function<Integer,
 		return protectedElements;
 	}
 
-	private void analyze(ResolvableType rootType, ResolvableType target, List<ProtectedElement> elements) {
+	private void analyze(Set<ResolvableType> seen, ResolvableType rootType, ResolvableType target,
+			List<ProtectedElement> elements) {
+		if (seen.contains(target)) {
+			return;
+		}
+		seen.add(target);
 		// resolve to the actual class as the proxy won't have the same characteristics
 		ResolvableType nonProxyTarget = target.as(ClassUtils.getUserClass(target.toClass()));
 		if (!isAccessible(nonProxyTarget.toClass())) {
@@ -117,7 +124,7 @@ private void analyze(ResolvableType rootType, ResolvableType target, List<Protec
 		}
 		if (nonProxyTarget.hasGenerics()) {
 			for (ResolvableType generic : nonProxyTarget.getGenerics()) {
-				analyze(rootType, generic, elements);
+				analyze(seen, rootType, generic, elements);
 			}
 		}
 	}

spring-aot/src/test/java/org/springframework/aot/context/bootstrap/generator/infrastructure/ProtectedAccessAnalyzerTests.java

@@ -27,6 +27,7 @@
 import org.springframework.aot.context.bootstrap.generator.sample.SimpleConfiguration;
 import org.springframework.aot.context.bootstrap.generator.sample.visibility.ProtectedParameter;
 import org.springframework.aot.context.bootstrap.generator.sample.visibility.PublicFactoryBean;
+import org.springframework.core.ResolvableType;
 import org.springframework.util.ReflectionUtils;
 
 import static org.assertj.core.api.Assertions.assertThat;
@@ -152,6 +153,12 @@ void analyzeWithPackagePrivateGenericArgumentInTargetPackage() {
 				PublicFactoryBean.class.getPackageName()).isAccessible()).isTrue();
 	}
 
+	@Test
+	void analyzeWithRecursiveType() {
+		analyze(BeanInstanceDescriptor.of(ResolvableType.forClassWithGenerics(
+				SelfReference.class, SelfReference.class)).build());
+	}
+
 	private ProtectedAccessAnalysis analyze(BeanInstanceDescriptor descriptor) {
 		return analyze(descriptor, "com.example.public");
 	}
@@ -208,4 +215,13 @@ public String stringBean() {
 
 	}
 
+	static class SelfReference<T extends SelfReference<T>> {
+
+		@SuppressWarnings("unchecked")
+		T getThis() {
+			return (T) this;
+		}
+
+	}
+
 }