Polish 'Handle generics with identical names in different positions'

See gh-45011

Author: philwebb

spring-boot-project/spring-boot-tools/spring-boot-configuration-processor/src/main/java/org/springframework/boot/configurationprocessor/TypeUtils.java

@@ -46,6 +46,7 @@
  * @author Stephane Nicoll
  * @author Phillip Webb
  * @author Pavel Anisimov
+ * @author Dmytro Nosan
  */
 class TypeUtils {
 
@@ -217,7 +218,7 @@ private TypeKind getPrimitiveFor(TypeMirror type) {
 		return WRAPPER_TO_PRIMITIVE.get(type.toString());
 	}
 
-	TypeDescriptor resolveTypeDescriptor(TypeElement element) {
+	private TypeDescriptor resolveTypeDescriptor(TypeElement element) {
 		if (this.typeDescriptors.containsKey(element)) {
 			return this.typeDescriptors.get(element);
 		}
@@ -318,22 +319,22 @@ private String determineQualifiedName(DeclaredType type, TypeElement enclosingEl
 		}
 
 		@Override
-		public String visitTypeVariable(TypeVariable t, TypeDescriptor descriptor) {
-			TypeMirror typeMirror = descriptor.resolveGeneric(t);
-			if (typeMirror != null) {
-				if (typeMirror instanceof TypeVariable typeVariable) {
+		public String visitTypeVariable(TypeVariable typeVariable, TypeDescriptor descriptor) {
+			TypeMirror resolvedGeneric = descriptor.resolveGeneric(typeVariable);
+			if (resolvedGeneric != null) {
+				if (resolvedGeneric instanceof TypeVariable resolveTypeVariable) {
 					// Still unresolved, let's use the upper bound, checking first if
 					// a cycle may exist
-					if (!hasCycle(typeVariable)) {
-						return visit(typeVariable.getUpperBound(), descriptor);
+					if (!hasCycle(resolveTypeVariable)) {
+						return visit(resolveTypeVariable.getUpperBound(), descriptor);
 					}
 				}
 				else {
-					return visit(typeMirror, descriptor);
+					return visit(resolvedGeneric, descriptor);
 				}
 			}
 			// Fallback to simple representation of the upper bound
-			return defaultAction(t.getUpperBound(), descriptor);
+			return defaultAction(typeVariable.getUpperBound(), descriptor);
 		}
 
 		private boolean hasCycle(TypeVariable variable) {
@@ -394,20 +395,11 @@ static class TypeDescriptor {
 		private final Map<TypeVariable, TypeMirror> generics = new HashMap<>();
 
 		TypeMirror resolveGeneric(TypeVariable typeVariable) {
-			if (this.generics.containsKey(typeVariable)) {
-				TypeMirror resolvedType = this.generics.get(typeVariable);
-				// Unresolved <T> -> <T>
-				if (resolvedType == typeVariable) {
-					return resolvedType;
-				}
-				// <T> -> <T1> -> <T2>
-				if (resolvedType instanceof TypeVariable) {
-					return resolveGeneric((TypeVariable) resolvedType);
-				}
-				// Resolved e.g. java.lang.String
-				return resolvedType;
+			TypeMirror resolved = this.generics.get(typeVariable);
+			if (resolved != typeVariable && resolved instanceof TypeVariable resolvedTypeVariable) {
+				return resolveGeneric(resolvedTypeVariable);
 			}
-			return null;
+			return resolved;
 		}
 
 		private void registerIfNecessary(TypeMirror variable, TypeMirror resolution) {

spring-boot-project/spring-boot-tools/spring-boot-configuration-processor/src/test/java/org/springframework/boot/configurationprocessor/TypeUtilsTests.java

@@ -54,7 +54,6 @@ void resolveTypeOnConcreteClass() {
 			assertThat(getTypeOfField(typeUtils, typeElement, "name")).hasToString(String.class.getName());
 			assertThat(getTypeOfField(typeUtils, typeElement, "mappings"))
 				.hasToString(constructMapType(Integer.class, Duration.class));
-
 		});
 	}