fix(jdk-codemodel): capture type-level generic parameter declarations in reflection path

Author: deer

jdk-codemodel/src/main/java/build/codemodel/jdk/JDKCodeModel.java

@@ -65,6 +65,7 @@
 import build.codemodel.objectoriented.descriptor.FieldDescriptor;
 import build.codemodel.objectoriented.descriptor.ImplementsTypeDescriptor;
 import build.codemodel.objectoriented.descriptor.MethodDescriptor;
+import build.codemodel.objectoriented.descriptor.ParameterizedTypeDescriptor;
 import build.codemodel.objectoriented.naming.MethodName;
 import jakarta.inject.Inject;
 
@@ -407,7 +408,14 @@ private Optional<JDKTypeDescriptor> getJDKTypeDescriptor(final Class<?> classTyp
         // include the Classification
         typeDescriptor.addTrait(getClassification(classModifier));
 
-        // TODO: include the generic parameter declarations on the type itself!
+        // include the generic parameter declarations on the type itself
+        final TypeVariable<?>[] typeParameters = classType.getTypeParameters();
+        if (typeParameters.length > 0) {
+            final var typeVars = Arrays.stream(typeParameters)
+                .map(tp -> (TypeVariableUsage) getTypeUsage(tp))
+                .toList();
+            typeDescriptor.addTrait(ParameterizedTypeDescriptor.of(this, typeVars.stream()));
+        }
 
         // include the ExtendsTypeDescriptor (should a super-class be defined)
         final var superType = classType.getAnnotatedSuperclass();

jdk-codemodel/src/test/java/build/codemodel/jdk/JDKCodeModelTests.java

@@ -6,6 +6,8 @@
 import build.codemodel.foundation.usage.GenericTypeUsage;
 import build.codemodel.foundation.usage.NamedTypeUsage;
 import build.codemodel.foundation.usage.WildcardTypeUsage;
+import build.codemodel.foundation.usage.TypeVariableUsage;
+import build.codemodel.jdk.example.BoundedContainer;
 import build.codemodel.jdk.example.WildcardContainer;
 import build.codemodel.hierarchical.descriptor.HierarchicalTypeDescriptor;
 import build.codemodel.jdk.descriptor.JDKTypeDescriptor;
@@ -20,6 +22,7 @@
 import build.codemodel.objectoriented.descriptor.FieldDescriptor;
 import build.codemodel.objectoriented.descriptor.ImplementsTypeDescriptor;
 import build.codemodel.objectoriented.descriptor.MethodDescriptor;
+import build.codemodel.objectoriented.descriptor.ParameterizedTypeDescriptor;
 import org.junit.jupiter.api.Test;
 
 import static org.assertj.core.api.Assertions.assertThat;
@@ -409,4 +412,37 @@ void shouldDiscoverWildcardBoundsViaReflection() {
         assertThat(unboundedWildcard.upperBound()).isEmpty();
         assertThat(unboundedWildcard.lowerBound()).isEmpty();
     }
+
+    @Test
+    void shouldDiscoverTypeParameterDeclarationViaReflection() {
+        final var codeModel = createCodeModel();
+        final var descriptor = codeModel.getJDKTypeDescriptor(Container.class).orElseThrow();
+
+        assertThat(descriptor.getTrait(ParameterizedTypeDescriptor.class)).isPresent();
+
+        final var typeVars = descriptor.getTrait(ParameterizedTypeDescriptor.class)
+            .orElseThrow()
+            .typeVariables()
+            .toList();
+        assertThat(typeVars).hasSize(1);
+        assertThat(typeVars.getFirst().typeName().name().toString()).isEqualTo("T");
+    }
+
+    @Test
+    void shouldDiscoverBoundedTypeParameterDeclarationViaReflection() {
+        final var codeModel = createCodeModel();
+        final var descriptor = codeModel.getJDKTypeDescriptor(BoundedContainer.class).orElseThrow();
+
+        assertThat(descriptor.getTrait(ParameterizedTypeDescriptor.class)).isPresent();
+
+        final var typeVar = descriptor.getTrait(ParameterizedTypeDescriptor.class)
+            .orElseThrow()
+            .typeVariables()
+            .findFirst()
+            .orElseThrow();
+        assertThat(typeVar).isInstanceOf(TypeVariableUsage.class);
+        assertThat(typeVar.typeName().name().toString()).isEqualTo("T");
+        assertThat(typeVar.upperBound()).isPresent();
+        assertThat(((NamedTypeUsage) typeVar.upperBound().get()).typeName().toString()).contains("Number");
+    }
 }

jdk-codemodel/src/test/java/build/codemodel/jdk/example/BoundedContainer.java

@@ -0,0 +1,31 @@
+package build.codemodel.jdk.example;
+
+/*-
+ * #%L
+ * JDK Code Model
+ * %%
+ * Copyright (C) 2026 Workday, Inc.
+ * %%
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ * #L%
+ */
+
+/**
+ * A container with a bounded type parameter, used for reflection-path generic discovery tests.
+ *
+ * @param <T> the element type, bounded by {@link Number}
+ */
+public class BoundedContainer<T extends Number> {
+
+    public T value;
+}