Clear reflection caches in black box codegen tests

To prevent tests from altering outcomes of the subsequent tests.

Also expose the clearCaches method (in the internal class
ReflectionFactoryImpl) so that it can be used in other places in similar
circumstances

compiler/tests-common/org/jetbrains/kotlin/codegen/AbstractBlackBoxCodegenTest.java

@@ -26,6 +26,7 @@ import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import org.jetbrains.kotlin.cli.jvm.compiler.KotlinCoreEnvironment;
 import org.jetbrains.kotlin.fileClasses.JvmFileClassUtil;
+import org.jetbrains.kotlin.load.java.JvmAbi;
 import org.jetbrains.kotlin.psi.KtDeclaration;
 import org.jetbrains.kotlin.psi.KtFile;
 import org.jetbrains.kotlin.psi.KtNamedFunction;
@@ -159,6 +160,23 @@ public abstract class AbstractBlackBoxCodegenTest extends CodegenTestCase {
                 System.out.println(generateToText());
                 throw ExceptionUtilsKt.rethrow(e);
             }
+            finally {
+                clearReflectionCache(generatedClassLoader);
+            }
+        }
+    }
+
+    private static void clearReflectionCache(@NotNull ClassLoader classLoader) {
+        try {
+            Class<?> klass = classLoader.loadClass(JvmAbi.REFLECTION_FACTORY_IMPL.asSingleFqName().asString());
+            Method method = klass.getDeclaredMethod("clearCaches");
+            method.invoke(null);
+        }
+        catch (ClassNotFoundException e) {
+            // This is OK for a test without kotlin-reflect in the dependencies
+        }
+        catch (Exception e) {
+            throw ExceptionUtilsKt.rethrow(e);
         }
     }