A DESCRIPTION OF THE PROBLEM :
When trying to use an unnamed variable as functional interface, the compile reports no error, but I can't run the application.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
java.lang.reflect.InvocationHandler invocationHandler = (_, method, args) -> method.invoke(someObject, args)

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
Working application or compilation error.
ACTUAL -
Compilation works, but the application fails to start with the following error:
Caused by: java.lang.ClassFormatError: Illegal field name "" in class de/porsche/digitalsupport/featureflags/FeatureFlagFactoryBean
at java.base/java.lang.ClassLoader.defineClass(ClassLoader.java:1027)
at java.base/java.security.SecureClassLoader.defineClass(SecureClassLoader.java:150)
at java.base/jdk.internal.loader.BuiltinClassLoader.defineClass(BuiltinClassLoader.java:862)
at java.base/jdk.internal.loader.BuiltinClassLoader.findClassOnClassPathOrNull(BuiltinClassLoader.java:760)
at java.base/jdk.internal.loader.BuiltinClassLoader.loadClassOrNull(BuiltinClassLoader.java:681)
at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:639)
at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:188)
at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:526)
at java.base/java.lang.Class.privateGetDeclaredMethods(Class.java:3578)
at java.base/java.lang.Class.getDeclaredMethods(Class.java:2676)
at org.springframework.util.ReflectionUtils.getDeclaredMethods(ReflectionUtils.java:465)
... 99 more

CUSTOMER SUBMITTED WORKAROUND :
java.lang.reflect.InvocationHandler invocationHandler = (obj, method, args) -> method.invoke(someObject, args)

FREQUENCY : always