Passing an 'invokespecial' MethodHandle to LambdaMetafactory—for example, 'invokespecial Object.toString:()Ljava/lang/String'—causes an internal VerificationError, because the lambda class, a nestmate of the original class, does not have access to use invokespecial on the original class's super methods.

java.lang.InternalError: java.lang.VerifyError: Bad type on operand stack
Exception Details:
  Location:
    MetafactoryArgValidationTest$C$$Lambda$63+0x00000007c0102208.m(LMetafactoryArgValidationTest$C;)Ljava/lang/String; @1: invokespecial
  Reason:
    Type 'MetafactoryArgValidationTest$C' (current frame, stack[0]) is not assignable to 'MetafactoryArgValidationTest$C$$Lambda$63+0x00000007c0102208'
  Current Frame:
    bci: @1
    flags: { }
    locals: { 'MetafactoryArgValidationTest$C$$Lambda$63+0x00000007c0102208', 'MetafactoryArgValidationTest$C' }
    stack: { 'MetafactoryArgValidationTest$C' }
  Bytecode:
    0000000: 2bb7 0010 b0

at java.base/java.lang.invoke.InnerClassLambdaMetafactory.generateInnerClass(InnerClassLambdaMetafactory.java:417)
at java.base/java.lang.invoke.InnerClassLambdaMetafactory.spinInnerClass(InnerClassLambdaMetafactory.java:305)
at java.base/java.lang.invoke.InnerClassLambdaMetafactory.buildCallSite(InnerClassLambdaMetafactory.java:218)
at java.base/java.lang.invoke.LambdaMetafactory.metafactory(LambdaMetafactory.java:328)
at MetafactoryArgValidationTest.mfSucceed(MetafactoryArgValidationTest.java:240)
... 8 more

In practice, this does not arise from Java method references because javac always generates a bridge for a 'super::foo' method reference.