I knew I should have taken that left turn at Albequirky

rabbithole.txt

So this is why I get lost in NQP/MoarVM.

Objective: figure out how to create a non-resumable subclass of Exception

Step 1: Look at Exception, notice "method resumable" checks $!ex at key 'resume' and "method resume" just calls nqp::resume
Step 2: Well, I could just override those, but what if the nqp op is called directly somewhere.  Better investigate
Step 3: OK $!ex is made by calling "nqp::newexception". rgrep nqp tree for it
step 4: OK that's mapped to MoarVM "newexeception" op.  Resist the urge to say "this goes to VM level too?!?"
        since exceptions are pretty low level VM things. and I knew that would happen in this case.
Step 5: Look at NQP and MoarVM exception pods.  Don't find anything about default init values or instatiation params there.
Step 6: grep for newexception.  Note that it is specialized.  Wonder how MVM_OP_sp_fastcreate works, decide
        to put a pin in worrying about this codepath and lok at the interpreted one first.
Step 7: OK op newexception just finds boot_types.BOOTException and uses a generic initializer on it. Look for that.
Step 8: rest eyes.  starting to glaze.
Step 9: Ok I guess that BootException just maps to MVM_REPR_ID_MVMException.  Which is just 22.
Step 10: Figure out that that maps to a C type MVMException.
Step 11: OK, that has two null-if-not-resumable address pointers, one for jit jit_resume_label and one
         for unjitted resume_addr.  No C code that would implement a .resume that checks resumability.
Step 12: Wait what, where is $!ex.resume?  Did we miss it in nqp? how does that become an nqp attribute?
Step 13: Find MVM_REPR_DEFAULT_GET_ATTRIBUTE, it's a die.
Step 14: Try:

$ perl6 -e 'Exception.new().resumable.say'
This type does not support associative operations
  in block <unit> at -e line 1

Step 15: Well hell. I'm going to bed.