Add some notes on how feedback-dragging will work
initial code_change.ca
Fix tests. Add Map.modify and Map.list_append
add Stack.get_context
in stack/frames, rename "context" to "env"
VM hacks are now saved in a list. Add Stack.append_hack
move tests/hackset -> tests/hacks
:set_value hacks are now working
initial work on stack_extract_current_path
add _extract_stack_path func
vm :watch
add Stack.copy
test cleanup, add tests/hacks/derivative_test.ca
fix a bug, bad bytecode when :set_value changes type
fix type inferrence for Type.cast. Also don't specialize outputs with explicit type
Fix implicit output types to consider return statements

Also do housecleaning on type inference
no longer allow 'null' as an output for any function. Hooray
minor cleanup in interpreter.cpp
More type inferrence. In PopOutput, only cast if needed
add first_frame, next_frame. Preparing for Stack refactor