* Permit %%placeholder%% in left-hand-side of a let declaration
* Test that "let" followed by modulo is still treated as an identifier
* More tests for edge-case handling of "let" with placeholders enabled
* Fix location with optional params in arrow functions
* add test
* Ensure rollup replaces NODE_ENV and create sourcemap in dev
* Ensure finishNod*() is never called twice on a node
* Fix check for already finished nodes
