The ParseTree comments say that preorder is "easier to visualize and read". The problem is, both the ParseTree and Semantics need to operate on the postorder traversal: the ParseTree during construction, and the Semantics during processing. As a consequence, understanding the postorder traversal is important, but it's also very hard to decipher when presented preorder. This PR provides a way to see the postorder, with helpful indents to show subtrees.
This retains the preorder printing as an option for people who prefer that. I'm pretty sure it'll be easier to debug tests if we can see the postorder, so I'm making that the default.
Co-authored-by: Chandler Carruth <chandlerc@gmail.com>
This switch is being done in order to make it easier to update tests when the parse tree structure changes. I've been spending a lot of time doing such updates as part of refactoring the parse tree, and I expect more, so that's really at the root of all the refactoring I've been doing to lit updates.
Jon Ross-PerkinsandChandler Carruth