With this, only main.cpp instantiates an arena. Maybe we'll want to split that up more later (e.g., so that the runtime interpreter uses its own arena), but given the intent to have type-checking update the AST, I thought this was a reasonable approach for now in order to avoid ownership complexities.
Fixes#769
Doesn't add much logic, only takes advantage of parser structure for the ordering enforcement.
Note import_nonexistent tests should probably fail, but writing import tests needs a chain of functionality, and I figured I'd just start adding some to validate the syntax (not adding existent imports because that'd require multi-file structure).
We're now one step away from eliminating bare pointers in semantic actions.
There are plenty of other cleanups and modernizations that can be made in the
parser, but the elimination of bare pointers is the one that has the highest
impact for the codebase.
Slowly bringing this into line with Bison's C++ example parser
so we can use strong semantic values for symbols rather than
leaking pointers. First step is to thread a `ParseAndLexContext`
object through the whole syntactic analysis state, like the
example has. In the example, it's called `driver`.
Co-authored-by: Geoff Romer <gromer@google.com>
Jon Meow
Geoff Romer
Dave Abrahams