Because the parser conversion functions may not understand their current
position in the code, we instead need to construct a `ParserSyntaxError`
without the current line and column information, filling it in later.
Originally I did this by allowing ParserSyntaxError to be partially
initialized, but this wasn't very type-safe, and required some ugly
assertions.
Instead, I now construct and raise a PartialParserSyntaxError. The
BaseParser class is responsible for catching that partial error object
and constructing a full ParserSyntaxError.
For anything that's not an internal logic error, conversion functions
should raise a ParserSyntaxError.
Internal logic errors should probably use an AssertionError or an assert
statement, but that's not as important and is out of scope for this PR.
We pass down the correct default annotation indicator to use in 100% of code rendering places, so this becomes a useless bit of initialization. We already set this to a sentinel by default, and the only thing that having an explicit str gives us is the inability to copy an annotation from a param to a return or vice versa. So, out it goes. This means we can't render Annotation by itself, so the test that was using this behavior is out too.
This finishes the parser! 🎉
A few related changes were made:
- `DummyNode` was removed, as it's no longer needed.
- `lpar`/`rpar` was removed from `StarredDictElement`, because I found
out that it's not valid syntax while developing the parsing logic.
