There are several parts here:
1) Enforce the requirement that dictionary arguments not followed by a required argument are optional.
2) Make dictionaries no longer be distinguishable from nullable types.
3) Disallow dictionaries or unions containing dictionaries inside a nullable type.
4) Force optional dictionaries to have a default value of null so that codegen doesn't have to worry about dealing with
optional arguments that have no default value in the IDL but need to be treated as if they were null.
There are several parts here:
1) Enforce the requirement that dictionary arguments not followed by a required argument are optional.
2) Make dictionaries no longer be distinguishable from nullable types.
3) Disallow dictionaries or unions containing dictionaries inside a nullable type.
4) Force optional dictionaries to have a default value of null so that codegen doesn't have to worry about dealing with
optional arguments that have no default value in the IDL but need to be treated as if they were null.
There are two changes here. One is to pass tracking=True to our parser. This makes it properly track positions
of all productions, not just of lexer tokens. The second is to properly count up our newlines in the lex data,
since the lexer seems to report the line number of the start of the lex data, which is always 1 in our case.