add parser support for non-finite numbers

[tayloraswift]

No description provided.

[gemini-code-assist]

Summary of Changes

Hello @tayloraswift, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request significantly enhances the JSON parser by introducing explicit support for non-finite numerical values, specifically Not-a-Number (NaN) and positive/negative Infinity. By integrating these values into the AST and implementing dedicated parsing rules, the library can now correctly interpret and represent data formats that extend standard JSON numbers, broadening its utility for various data interchange scenarios.

Highlights

• Extended Number Support: The JSON Abstract Syntax Tree (AST) now supports non-finite numbers by introducing a new numberExtension_ case within the JSON.Node enum.
• New NumberExtension_ Enum: A dedicated NumberExtension_ enum has been added to represent NaN (Not-a-Number) and infinity (positive and negative), providing a structured way to handle these values.
• Parsing Rules Implemented: New parsing rules have been added to the JSONParsing module to correctly identify and parse the string representations of 'NaN', 'inf', and '-inf' into their corresponding NumberExtension_ values.
• Typecast Error Handling: The JSON.TypecastError initializer has been updated to correctly categorize numberExtension_ values as .number when typecasting errors occur, ensuring consistent error reporting.

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[gemini-code-assist]

Code Review

This pull request adds support for parsing non-finite numbers like NaN and inf. The changes are well-structured, adding new parsing rules and integrating them into the existing system. I have a couple of suggestions regarding naming conventions and code clarity to improve maintainability. Specifically, I recommend renaming the new NumberExtension_ type and avoiding the use of self for associated values in switch statements to prevent confusion.