Redesigning the CoffeeScript Compiler

Transcript

1. Redesigning the
   CoffeeScript Compiler
   Michael Ficarra
   

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2. Who is this guy?
   

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3. Who is this guy?
   

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4. Who is this guy?
   

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6. “Tell the audience what you're going to say,
   say it; then tell them what you've said.”
   -- Dale Carnegie
   Here's what you're going to learn:
   ● Tools that are a composition of independent
   operations should make accessible useful,
   standardised intermediate representations
   ● Declarative optimisation and compilation rules can
   be startlingly powerful, terse, and (logically) pure
   ● My project is on track to finish in September
   

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7. Please Ask Questions!
   I'm only interesting when properly seeded.
   

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8. Improved Process
   CS CS
   context
   free
   Preprocessor
   

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9. CS
   context
   free
   Improved Process
   Parser
   CS
   AST
   

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10. Improved Process
    Optimiser
    CS
    AST
    CS
    AST
    

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11. Improved Process
    Compiler
    JS
    AST
    CS
    AST
    

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12. Improved Process
    Code Generator
    JS
    AST
    JS
    

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13. Common Use Cases
    CS
    Preprocessor
    Code Generator
    JS
    Parser
    Compiler
    Optimiser
    

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14. Common Use Cases
    CS Preprocessor
    Parser
    CS
    Code Generator
    (CoffeeScript)
    

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31. ● Preprocessor
    ○ creates context-free CoffeeScript for the parser
    ○ enforces a consistent indentation style
    ○ ensures pairing characters are matched
    ● Parser
    ○ preserves raw parse value for all parses
    ○ preserves line/column source information for all parses
    ○ parses all forms of all constructs supported by the compiler
    ● Optimiser
    ○ tree-walking optimisation infrastructure in place
    ○ plenty of optimisation rules; room for more
    ● Compiler
    ○ tree-walking compilation infrastructure
    ○ compilation rules for all but 5 features
    Project Status: Completed
    

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32. ● Extensibility of compilation/optimisation rules
    ● Better CLI
    ○ more "standard" option parsing
    ○ defaults to stdio
    ○ options for output of each IR
    ○ built-in minification/beautification with graceful degredation
    ● Fixes most of the 78(!) verified, open bugs
    ○ nearly all parsing bugs
    ○ code generation bugs (particularly regarding precedence)
    ● Nice build system (thanks, Myles)
    ● Test suite infrastructure
    ● Code coverage infrastructure
    Project Status: Completed
    

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33. ● General tidying up, marked throughout the code-base
    ● Errors generated by the preprocessor need improvement
    ○ doesn't yet track/report offending line/column numbers
    ○ doesn't include surrounding context in errors
    ○ doesn't remember opening char position when EOF reached
    ● Complete test suite
    ○ already ported over ~50% of jashkenas/coffee-script
    ○ porting process is a little slow, lower priority for now
    Project Status: Needs Some Work
    

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34. ● Source mappings
    ○ Source information is already captured
    ○ Needs to propagate through optimiser/compiler rules
    ○ Starting on this today
    ○ Hope to add this logic in a generalised (DRY) way
    ● Port REPL from jashkenas/coffee-script
    ● Self-host
    ○ Most of the project's source files already supported
    ○ Failings due mostly to too-clever implicit object usage
    ● Allow escodegen to format according to a user-provided spec
    Project Status: Not Yet Started
    

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