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Typology is a work in progress attempt to implement type checking of Swift in Swift itself. Currently it uses SwiftSyntax as a parser, but is ready to switch to other pure Swift parsers in the future when any are available.


  • Education: understanding how type checking can be implemented in a Swift compiler
  • User Experience: finding the best way to report type errors and to improve related developer tools
  • Research and Experimentation: prototyping advanced features that could be fully developed within Swift's type system.

How does it work?

Same as the type checker in Apple's Swift compiler, Typology relies on the fact that you can express type systems with a set of constraints on types that are resolved through unification.

See also

Type systems and type checkers

Error reporting

Optimizing type checker's performance for large projects


  • Swift Tools 5.2.0
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Last updated: Wed May 24 2023 11:45:32 GMT-0500 (GMT-05:00)