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  • Glasgow Haskell CompilerGlasgow Haskell Compiler
  • GHCGHC
  • Issues
  • #14478

Abstract pattern synonyms (for hsig and hs-boot)

Most declaration forms (data types, values, type families, etc) support forward declaration in hs-boot/hsig files. However, pattern synonyms do not. This seems like a major omission!

Some problems to solve:

  • The obvious syntax pattern Foo :: pat_ty is insufficient to specify whether or not a pattern is bidirectional or unidirectional. How should this be represented syntactically?
  • What is the interaction with bundling? Should it be possible to export a bundle of abstract pattern synonyms, with the intent that this means an implementation must also have bundled them together
  • See also #12717; abstract pattern synonym should be implementable with a plain old constructor
Trac metadata
Trac field Value
Version 8.2.1
Type FeatureRequest
TypeOfFailure OtherFailure
Priority normal
Resolution Unresolved
Component Compiler (Type checker)
Test case
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