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DisambiguateRecordFields fails for PatternSynonyms

    • Closed Issue created by Adam Gundry @adamgundry

    Consider:

    {-# LANGUAGE PatternSynonyms #-}

module A where

pattern S{x} = [x]
    {-# LANGUAGE PatternSynonyms, DisambiguateRecordFields #-}

module B where

import A

pattern T{x} = [x]

e = S { x = 42 }

    Compiling module B fails with Ambiguous occurrence ‘x’ in the definition of e. In principle, DisambiguateRecordFields should select the field belonging to the S "data constructor". However, the current implementation of this works by identifying the parent type constructor, which doesn't exist for a pattern synonym.

    This continues to fail if T is replaced by a data type with a field x. If S is replaced by a data type, however, it starts working.

    Trac metadata
    Trac field Value
    Version 8.2.1
    Type Bug
    TypeOfFailure OtherFailure
    Priority normal
    Resolution Unresolved
    Component Compiler (Type checker)
    Test case
    Differential revisions
    BlockedBy
    Related #11283 (closed)
    Blocking
    CC mpickering
    Operating system
    Architecture
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