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  • #9111

Closed
Open
Opened May 14, 2014 by Richard Eisenberg@raeDeveloper

base should export Typeable instances of its promoted data constructors

As initially reported in #8486 (closed), base does not export Typeable instances for its promoted data constructors, as witnessed by this:

{-# LANGUAGE DataKinds #-}

import Data.Typeable

x = typeRep (Proxy :: Proxy True)

yields

    No instance for (Typeable 'True) arising from a use of ‘typeRep’
    In the expression: typeRep (Proxy :: Proxy True)
    In an equation for ‘x’: x = typeRep (Proxy :: Proxy True)

It is indeed possible to derive these instances locally with standalone deriving, but that seems very problematic, should multiple modules do that independently.

Trac metadata
Trac field Value
Version 7.8.2
Type FeatureRequest
TypeOfFailure OtherFailure
Priority normal
Resolution Unresolved
Component Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system
Architecture
Assignee
Assign to
7.10.1
Milestone
7.10.1 (Past due)
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Time tracking
None
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Reference: ghc/ghc#9111