Skip to content
GitLab
Projects Groups Snippets
  • /
  • Help
    • Help
    • Support
    • Community forum
    • Submit feedback
  • Sign in / Register
  • GHC GHC
  • Project information
    • Project information
    • Activity
    • Labels
    • Members
  • Repository
    • Repository
    • Files
    • Commits
    • Branches
    • Tags
    • Contributors
    • Graph
    • Compare
    • Locked Files
  • Issues 5,249
    • Issues 5,249
    • List
    • Boards
    • Service Desk
    • Milestones
    • Iterations
  • Merge requests 578
    • Merge requests 578
  • CI/CD
    • CI/CD
    • Pipelines
    • Jobs
    • Schedules
    • Test Cases
  • Deployments
    • Deployments
    • Releases
  • Analytics
    • Analytics
    • Value stream
    • CI/CD
    • Code review
    • Insights
    • Issue
    • Repository
  • Wiki
    • Wiki
  • Snippets
    • Snippets
  • Activity
  • Graph
  • Create a new issue
  • Jobs
  • Commits
  • Issue Boards
Collapse sidebar
  • Glasgow Haskell CompilerGlasgow Haskell Compiler
  • GHCGHC
  • Issues
  • #10815
Closed
Open
Issue created Aug 31, 2015 by Richard Eisenberg@raeDeveloper

Need more kind inference in associated type instances

When I say

{-# LANGUAGE DataKinds, PolyKinds, TypeFamilies #-}

module Bug where

import Data.Proxy

class kproxy ~ 'KProxy => C (kproxy :: KProxy k) where
  type F (a :: k)

instance C ('KProxy :: KProxy Bool) where
  type F a = Int

I get

    Type indexes must match class instance head
    Found ‘k’ but expected ‘Bool’
    In the type instance declaration for ‘F’
    In the instance declaration for ‘C (KProxy :: KProxy Bool)’

But the kind of a should really be known to be Bool.

This ticket is broken out from ticket:9063#comment:82569, which was evidently not addressed when fixing that ticket.

Patch coming soon.

Trac metadata
Trac field Value
Version 7.10.2
Type Bug
TypeOfFailure OtherFailure
Priority normal
Resolution Unresolved
Component Compiler (Type checker)
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system
Architecture
To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information
Assignee
Assign to
Time tracking