Skip to content

GitLab

  • Menu
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 4,867
    • Issues 4,867
    • List
    • Boards
    • Service Desk
    • Milestones
    • Iterations
  • Merge requests 457
    • Merge requests 457
  • 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 Compiler
  • GHCGHC
  • Issues
  • #3696
Closed
Open
Created Nov 26, 2009 by spl@trac-spl

Incorrect type inferred with -fwarn-missing-signatures and a type class

The inferred type using -fwarn-missing-signatures and a type class is too general for top-level values.

Here is a simplified example:

{-# OPTIONS -Wall #-}

class C a where c :: a

instance C Int where c = 37

def = c

use :: Int
use = def

The inferred type reported by GHCi when -fwarn-missing-signatures is enabled is:

Ex.hs:7:0:
    Warning: Definition but no type signature for `def'
             Inferred type: def :: a

The most general possible type here is C a => a. When asking GHCi for the type of def, it reports Int.

Trac metadata
Trac field Value
Version 6.10.1
Type Bug
TypeOfFailure OtherFailure
Priority normal
Resolution Unresolved
Component Compiler (Type checker)
Test case
Differential revisions
BlockedBy
Related
Blocking
CC leather@cs.uu.nl
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