Skip to content

GitLab

  • Projects
  • Groups
  • Snippets
  • Help
    • Loading...
  • Help
    • Help
    • Support
    • Community forum
    • Submit feedback
  • Sign in / Register
GHC
GHC
  • Project overview
    • Project overview
    • Details
    • Activity
    • Releases
  • Repository
    • Repository
    • Files
    • Commits
    • Branches
    • Tags
    • Contributors
    • Graph
    • Compare
    • Locked Files
  • Issues 4,249
    • Issues 4,249
    • List
    • Boards
    • Labels
    • Service Desk
    • Milestones
    • Iterations
  • Merge Requests 393
    • Merge Requests 393
  • Requirements
    • Requirements
    • List
  • CI / CD
    • CI / CD
    • Pipelines
    • Jobs
    • Schedules
  • Security & Compliance
    • Security & Compliance
    • Dependency List
    • License Compliance
  • Operations
    • Operations
    • Incidents
    • Environments
  • Analytics
    • Analytics
    • CI / CD
    • Code Review
    • Insights
    • Issue
    • Repository
    • Value Stream
  • Wiki
    • Wiki
  • Snippets
    • Snippets
  • Members
    • Members
  • Collapse sidebar
  • Activity
  • Graph
  • Create a new issue
  • Jobs
  • Commits
  • Issue Boards
  • Glasgow Haskell Compiler
  • GHCGHC
  • Issues
  • #16557

Closed
Open
Opened Apr 08, 2019 by Andrew Martin@andrewthadDeveloper

Failing monadic pattern matches have confusing error messages

Motivation

I was just trying to build basement with GHC head (8.9). I got this error message:

Basement/Block/Base.hs:398:9: error:
    Not in scope: ‘fail’
    Perhaps you meant ‘Data.List.tail’ (imported from Data.List)
    |
398 |         arr@(Block arrBa) <- makeTrampoline
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

For those already in the know, it's pretty easy to discern the meaning of this. But for those who aren't, this message is nonsense.

Assignee
Assign to
None
Milestone
None
Assign milestone
Time tracking
None
Due date
None
Reference: ghc/ghc#16557