B-Lang-org/bsc

Better error message for -> instead of => in type signature

Open

#337 opened on Mar 19, 2021

View on GitHub
 (3 comments) (0 reactions) (0 assignees)Haskell (178 forks)batch import
good first issue

Repository metrics

Stars
 (1,108 stars)
PR merge metrics
 (Avg merge 17d 1h) (18 merged PRs in 30d)

Description

We've seen all sorts of hilarity including things like:

Type error at: d

Expected type: t

Inferred type: (Prelude.IsModule m mType, Prelude.Bits t st) (ironically one of the easier-to-diagnose variants).

I suspect some sort of up-front check that classes aren't where they aren't supposed to be in a type signature would help here. Add comment

Contributor guide

Research direction
Look at the parser or type checker to detect when ` >` is used instead of `=>` in type signatures and add a specific error message.
Tech stack
haskell
Domain
compilers
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Fresh
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
Haskellcompiler basics
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
65