ucsd-progsys/liquidhaskell

Liquid Haskell should accept `UnicodeSyntax`

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#2,551 opened on Jun 8, 2025

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 (4 comments) (0 reactions) (0 assignees)Haskell (1,306 stars) (157 forks)batch import
good first issue

Description

Setting {-# LANGUAGE UnicodeSyntax #-} in a source file allows us to use, e.g., → and ∷ as -> and ::, but this doesn't apply to Liquid Haskell code, which even with UnicodeSyntax enabled still accepts only the latter. It would be nice if we could use UnicodeSyntax in Liquid Haskell as well.

(Given that we can't at the moment, I've had to abandon UnicodeSyntax for my projects that use Liquid Haskell, as having a mix of the two in the same file makes searching and the like more difficult.)

Contributor guide

Tech stack
None
Domain
developer experiencetooling
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
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
Haskell programmingLiquid Haskell basicsGHC extensions knowledgeParser modification
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
70
Research direction
Investigate how Liquid Haskell currently handles GHC extensions like UnicodeSyntax. Look for existing parser code that converts Unicode tokens to ASCII equivalents. Consider modifying the lexer or parser to accept Unicode characters (→ for >, ∷ for ::) when the UnicodeSyntax extension is enabled. Check for any existing issues or pull requests related to Unicode support.