ucsd-progsys/liquidhaskell

Cannot parse the unit value in refinement bounds

Open

#1,300 opened on Apr 17, 2018

View on GitHub
 (1 comment) (0 reactions) (0 assignees)Haskell (157 forks)batch import
easygood first issueparser

Repository metrics

Stars
 (1,306 stars)
PR merge metrics
 (Avg merge 2d 18h) (12 merged PRs in 30d)

Description

I'm not really sure it's by design or not, LH fails to parse bounds which include the unit literal ().

{-@
    testee :: forall <
                p :: Int -> () -> Int -> Bool
              , q :: Int -> () -> Int -> Bool
              >.
              { n :: Int |- Int<p n ()> <: Int<q n ()> }
              Int
@-}
testee :: Int
testee = 42

Literals of the types other than () look okay, e.g. in the case of Int or Bool, the code is compilable.

{-@
    testee :: forall <
                p :: Int -> Int -> Int -> Bool
              , q :: Int -> Int -> Int -> Bool
              >.
              { n :: Int |- Int<p n 42> <: Int<q n 42> }
              Int
@-}
testee :: Int
testee = 42

Contributor guide

Research direction
Inspect the Haskell source files related to parsing refinement bounds in LiquidHaskell. Look for where unit literal `()` is parsed and compare with how other literals like `42` are handled. The issue likely lies in the parser or type checker for refinement types.
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.
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.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
Haskell
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
70