unisonweb/unison

The parser can't handle prefix-patterns based on parenthesized symbolyIds.

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#733 opened on Aug 14, 2019

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Description

use .base

ability Woot where
  (+) : Int -> Int -> Int

wootHandler e = case e of
  {a} -> a
  { (Woot.+) x y -> k } -> 42

So we allow (+) as an ability constructor name, but provide no way of matching on that constructor in the handler.

Workaround for now: either alias the constructor name to something that isn't an operator, or name the ability constructors something else (and provide an operator alias if desired).

We might want more general support for infix patterns too, but I feel like that could use more thought and fixing this seems very doable.

Thanks to @tpolecat for spotting.

Contributor guide

Research direction
Investigate the parser code for handling prefix patterns and symbol IDs, focusing on how parenthesized symbolIds are lexed and parsed in ability handler patterns.
Tech stack
haskell
Domain
backend
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
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Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
HaskellParsing concepts
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
60