unisonweb/unison

Pattern matching requires full qualification, construction does not

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#1,272 opened on Feb 25, 2020

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Description

I ran into something I've been able to boil down to this:

type Foo = Bar Nat

bar2 = Bar 2

extractFoo foo = match foo with
  Foo.Bar x -> x

I'm able to construct a Bar without qualifying it as Foo.Bar, but when pattern matching on it, the qualification is required. Without it, I guess this error:

  I don't know about any data constructor named Bar. Maybe make sure it's correctly spelled and
  that you've imported it:
  
      6 |   Bar x -> x

This feels quite inconsistent, and unless I'm overlooking something, I should be able to leave out the Foo qualification in this case.

I'm running the current master, release/M2-base-541-g2adb598e.

Contributor guide

Research direction
Examine the parser rules for constructor patterns and constructor expressions to identify why qualification is required in one and not the other.
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.
Half day
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
Unison
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
60