swiftlang/swift

[SR-8811] Diagnosing Implicit Accessors for Uninhabited Types Should Be Smarter

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#51,319 opened on Sep 20, 2018

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SILcompilerdiagnostics qualitygood first issueimprovement

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Description
Previous ID SR-8811
Radar None
Original Reporter @CodaFi
Type Improvement
Status Reopened
Resolution
Votes 0
Component/s Compiler
Labels Improvement, SILDiagnostics, StarterBug
Assignee None
Priority Medium

md5: fe8546f9296464e8c547c7c953e07a35

Issue Description:

Try to emit SIL for the following code

enum Empty {}

class Foo {
  var x: Empty // function with uninhabited return type 'Empty' is missing call to another never-returning function on all paths

  init(_ x: Empty) {
    self.x = x
  }
}

It's good that we error, it's dismaying that we're diagnosing an implicit declaration. In particular, we're diagnosing the getter. We should check for accessors and emit something specialized here.

Contributor guide

Research direction
Investigate the SILDiagnostics code path for implicit getter accessors of properties with uninhabited types. Look for the diagnostic emission point and modify it to produce a more helpful message tailored to accessors.
Tech stack
swift
Domain
compilers
Issue type
Feature
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.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
GitSwift
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
80