dotnet/roslyn

IDE0059 and code fix for use discard but instead (correctly) simplifies to type match

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#57,748 opened on Nov 13, 2021

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Area-IDEBugFeature - IDE0059help wanted

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Description

Version Used: .NET 6.0.100

Steps to Reproduce:

  1. Have a type match like that Foo foo => throw new NotImplementedException(),
  2. Code Analyzers correctly detect IDE0059 unnecessary assignment
  3. Code Fixes suggest to use discard (not wrong but so C# 8?)
  4. Code Fixes executes and emits the following ... Foo => throw new NotImplementedException(),

Expected Behavior: Either, Code Fix does what it says in the UI (introduce a discard) OR is correctly named/described.

Actual Behavior: Code Fix does something else then what it actually says. Not that the refactoring itself is wrong ... i am happy with the overall outcome but the description meanwhile is misleading.

Contributor guide

Research direction
Trace the IDE0059 code fix provider in the Roslyn source code to understand why it removes the assignment instead of introducing a discard, and verify whether the fix description is misleading.
Tech stack
csharp
Domain
compilersdeveloper experience
Issue type
Bug
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
C#Git
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
70