dotnet/roslyn

IDE0059 - Unneccessary assignment is not reported if lambda is used in method

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#38,376 opened on Aug 29, 2019

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Area-IDEConcept-Continuous ImprovementFeature - IDE0059IDE-CodeStylehelp wanted

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Description

Version Used: VS16.3 Preview 2

Steps to Reproduce:

using System;

namespace TestNamespace
{
    public class TestClass
    {
        public void TestMethod()
        {
            var r = new Random();
            DoSmth(() => true);
        }

        private void DoSmth(Func<bool> func) => func();
    }
}

Expected Behavior: IDE0059 should be triggered for r.

Actual Behavior: IDE0059 is not triggered. If you comment out DoSmth(() => true);, IDE0059 is triggered as expected.

Contributor guide

Research direction
Examine the IDE0059 analyzer to understand why it does not report the unnecessary assignment when a lambda expression is present in the method. Consider if the lambda introduces a closure that affects the analysis, even though the variable is not captured. Check the logic for detecting unused local variables in the presence of lambda expressions.
Tech stack
csharp
Domain
compilers
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#Roslyn analyzers
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
65