dotnet/roslyn

Incorrect IDE0059 in a local function : Unnecessary assignment of a value

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#58,407 opened on Dec 18, 2021

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Area-IDEBugFeature - IDE0059help wanted

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Description

Version Used: dotnet 6.0.100 can also repro on master 9f8250964a72d53efe2d04fc0b2b07a48f04a45c via SharpLab (main Roslyn branch)

Steps to Reproduce:

public class C {
    public int M() {
        int i = 0;
        int Recurse()
        {
            if(i > 10) return i;
            i += 1;
            var a = Recurse();
            i += 1;
            var b = Recurse();
            i += 1;  // <<<<<<<<<<< IDE0059 ON THIS LINE
            return a + b;
        }
        return Recurse();
    }
}

Expected Behavior: No IDE0059 Actual Behavior: IDE0059 suggesting the line should be removed. Calling the function before removing the line returns 253 Calling the function after removing the line returns 198

Contributor guide

Research direction
Focus on the flow analysis of local functions in the IDE0059 rule. Trace how the assignment to 'i' is considered unnecessary when it actually affects the return value.
Tech stack
csharp
Domain
toolingbackend
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.
Stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
GitdotnetC#
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
50