dotnet/roslyn

"Redundant assignment" analysis does not consider recursive code path

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#47,655 opened on Sep 12, 2020

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Description

Version Used: VS 2019 16.7.3

Steps to Reproduce:

  1. Create new .NET Core console app.
  2. Paste the following code.
static void Foo(Exception ex)
{
    var indentLevel = 0;

    void Bar(Exception e)
    {
        indentLevel++;

        if (indentLevel < 5)
            Bar(e);

        indentLevel--;
    }

    Bar(ex);
}

Expected Behavior: No analysis complaints

Actual Behavior:

VS claims that indentLevel-- is a redundant assignment.

This is true for the top level call to Bar but not true for the recursive calls that reference the same indentLevel variable.

Contributor guide

Research direction
Investigate the data flow analysis for recursive local functions to understand why the assignment after recursion is considered redundant.
Tech stack
csharp
Domain
tooling
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.
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#
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
55