.NET 7 Method Group branch coverage issue

[g0dm0d3]

Hi guys!
After updating to .NET 7 new coverage issue was found.
It can be reproduced easily, you just need to reuse the same method group delegate.

Code:

namespace ClassLibrary1;

public class Class1
{
    public int[] Query1()
    {
        return new[] { 1, 2, 3 }.Select(Map).ToArray();
    }

    public int[] Query2()
    {
        return new[] { 1, 2, 3 }.Select(Map).ToArray();
    }

    private static int Map(int row) => row + 1;
}

Test:

using ClassLibrary1;
using NUnit.Framework;

namespace TestProject1;

public class Tests
{
    [Test]
    public void Test1()
    {
        new Class1().Query1();
        Assert.Pass();
    }

    [Test]
    public void Test2()
    {
        new Class1().Query2();
        Assert.Pass();
    }
}

Expected:
Full branch coverage (no branches at all)

Actual:
Partially covered (1 visits, 1 of 2 branches are covered)

Output:

Report:

<?xml version="1.0" encoding="utf-8"?>
<coverage line-rate="1" branch-rate="0.75" version="1.9" timestamp="1676057701" lines-covered="7" lines-valid="7" branches-covered="3" branches-valid="4">
  <sources>
    <source>F:\</source>
  </sources>
  <packages>
    <package name="ClassLibrary1" line-rate="1" branch-rate="0.75" complexity="5">
      <classes>
        <class name="ClassLibrary1.Class1" filename="ClassLibrary1\Class1.cs" line-rate="1" branch-rate="0.75" complexity="5">
          <methods>
            <method name="Query1" signature="()" line-rate="1" branch-rate="1" complexity="2">
              <lines>
                <line number="6" hits="1" branch="False" />
                <line number="7" hits="1" branch="True" condition-coverage="100% (2/2)">
                  <conditions>
                    <condition number="24" type="jump" coverage="100%" />
                  </conditions>
                </line>
                <line number="8" hits="1" branch="False" />
              </lines>
            </method>
            <method name="Query2" signature="()" line-rate="1" branch-rate="0.5" complexity="2">
              <lines>
                <line number="11" hits="1" branch="False" />
                <line number="12" hits="1" branch="True" condition-coverage="50% (1/2)">
                  <conditions>
                    <condition number="24" type="jump" coverage="50%" />
                  </conditions>
                </line>
                <line number="13" hits="1" branch="False" />
              </lines>
            </method>
            <method name="Map" signature="(System.Int32)" line-rate="1" branch-rate="1" complexity="1">
              <lines>
                <line number="15" hits="6" branch="False" />
              </lines>
            </method>
          </methods>
          <lines>
            <line number="6" hits="1" branch="False" />
            <line number="7" hits="1" branch="True" condition-coverage="100% (2/2)">
              <conditions>
                <condition number="24" type="jump" coverage="100%" />
              </conditions>
            </line>
            <line number="8" hits="1" branch="False" />
            <line number="11" hits="1" branch="False" />
            <line number="12" hits="1" branch="True" condition-coverage="50% (1/2)">
              <conditions>
                <condition number="24" type="jump" coverage="50%" />
              </conditions>
            </line>
            <line number="13" hits="1" branch="False" />
            <line number="15" hits="6" branch="False" />
          </lines>
        </class>
      </classes>
    </package>
  </packages>
</coverage>

Reproduced in .NET 7, Coverlet 3.2.0

[daveMueller]

Thanks for reporting this and providing a repro 🙏.

[github-actions]

This issue is stale because it has been open for 3 months with no activity.

[daveMueller]

I can reproduce this and will start working on it.

[g0dm0d3]

Thanks for fixing this @daveMueller !