Skip branches in generated MoveNext() for singleton iterators

test/coverlet.core.tests/Coverage/CoverageTest.Yield.cs

@@ -41,7 +41,7 @@ public void Yield_Single()
         }
 
         [Fact]
-        public void Yield_Multiple()
+        public void Yield_Two()
         {
             string path = Path.GetTempFileName();
             try
@@ -100,5 +100,65 @@ public void Yield_SingleWithSwitch()
                 File.Delete(path);
             }
         }
+
+        [Fact]
+        public void Yield_Three()
+        {
+            string path = Path.GetTempFileName();
+            try
+            {
+                FunctionExecutor.Run(async (string[] pathSerialize) =>
+                {
+                    CoveragePrepareResult coveragePrepareResult = await TestInstrumentationHelper.Run<Yield>(instance =>
+                    {
+                        foreach (var _ in instance.Three()) ;
+
+                        return Task.CompletedTask;
+                    }, persistPrepareResultToFile: pathSerialize[0]);
+                    return 0;
+                }, new string[] { path });
+
+                CoverageResult result = TestInstrumentationHelper.GetCoverageResult(path);
+
+                result.Document("Instrumentation.Yield.cs")
+                      .Method("System.Boolean Coverlet.Core.Samples.Tests.Yield/<Three>d__3::MoveNext()")
+                      .AssertLinesCovered((42, 1), (43, 1), (44, 1))
+                      .ExpectedTotalNumberOfBranches(0);
+            }
+            finally
+            {
+                File.Delete(path);
+            }
+        }
+
+        [Fact]
+        public void Yield_Enumerable()
+        {
+            string path = Path.GetTempFileName();
+            try
+            {
+                FunctionExecutor.Run(async (string[] pathSerialize) =>
+                {
+                    CoveragePrepareResult coveragePrepareResult = await TestInstrumentationHelper.Run<Yield>(instance =>
+                    {
+                        foreach (var _ in instance.Enumerable(new[] { "one", "two", "three", "four" })) ;
+
+                        return Task.CompletedTask;
+                    }, persistPrepareResultToFile: pathSerialize[0]);
+                    return 0;
+                }, new string[] { path });
+
+                CoverageResult result = TestInstrumentationHelper.GetCoverageResult(path);
+
+                result.Document("Instrumentation.Yield.cs")
+                      .Method("System.Boolean Coverlet.Core.Samples.Tests.Yield/<Enumerable>d__4::MoveNext()")
+                      .AssertLinesCovered((51, 4))
+                      .ExpectedTotalNumberOfBranches(1);
+            }
+            finally
+            {
+                File.Delete(path);
+            }
+        }
     }
 }

test/coverlet.core.tests/Samples/Instrumentation.Yield.cs

@@ -36,5 +36,20 @@ public System.Collections.Generic.IEnumerable<int> OneWithSwitch(int n)
 
             yield return result;
         }
+
+        public System.Collections.Generic.IEnumerable<int> Three()
+        {
+            yield return 1;
+            yield return 2;
+            yield return 3;
+        }
+
+        public System.Collections.Generic.IEnumerable<string> Enumerable(System.Collections.Generic.IList<string> ls)
+        {
+            foreach (var item in ls)
+            {
+                yield return item;
+            }
+        }
     }
 }