Fix incorrect coverage await using in generic method

Documentation/Changelog.md

@@ -6,6 +6,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## Unreleased
 
+### Fixed
+- Fix incorrect coverage await using in generic method [#1490](https://github.com/coverlet-coverage/coverlet/issues/1490)
+
 ## Release date 2024-03-13
 ### Packages
 coverlet.msbuild 6.0.2

src/coverlet.core/Symbols/CecilSymbolHelper.cs

@@ -45,6 +45,22 @@ private static bool IsCompilerGenerated(FieldDefinition fieldDefinition)
       return fieldDefinition.DeclaringType.CustomAttributes.Any(ca => ca.AttributeType.FullName == typeof(CompilerGeneratedAttribute).FullName);
     }
 
+    private static bool IsCompilerGeneratedField(Instruction instruction, out FieldDefinition field)
+    {
+      switch (instruction.Operand)
+      {
+        case FieldDefinition fieldDefinition when IsCompilerGenerated(fieldDefinition):
+          field = fieldDefinition;
+          return true;
+        case FieldReference fieldReference when IsCompilerGenerated(fieldReference.Resolve()):
+          field = fieldReference.Resolve();
+          return true;
+        default:
+          field = null;
+          return false;
+      }
+    }
+
     private static bool IsMoveNextInsideAsyncStateMachine(MethodDefinition methodDefinition)
     {
       if (methodDefinition.FullName.EndsWith("::MoveNext()") && IsCompilerGenerated(methodDefinition))
@@ -537,11 +553,9 @@ static bool CheckForAsyncEnumerator(List<Instruction> instructions, Instruction
             (instructions[currentIndex - 2].OpCode == OpCodes.Ldarg ||
              instructions[currentIndex - 2].OpCode == OpCodes.Ldarg_0) &&
             instructions[currentIndex - 1].OpCode == OpCodes.Ldfld &&
-            (
-                (instructions[currentIndex - 1].Operand is FieldDefinition field && IsCompilerGenerated(field) && field.FieldType.FullName.StartsWith("System.Collections.Generic.IAsyncEnumerator")) ||
-                (instructions[currentIndex - 1].Operand is FieldReference fieldRef && IsCompilerGenerated(fieldRef.Resolve()) && fieldRef.FieldType.FullName.StartsWith("System.Collections.Generic.IAsyncEnumerator"))
-            )
-        )
+            IsCompilerGeneratedField(instructions[currentIndex - 1], out FieldDefinition field) &&
+            field.FieldType.FullName.StartsWith("System.Collections.Generic.IAsyncEnumerator")
+           )
         {
           return true;
         }
@@ -582,10 +596,8 @@ static bool CheckIfExceptionThrown(List<Instruction> instructions, Instruction i
         for (int i = currentIndex - 1; i >= minFieldIndex; --i)
         {
           if (instructions[i].OpCode == OpCodes.Ldfld &&
-              (
-                  (instructions[i].Operand is FieldDefinition field && IsCompilerGenerated(field) && field.FieldType.FullName == "System.Object") ||
-                  (instructions[i].Operand is FieldReference fieldRef && IsCompilerGenerated(fieldRef.Resolve()) && fieldRef.FieldType.FullName == "System.Object")
-              ))
+              IsCompilerGeneratedField(instructions[i], out FieldDefinition field) &&
+              field.FieldType.FullName == "System.Object")
           {
             // We expect the call to GetResult() to be no more than four
             // instructions before the loading of the field's value.
@@ -708,16 +720,16 @@ static bool CheckForSkipDisposal(List<Instruction> instructions, Instruction ins
 
         bool isFollowedByDisposeAsync = false;
 
-        if (instructions[currentIndex - 1].OpCode == OpCodes.Ldfld &&
-            instructions[currentIndex - 1].Operand is FieldDefinition field &&
-            IsCompilerGenerated(field))
+        if (instructions[currentIndex - 1].OpCode == OpCodes.Ldfld)
         {
+          if(! IsCompilerGeneratedField(instructions[currentIndex - 1], out FieldDefinition field)) return false;
+
           int maxReloadFieldIndex = Math.Min(currentIndex + 2, instructions.Count - 2);
 
           for (int i = currentIndex + 1; i <= maxReloadFieldIndex; ++i)
           {
             if (instructions[i].OpCode == OpCodes.Ldfld &&
-                instructions[i].Operand is FieldDefinition reloadedField &&
+                IsCompilerGeneratedField(instructions[i], out FieldDefinition reloadedField) &&
                 field.Equals(reloadedField) &&
                 instructions[i + 1].OpCode == OpCodes.Callvirt &&
                 instructions[i + 1].Operand is MethodReference method &&
@@ -758,8 +770,8 @@ instructions[i].Operand is FieldDefinition reloadedField &&
             if ((instructions[i].OpCode == OpCodes.Leave ||
                  instructions[i].OpCode == OpCodes.Leave_S) &&
                 instructions[i - 1].OpCode == OpCodes.Stfld &&
-                instructions[i - 1].Operand is FieldDefinition storeField &&
-                IsCompilerGenerated(storeField))
+                IsCompilerGeneratedField(instructions[i - 1], out FieldDefinition _)
+                )
             {
               return true;
             }
@@ -811,9 +823,7 @@ static bool CheckForCleanup(List<Instruction> instructions, Instruction instruct
 
           for (int i = currentIndex - 2; i >= minLoadFieldIndex; --i)
           {
-            if (instructions[i].OpCode == OpCodes.Ldfld &&
-                instructions[i].Operand is FieldDefinition loadedField &&
-                IsCompilerGenerated(loadedField))
+            if (instructions[i].OpCode == OpCodes.Ldfld && IsCompilerGeneratedField(instructions[i], out FieldDefinition _))
             {
               int minRethrowIndex = Math.Max(0, i - 4);
 
@@ -918,10 +928,8 @@ static bool DisposeCheck(List<Instruction> instructions, Instruction instruction
 
         if (currentIndex >= 2 &&
             instructions[currentIndex - 1].OpCode == OpCodes.Ldfld &&
-            (
-                (instructions[currentIndex - 1].Operand is FieldDefinition field && IsCompilerGenerated(field) && field.FullName.EndsWith("__disposeMode")) ||
-                (instructions[currentIndex - 1].Operand is FieldReference fieldRef && IsCompilerGenerated(fieldRef.Resolve()) && fieldRef.FullName.EndsWith("__disposeMode"))
-            ) &&
+            IsCompilerGeneratedField(instructions[currentIndex - 1], out FieldDefinition field) &&
+            field.FullName.EndsWith("__disposeMode") &&
             (instructions[currentIndex - 2].OpCode == OpCodes.Ldarg ||
              instructions[currentIndex - 2].OpCode == OpCodes.Ldarg_0))
         {

test/coverlet.core.tests/Coverage/CoverageTests.AwaitUsing.cs

@@ -23,6 +23,7 @@ public void AwaitUsing()
                   {
                     await (ValueTask)instance.HasAwaitUsing();
                     await (Task)instance.Issue914_Repro();
+                    await (Task)instance.Issue1490_Repro<string>();
 
                   }, persistPrepareResultToFile: pathSerialize[0]);
           return 0;
@@ -39,8 +40,10 @@ public void AwaitUsing()
                             (28, 1), (29, 1), (30, 1),
                             // Issue914_Repro_Example2()
                             (34, 1), (35, 1), (36, 1), (37, 1),
+                            // Issue1490_Repro<T>()
+                            (40, 1), (41, 1), (42, 1), (43, 1),
                             // MyTransaction.DisposeAsync()
-                            (43, 2), (44, 2), (45, 2)
+                            (48, 3), (49, 3), (50, 3)
                             )
         .ExpectedTotalNumberOfBranches(BuildConfiguration.Debug, 0);
       }

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

@@ -36,6 +36,11 @@ async private Task Issue914_Repro_Example2()
             await transaction.DisposeAsync();
         }
 
+        async public Task<T> Issue1490_Repro<T>()
+        {
+            await using var transaction = new MyTransaction();
+            return default(T);
+        }
 
         private class MyTransaction : IAsyncDisposable
         {