fix (#164)

Co-authored-by: Xin Shi <xinshi@microsoft.com>

Cilsil/Cil/Parsers/InstructionParser.cs

@@ -703,6 +703,7 @@ namespace Cilsil.Cil.Parsers
                                                out Call methodCall,
                                                bool isConstructorCall = false)
         {
+            ProcedureName procName;
             callArgs = new List<Call.CallArg>();
             returnType = calledMethod.ReturnType;
             var paramCount = calledMethod.Parameters.Count;
@@ -715,10 +716,33 @@ namespace Cilsil.Cil.Parsers
                 callArgs.Add(new Call.CallArg(thisExpr, thisType));
                 paramCount--;
             }
-            var funcExp = new ConstExpression(new ProcedureName(calledMethod));
             callArgs.AddRange(state.PopMany(paramCount)
                                    .Select(p => new Call.CallArg(p.Item1, p.Item2))
                                    .ToList());
+            var x = calledMethod.GetCompatibleFullName();
+            // When objects are handled using C#'s using construct, the compiler invokes the
+            // System.IDisposable method for dispose. This is problematic when applied to
+            // user-defined types with custom dispose, as then we will not apply the spec computed
+            // for the user-defined dispose.
+            if (calledMethod.GetCompatibleFullName().Contains("System.IDisposable::Dispose") &&
+                callArgs.First().Type is Tptr objectPtr &&
+                objectPtr.Type is Tstruct disposeType)
+            {
+                procName = new ProcedureName(
+                    calledMethod.Name,
+                    calledMethod.Parameters.Select(
+                        p => p.ParameterType.GetCompatibleFullName()).ToList(),
+                    disposeType.StructName,
+                    calledMethod.ReturnType.GetCompatibleFullName(),
+                    !calledMethod.HasThis);
+                isVirtual = false;
+            }
+            else
+            {
+                procName = new ProcedureName(calledMethod);
+            }
+            var funcExp = new ConstExpression(procName);
+
             var callFlags = new Call.CallFlags(isVirtual, false, false);
             returnVariable = state.GetIdentifier(Identifier.IdentKind.Normal);
             methodCall = new Call(returnId: returnVariable,