when __new__ is called, and return type can't be determined, assume it creates an instance of the class, passed as the first parameter

Author: lostmsu

src/Analysis/Engine/Impl/Values/FunctionInfo.cs

@@ -19,6 +19,7 @@
 using System.Diagnostics;
 using System.Linq;
 using Microsoft.PythonTools.Analysis.Analyzer;
+using Microsoft.PythonTools.Analysis.AnalysisSetDetails;
 using Microsoft.PythonTools.Analysis.Infrastructure;
 using Microsoft.PythonTools.Interpreter;
 using Microsoft.PythonTools.Parsing;
@@ -146,6 +147,11 @@ public override IAnalysisSet Call(Node node, AnalysisUnit unit, IAnalysisSet[] a
                 CallSite = node
             };
 
+            // TODO: this should find cls parameter properly
+            if (res.Count == 0 && args.Length > 0 && Name == "__new__" && args[0] is ClassInfo cls) {
+                res = new AnalysisSetOneObject(cls.Instance);
+            }
+
             var r = res.Resolve(unit, context, out _);
             return r;
         }