Merge pull request #6 from apiiro/ohad/fix-generics-stack-overflow

Fixed stack overflow with generics.

Author: ariel-levy

src/Analysis/Ast/Impl/Specializations/Typing/Types/GenericType.cs

@@ -128,11 +128,15 @@ public IMember CreateInstance(IArgumentSet args) {
                 throw new ArgumentException(@"Generic type instance construction arguments must be all of IPythonType", nameof(args));
             }
             var specific = CreateSpecificType(args);
-            return specific == null
+            return specific == null || IsSameType(specific)
                 ? DeclaringModule.Interpreter.UnknownType.CreateInstance(args)
                 : specific.CreateInstance(args);
         }
 
+        private bool IsSameType(IPythonType specific)
+            => specific.MemberType == PythonMemberType.Generic &&
+               this.Name == specific.Name;
+
         public IMember Call(IPythonInstance instance, string memberName, IArgumentSet args) => DeclaringModule.Interpreter.UnknownType;
         public IMember Index(IPythonInstance instance, IArgumentSet args) => DeclaringModule.Interpreter.UnknownType;
 

src/Analysis/Ast/Test/GenericsTests.cs

@@ -13,6 +13,7 @@
 // See the Apache Version 2.0 License for specific language governing
 // permissions and limitations under the License.
 
+using System;
 using System.Linq;
 using System.Threading.Tasks;
 using FluentAssertions;
@@ -1412,6 +1413,23 @@ import pathlib
             analysis.Should().HaveVariable("root").OfType("Path");
             analysis.Should().HaveVariable("subdir").OfType("PurePath");
             analysis.Should().HaveVariable("child").OfType("PurePath");
+        }        
+
+        [TestMethod, Priority(0)]
+        public async Task GenericStackOverflowBub() {
+            /*
+             * Apiiro fix.
+             * The code below created stack overflow if SpecializedGenericType.CreateInstance
+             * Just checking we are not crushing here. 
+             */
+            const string code = @"
+from typing import Union, Sequence, TypeVar
+_T = TypeVar(""_T"")
+_NestedSequence = Sequence[Sequence[_T]]
+_ArrayLike = _NestedSequence[_T]
+";
+            await GetAnalysisAsync(code, PythonVersions.Python37);
+            Assert.IsTrue(true);
         }
     }
 }