Bug fixes

src/Analysis/Engine/Impl/Interpreter/Ast/AstPythonBoundMethod.cs

@@ -16,6 +16,7 @@
 
 using System.Collections.Generic;
 using Microsoft.PythonTools.Analysis;
+using Microsoft.PythonTools.Analysis.Infrastructure;
 
 namespace Microsoft.PythonTools.Interpreter.Ast {
     class AstPythonBoundMethod : IPythonBoundFunction, ILocatedMember {
@@ -27,6 +28,6 @@ public AstPythonBoundMethod(IPythonFunction function, IPythonType selfType) {
         public IPythonFunction Function { get; }
         public IPythonType SelfType { get; }
         public PythonMemberType MemberType => PythonMemberType.Method;
-        public IEnumerable<ILocationInfo> Locations => (Function as ILocatedMember)?.Locations;
+        public IEnumerable<ILocationInfo> Locations => (Function as ILocatedMember)?.Locations.MaybeEnumerate();
     }
 }

src/Analysis/Engine/Impl/Interpreter/Ast/AstPythonModule.cs

@@ -94,7 +94,7 @@ public string Documentation {
         public Uri DocumentUri { get; }
         public PythonMemberType MemberType => PythonMemberType.Module;
         public Dictionary<object, object> Properties { get; } = new Dictionary<object, object>();
-        public IEnumerable<ILocationInfo> Locations { get; }
+        public IEnumerable<ILocationInfo> Locations { get; } = Enumerable.Empty<ILocationInfo>();
 
         public int AnalysisVersion => 1;
         public IModuleContext AnalysisContext => null;

src/Analysis/Engine/Impl/Interpreter/Ast/AstPythonProperty.cs

@@ -14,7 +14,7 @@ public AstPythonProperty(
             ILocationInfo location
         ) {
             IsReadOnly = true;
-            Locations = new[] { location };
+            Locations = location != null ? new[] { location } : Enumerable.Empty<ILocationInfo>();
             FunctionDefinition = definition;
         }
 

src/Analysis/Engine/Impl/Interpreter/Ast/AstPythonType.cs

@@ -58,7 +58,7 @@ private AstPythonType(string name, Dictionary<string, IMember> members, IEnumera
             _members = members;
             _mro = Array.Empty<IPythonType>();
             DeclaringModule = NoDeclModule;
-            Locations = locations;
+            Locations = locations ?? Enumerable.Empty<ILocationInfo>();
         }
 
         internal void AddMembers(IEnumerable<KeyValuePair<string, IMember>> members, bool overwrite) {

src/Analysis/Engine/Impl/Interpreter/Ast/AstScrapedPythonModule.cs

@@ -90,7 +90,7 @@ public virtual IEnumerable<string> GetMemberNames(IModuleContext moduleContext)
         internal PythonAst Ast { get; private set; }
 
 #if DEBUG
-        public IEnumerable<ILocationInfo> Locations { get; private set; } = new LocationInfo[0];
+        public IEnumerable<ILocationInfo> Locations { get; private set; } = Enumerable.Empty<ILocationInfo>();
 #endif
 
         protected virtual List<string> GetScrapeArguments(IPythonInterpreterFactory factory) {

src/Analysis/Engine/Impl/MemberResult.cs

@@ -85,7 +85,7 @@ internal MemberResult(string name, Func<IEnumerable<AnalysisValue>> vars, Func<P
         /// 
         /// New in 1.5.
         /// </summary>
-        public IEnumerable<ILocationInfo> Locations => Values.SelectMany(ns => ns.Locations);
+        public IEnumerable<ILocationInfo> Locations => Values.SelectMany(ns => ns.Locations.MaybeEnumerate());
 
         public IEnumerable<AnalysisValue> Values => _vars.Value;
 

src/Analysis/Engine/Impl/ModuleTable.cs

@@ -416,7 +416,7 @@ internal override bool ModuleContainsMember(IModuleContext context, string name)
                                     return false;
                                 }
 
-                                foreach (var location in type.Locations) {
+                                foreach (var location in type.Locations.WhereNotNull()) {
                                     if (location.FilePath != modInfo.ProjectEntry.FilePath) {
                                         // declared in another module
                                         return false;

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

@@ -9,14 +9,14 @@
 // THIS CODE IS PROVIDED ON AN  *AS IS* BASIS, WITHOUT WARRANTIES OR CONDITIONS
 // OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION ANY
 // IMPLIED WARRANTIES OR CONDITIONS OF TITLE, FITNESS FOR A PARTICULAR PURPOSE,
-// MERCHANTABLITY OR NON-INFRINGEMENT.
+// MERCHANTABILITY OR NON-INFRINGEMENT.
 //
 // See the Apache Version 2.0 License for specific language governing
 // permissions and limitations under the License.
 
 using System.Collections.Generic;
 using System.Linq;
-using System.Text;
+using Microsoft.PythonTools.Analysis.Infrastructure;
 using Microsoft.PythonTools.Interpreter;
 using Microsoft.PythonTools.Parsing.Ast;
 
@@ -45,7 +45,7 @@ public override IAnalysisSet Call(Node node, AnalysisUnit unit, IAnalysisSet[] a
 
         public override IPythonProjectEntry DeclaringModule => Function.DeclaringModule;
         public override int DeclaringVersion => Function.DeclaringVersion;
-        public override IEnumerable<ILocationInfo> Locations => Function.Locations;
+        public override IEnumerable<ILocationInfo> Locations => Function.Locations.MaybeEnumerate();
         public override BuiltinTypeId TypeId => BuiltinTypeId.Function; 
 
         public IEnumerable<KeyValuePair<string, string>> GetRichDescription() {

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

@@ -111,15 +111,7 @@ public MemberContainerType ContainedValue {
 
         public virtual ILocatedMember GetLocatedMember() => null;
 
-        public override IEnumerable<ILocationInfo> Locations {
-            get {
-                var locatedMem = GetLocatedMember();
-                if (locatedMem != null) {
-                    return locatedMem.Locations;
-                }
-                return LocationInfo.Empty;
-            }
-        }
+        public override IEnumerable<ILocationInfo> Locations => GetLocatedMember()?.Locations.MaybeEnumerate();
 
         public override bool Equals(object obj) {
             if (obj is BuiltinNamespace<MemberContainerType> bn && GetType() == bn.GetType()) {

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

@@ -17,6 +17,7 @@
 using System.Collections.Generic;
 using System.Linq;
 using Microsoft.PythonTools.Analysis.Analyzer;
+using Microsoft.PythonTools.Analysis.Infrastructure;
 using Microsoft.PythonTools.Interpreter;
 using Microsoft.PythonTools.Parsing.Ast;
 
@@ -62,7 +63,7 @@ public IEnumerable<IReferenceable> GetDefinitions(string name, IMemberContainer
 
             var member = innerContainer.GetMember(context, name) as ILocatedMember;
             if (member != null) {
-                res.AddRange(member.Locations.Select(loc => new DefinitionList(loc)));
+                res.AddRange(member.Locations.MaybeEnumerate().Select(loc => new DefinitionList(loc)));
             }
 
             return res;

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

@@ -228,7 +228,7 @@ public override string ShortDescription {
             }
         }
 
-        public override IEnumerable<ILocationInfo> Locations => _members.SelectMany(m => m.Locations);
+        public override IEnumerable<ILocationInfo> Locations => _members.SelectMany(m => m.Locations.MaybeEnumerate());
 
         IModule IModule.GetChildPackage(IModuleContext context, string name) {
             var children = new List<AnalysisValue>();

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

@@ -129,17 +129,15 @@ public override PythonMemberType MemberType {
         }
 
 
-        internal override void AddReference(Node node, AnalysisUnit analysisUnit) {
-            _references.GetReferences(analysisUnit.ProjectEntry as ProjectEntry)?.AddReference(new EncodedLocation(analysisUnit, node));
-        }
+        internal override void AddReference(Node node, AnalysisUnit analysisUnit)
+            => _references.GetReferences(analysisUnit.ProjectEntry as ProjectEntry)?.AddReference(new EncodedLocation(analysisUnit, node));
 
         public override IEnumerable<ILocationInfo> Locations {
             get {
-                ReferenceList defns;
-                if (!_references.TryGetValue(DeclaringModule, out defns)) {
+                if (!_references.TryGetValue(DeclaringModule, out var defns)) {
                     return Enumerable.Empty<ILocationInfo>();
                 }
-                return defns.Definitions.Select(l => l.GetLocationInfo()).Where(l => l != null);
+                return defns.Definitions.Select(l => l.GetLocationInfo()).ExcludeDefault();
             }
         }
 
@@ -151,17 +149,14 @@ public override void AugmentAssign(AugmentedAssignStatement node, AnalysisUnit u
             }
         }
 
-        public override IAnalysisSet Await(Node node, AnalysisUnit unit) {
-            return AnalysisSet.UnionAll(_protocols.Select(p => p.Await(node, unit)));
-        }
+        public override IAnalysisSet Await(Node node, AnalysisUnit unit)
+            => AnalysisSet.UnionAll(_protocols.Select(p => p.Await(node, unit)));
 
-        public override IAnalysisSet BinaryOperation(Node node, AnalysisUnit unit, PythonOperator operation, IAnalysisSet rhs) {
-            return AnalysisSet.UnionAll(_protocols.Select(p => p.BinaryOperation(node, unit, operation, rhs)));
-        }
+        public override IAnalysisSet BinaryOperation(Node node, AnalysisUnit unit, PythonOperator operation, IAnalysisSet rhs)
+            => AnalysisSet.UnionAll(_protocols.Select(p => p.BinaryOperation(node, unit, operation, rhs)));
 
-        public override IAnalysisSet Call(Node node, AnalysisUnit unit, IAnalysisSet[] args, NameExpression[] keywordArgNames) {
-            return AnalysisSet.UnionAll(_protocols.Select(p => p.Call(node, unit, args, keywordArgNames)));
-        }
+        public override IAnalysisSet Call(Node node, AnalysisUnit unit, IAnalysisSet[] args, NameExpression[] keywordArgNames)
+            => AnalysisSet.UnionAll(_protocols.Select(p => p.Call(node, unit, args, keywordArgNames)));
 
         public override void DeleteMember(Node node, AnalysisUnit unit, string name) {
             foreach (var p in _protocols) {
@@ -273,22 +268,10 @@ public override bool Equals(object obj) {
 
         public override int GetHashCode() => ObjectComparer.Instance.GetHashCode(_protocols);
 
-        internal override bool UnionEquals(AnalysisValue av, int strength) {
-            if (av is ProtocolInfo pi) {
-                if (strength > 0) {
-                    return Name == pi.Name;
-                }
-                return ObjectComparer.Instance.Equals(_protocols, pi._protocols);
-            }
-            return false;
-        }
+        internal override bool UnionEquals(AnalysisValue av, int strength)
+            => av is ProtocolInfo pi ? ObjectComparer.Instance.Equals(_protocols, pi._protocols) : false;
 
-        internal override int UnionHashCode(int strength) {
-            if (strength > 0) {
-                return Name.GetHashCode();
-            }
-            return GetHashCode();
-        }
+        internal override int UnionHashCode(int strength) => strength > 0 ? Name.GetHashCode() : GetHashCode();
 
         internal override AnalysisValue UnionMergeTypes(AnalysisValue av, int strength) {
             if (strength > 0 && av is ProtocolInfo pi && pi.Push()) {

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

@@ -63,20 +63,19 @@ protected IAnalysisSet MakeMethod(string qualname, IReadOnlyList<IAnalysisSet> a
 
         public override PythonMemberType MemberType => PythonMemberType.Unknown;
 
-        // Do not return any default values from protocols. We call these directly and handle null.
-        public override IAnalysisSet Await(Node node, AnalysisUnit unit) => null;
-        public override IAnalysisSet BinaryOperation(Node node, AnalysisUnit unit, PythonOperator operation, IAnalysisSet rhs) => null;
-        public override IAnalysisSet GetAsyncEnumeratorTypes(Node node, AnalysisUnit unit) => null;
-        public override IAnalysisSet GetAsyncIterator(Node node, AnalysisUnit unit) => null;
-        public override IAnalysisSet GetDescriptor(Node node, AnalysisValue instance, AnalysisValue context, AnalysisUnit unit) => null;
-        public override IAnalysisSet GetDescriptor(PythonAnalyzer projectState, AnalysisValue instance, AnalysisValue context) => null;
-        public override IAnalysisSet GetEnumeratorTypes(Node node, AnalysisUnit unit) => null;
-        public override IAnalysisSet GetIndex(Node node, AnalysisUnit unit, IAnalysisSet index) => null;
-        public override IAnalysisSet GetInstanceType() => null;
-        public override IEnumerable<KeyValuePair<IAnalysisSet, IAnalysisSet>> GetItems() => null;
-        public override IAnalysisSet GetIterator(Node node, AnalysisUnit unit) => null;
-        public override IAnalysisSet GetReturnForYieldFrom(Node node, AnalysisUnit unit) => null;
-        public override IAnalysisSet UnaryOperation(Node node, AnalysisUnit unit, PythonOperator operation) => null;
+        public override IAnalysisSet Await(Node node, AnalysisUnit unit) => AnalysisSet.Empty;
+        public override IAnalysisSet BinaryOperation(Node node, AnalysisUnit unit, PythonOperator operation, IAnalysisSet rhs) => AnalysisSet.Empty;
+        public override IAnalysisSet GetAsyncEnumeratorTypes(Node node, AnalysisUnit unit) => AnalysisSet.Empty;
+        public override IAnalysisSet GetAsyncIterator(Node node, AnalysisUnit unit) => AnalysisSet.Empty;
+        public override IAnalysisSet GetDescriptor(Node node, AnalysisValue instance, AnalysisValue context, AnalysisUnit unit) => AnalysisSet.Empty;
+        public override IAnalysisSet GetDescriptor(PythonAnalyzer projectState, AnalysisValue instance, AnalysisValue context) => AnalysisSet.Empty;
+        public override IAnalysisSet GetEnumeratorTypes(Node node, AnalysisUnit unit) => AnalysisSet.Empty;
+        public override IAnalysisSet GetIndex(Node node, AnalysisUnit unit, IAnalysisSet index) => AnalysisSet.Empty;
+        public override IAnalysisSet GetInstanceType() => AnalysisSet.Empty;
+        public override IEnumerable<KeyValuePair<IAnalysisSet, IAnalysisSet>> GetItems() => Enumerable.Empty< KeyValuePair<IAnalysisSet, IAnalysisSet>>();
+        public override IAnalysisSet GetIterator(Node node, AnalysisUnit unit) => AnalysisSet.Empty;
+        public override IAnalysisSet GetReturnForYieldFrom(Node node, AnalysisUnit unit) => AnalysisSet.Empty;
+        public override IAnalysisSet UnaryOperation(Node node, AnalysisUnit unit, PythonOperator operation) => AnalysisSet.Empty;
 
         public override IDictionary<string, IAnalysisSet> GetAllMembers(IModuleContext moduleContext, GetMemberOptions options = GetMemberOptions.None) {
             EnsureMembers();
@@ -131,21 +130,22 @@ class NameProtocol : Protocol {
         private readonly BuiltinTypeId _typeId;
         private List<KeyValuePair<string, string>> _richDescription;
 
-        public NameProtocol(ProtocolInfo self, string name, string documentation = null, BuiltinTypeId typeId = BuiltinTypeId.Unknown, PythonMemberType memberType = PythonMemberType.Unknown) : base(self) {
+        public NameProtocol(
+            ProtocolInfo self, 
+            string name, 
+            string documentation = null, 
+            BuiltinTypeId typeId = BuiltinTypeId.Unknown, 
+            PythonMemberType memberType = PythonMemberType.Unknown) 
+            : base(self) {
             _name = name;
             _doc = documentation;
             _typeId = typeId;
             MemberType = memberType;
             _richDescription = new List<KeyValuePair<string, string>> { new KeyValuePair<string, string>(WellKnownRichDescriptionKinds.Type, _name) };
         }
 
-        public NameProtocol(ProtocolInfo self, IPythonType type) : base(self) {
-            _name = type.Name;
-            _doc = type.Documentation;
-            _typeId = type.TypeId;
-            MemberType = type.MemberType;
-            _richDescription = new List<KeyValuePair<string, string>> { new KeyValuePair<string, string>(WellKnownRichDescriptionKinds.Type, _name) };
-        }
+        public NameProtocol(ProtocolInfo self, IPythonType type) 
+            : this(self, type.Name, type.Documentation, type.TypeId, type.MemberType) { }
 
         public void ExtendDescription(KeyValuePair<string, string> part) {
             _richDescription.Add(part);
@@ -851,12 +851,12 @@ public override IAnalysisSet GetDescriptor(PythonAnalyzer projectState, Analysis
         public override IEnumerable<KeyValuePair<IAnalysisSet, IAnalysisSet>> GetItems() => _actualType.GetItems();
         public override IAnalysisSet GetIterator(Node node, AnalysisUnit unit) => _actualType.GetIterator(node, unit);
         public override IAnalysisSet GetReturnForYieldFrom(Node node, AnalysisUnit unit) => _actualType.GetReturnForYieldFrom(node, unit);
-        public override IEnumerable<ILocationInfo> Locations => _actualType.Locations;
+        public override IEnumerable<ILocationInfo> Locations => _actualType.Locations.MaybeEnumerate();
         public override IMro Mro => _actualType.Mro;
-        public override IEnumerable<OverloadResult> Overloads => _actualType.Overloads;
+        public override IEnumerable<OverloadResult> Overloads => _actualType.Overloads.MaybeEnumerate();
         public override int? GetLength() => _actualType.GetLength();
         internal override IAnalysisSet Resolve(AnalysisUnit unit, ResolutionContext context) => _actualType.Resolve(unit, context);
-        internal override IEnumerable<ILocationInfo> References => _actualType.References;
+        internal override IEnumerable<ILocationInfo> References => _actualType.References.MaybeEnumerate();
         public override IAnalysisSet ReverseBinaryOperation(Node node, AnalysisUnit unit, PythonOperator operation, IAnalysisSet rhs)
             => _actualType.ReverseBinaryOperation(node, unit, operation, rhs);
 

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

@@ -9,14 +9,15 @@
 // THIS CODE IS PROVIDED ON AN  *AS IS* BASIS, WITHOUT WARRANTIES OR CONDITIONS
 // OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION ANY
 // IMPLIED WARRANTIES OR CONDITIONS OF TITLE, FITNESS FOR A PARTICULAR PURPOSE,
-// MERCHANTABLITY OR NON-INFRINGEMENT.
+// MERCHANTABILITY OR NON-INFRINGEMENT.
 //
 // See the Apache Version 2.0 License for specific language governing
 // permissions and limitations under the License.
 
 using System;
 using System.Collections.Generic;
 using System.Linq;
+using Microsoft.PythonTools.Analysis.Infrastructure;
 using Microsoft.PythonTools.Interpreter;
 using Microsoft.PythonTools.Parsing.Ast;
 
@@ -208,52 +209,17 @@ public override bool IsOfType(IAnalysisSet klass) {
             return _original.IsOfType(klass);
         }
 
-        public override IEnumerable<ILocationInfo> Locations {
-            get {
-                if (_original == null) {
-                    return new LocationInfo[0];
-                }
-                return _original.Locations;
-            }
-        }
+        public override IEnumerable<ILocationInfo> Locations => _original.Locations?.MaybeEnumerate();
 
-        public override string Name => _original == null ? base.Name : this._original.Name;
+        public override string Name => _original == null ? base.Name : _original.Name;
 
-        public override IEnumerable<OverloadResult> Overloads {
-            get {
-                if (_original == null) {
-                    return new OverloadResult[0];
-                }
-                return _original.Overloads;
-            }
-        }
+        public override IEnumerable<OverloadResult> Overloads =>_original.Overloads.MaybeEnumerate();
 
-        public override IPythonType PythonType {
-            get {
-                if (_original == null) {
-                    return null;
-                }
-                return _original.PythonType;
-            }
-        }
+        public override IPythonType PythonType => _original?.PythonType;
 
-        internal override IEnumerable<ILocationInfo> References {
-            get {
-                if (_original == null) {
-                    return new LocationInfo[0];
-                }
-                return _original.References;
-            }
-        }
+        internal override IEnumerable<ILocationInfo> References => _original.References?.MaybeEnumerate();
 
-        public override PythonMemberType MemberType {
-            get {
-                if (_original == null) {
-                    return PythonMemberType.Unknown;
-                }
-                return _original.MemberType;
-            }
-        }
+        public override PythonMemberType MemberType => _original == null ? PythonMemberType.Unknown : _original.MemberType;
 
         public override IAnalysisSet ReverseBinaryOperation(Node node, AnalysisUnit unit, Parsing.PythonOperator operation, IAnalysisSet rhs) {
             if (_original == null) {