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

@@ -137,7 +137,7 @@ public override IEnumerable<ILocationInfo> Locations {
                 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();
             }
         }
 
@@ -268,85 +268,78 @@ 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) {
+        if (strength > 0) {
+            return Name.GetHashCode();
         }
+        return GetHashCode();
+    }
 
-        internal override AnalysisValue UnionMergeTypes(AnalysisValue av, int strength) {
-            if (strength > 0 && av is ProtocolInfo pi && pi.Push()) {
-                try {
-                    var name = _protocols.OfType<NameProtocol>().FirstOrDefault();
-                    if (_protocols.Count == 1 && name != null) {
-                        return this;
-                    }
-
-                    var protocols = _protocols.Union(pi._protocols, out bool changed);
-                    if (!changed) {
-                        return this;
-                    }
+    internal override AnalysisValue UnionMergeTypes(AnalysisValue av, int strength) {
+        if (strength > 0 && av is ProtocolInfo pi && pi.Push()) {
+            try {
+                var name = _protocols.OfType<NameProtocol>().FirstOrDefault();
+                if (_protocols.Count == 1 && name != null) {
+                    return this;
+                }
 
-                    if (name != null) {
-                        protocols.Split<NameProtocol>(out _, out protocols);
-                        protocols = protocols.Add(name);
-                    }
+                var protocols = _protocols.Union(pi._protocols, out bool changed);
+                if (!changed) {
+                    return this;
+                }
 
-                    return new ProtocolInfo(DeclaringModule, State) {
-                        _protocols = protocols
-                    };
-                } finally {
-                    pi.Pop();
+                if (name != null) {
+                    protocols.Split<NameProtocol>(out _, out protocols);
+                    protocols = protocols.Add(name);
                 }
-            }
 
-            return this;
+                return new ProtocolInfo(DeclaringModule, State) {
+                    _protocols = protocols
+                };
+            } finally {
+                pi.Pop();
+            }
         }
 
-        public virtual IEnumerable<KeyValuePair<string, string>> GetRichDescription() {
-            var names = _protocols.OfType<NameProtocol>().ToArray();
-            Debug.Assert(names.Length <= 1, "Multiple names are not supported");
-            var name = names.FirstOrDefault();
-            if (name != null) {
-                return name.GetRichDescription();
-            }
+        return this;
+    }
 
-            var res = new List<KeyValuePair<string, string>>();
-            var namespaces = _protocols.OfType<NamespaceProtocol>().ToArray();
-            var tuples = _protocols.OfType<TupleProtocol>().ToArray();
-            var other = _protocols.OfType<Protocol>().Except(names).Except(namespaces).ToArray();
-
-            if (namespaces.Any()) {
-                var addComma = false;
-                res.Add(new KeyValuePair<string, string>(WellKnownRichDescriptionKinds.Misc, "("));
-                foreach (var p in namespaces) {
-                    if (addComma) {
-                        res.Add(new KeyValuePair<string, string>(WellKnownRichDescriptionKinds.Comma, ", "));
-                    }
-                    addComma = true;
-                    res.AddRange(p.GetRichDescription());
+    public virtual IEnumerable<KeyValuePair<string, string>> GetRichDescription() {
+        var names = _protocols.OfType<NameProtocol>().ToArray();
+        Debug.Assert(names.Length <= 1, "Multiple names are not supported");
+        var name = names.FirstOrDefault();
+        if (name != null) {
+            return name.GetRichDescription();
+        }
+
+        var res = new List<KeyValuePair<string, string>>();
+        var namespaces = _protocols.OfType<NamespaceProtocol>().ToArray();
+        var tuples = _protocols.OfType<TupleProtocol>().ToArray();
+        var other = _protocols.OfType<Protocol>().Except(names).Except(namespaces).ToArray();
+
+        if (namespaces.Any()) {
+            var addComma = false;
+            res.Add(new KeyValuePair<string, string>(WellKnownRichDescriptionKinds.Misc, "("));
+            foreach (var p in namespaces) {
+                if (addComma) {
+                    res.Add(new KeyValuePair<string, string>(WellKnownRichDescriptionKinds.Comma, ", "));
                 }
-                res.Add(new KeyValuePair<string, string>(WellKnownRichDescriptionKinds.Misc, ")"));
+                addComma = true;
+                res.AddRange(p.GetRichDescription());
             }
+            res.Add(new KeyValuePair<string, string>(WellKnownRichDescriptionKinds.Misc, ")"));
+        }
 
-            foreach (var p in other) {
-                res.AddRange(p.GetRichDescription().ToArray());
-            }
+        foreach (var p in other) {
+            res.AddRange(p.GetRichDescription().ToArray());
+        }
 
-            res.Add(new KeyValuePair<string, string>(WellKnownRichDescriptionKinds.EndOfDeclaration, string.Empty));
+        res.Add(new KeyValuePair<string, string>(WellKnownRichDescriptionKinds.EndOfDeclaration, string.Empty));
 
-            return res;
-        }
+        return res;
     }
 }
+}

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

@@ -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) {