Further updates after today's meeting.

src/Compilers/Core/Portable/Compilation/Extensions.cs

@@ -12,6 +12,17 @@ namespace Microsoft.CodeAnalysis
 {
     public static class ModelExtensions
     {
+        /// <summary>
+        /// Gets a semantic model based on this semantic model that can return information about calculated
+        /// nullability. This model is used to query for information about expressions that can have
+        /// inferred nullability, such as references, inferred type parameters, declared nullability
+        /// of <c>var</c> variables or discard expression, or lambda parameters.
+        /// </summary>
+        public static SemanticModel GetNullabilityAwareSemanticModel(this SemanticModel semanticModel, CancellationToken cancellationToken = default)
+        {
+            throw new NotImplementedException();
+        }
+
         /// <summary>
         /// Gets symbol information about a syntax node.
         /// </summary>
@@ -24,12 +35,6 @@ public static class ModelExtensions
             return semanticModel.GetSymbolInfo(node, cancellationToken);
         }
 
-        // If there is no single symbol, return will be the same as GetSymbolInfoWithNullability
-        public static SymbolInfo GetSymbolInfoWithNullability(this SemanticModel semanticModel, SyntaxNode, CancellationToken ct = default)
-        {
-            throw new NotImplementedException();
-        }
-
         /// <summary>
         /// Binds the node in the context of the specified location and get semantic information
         /// such as type, symbols and diagnostics. This method is used to get semantic information
@@ -66,11 +71,6 @@ public static SymbolInfo GetSpeculativeSymbolInfo(this SemanticModel semanticMod
             return semanticModel.GetTypeInfo(node, cancellationToken);
         }
 
-        public static TypeInfo GetTypeInfoWithNullability(this SemanticModel semanticModel, SyntaxNode node, CancellationToken cancellationToken = default)
-        {
-            throw new NotImplementedException();
-        }
-
         /// <summary>
         /// If "nameSyntax" resolves to an alias name, return the IAliasSymbol corresponding
         /// to A. Otherwise return null.
@@ -146,46 +146,6 @@ public static TypeInfo GetSpeculativeTypeInfo(this SemanticModel semanticModel,
             return semanticModel.GetDeclaredSymbolForNode(declaration, cancellationToken);
         }
 
-        public static TypeInfo GetTypeWithNullability(this SemanticModel semanticModel, IDiscardSymbol discard, CancellationToken ct = default)
-        {
-            throw new NotImplementedException();
-        }
-
-        public static TypeInfo GetTypeWithNullability(this SemanticModel semanticModel, IEventSymbol eventSymbol, CancellationToken ct = default)
-        {
-            throw new NotImplementedException();
-        }
-
-        public static TypeInfo GetTypeWithNullability(this SemanticModel semanticModel, IFieldSymbol field, CancellationToken ct = default)
-        {
-            throw new NotImplementedException();
-        }
-
-        public static TypeInfo GetTypeWithNullability(this SemanticModel semanticModel, ILocalSymbol local, CancellationToken ct = default)
-        {
-            throw new NotImplementedException();
-        }
-
-        public static TypeInfo GetReturnTypeWithNullability(this SemanticModel semanticModel, IMethodSymbol method, CancellationToken ct = default)
-        {
-            throw new NotImplementedException();
-        }
-
-        public static ImmutableArray<TypeInfo> GetTypeParametersWithNullability(this SemanticModel semanticModel, IMethodSymbol method, CancellationToken ct = default)
-        {
-            throw new NotImplementedException();
-        }
-
-        public static TypeInfo GetReceiverTypeWithNullability(this SemanticModel semanticModel, IMethodSymbol method, CancellationToken ct = default)
-        {
-            throw new NotImplementedException();
-        }
-
-        public static TypeInfo GetTypeWithNullability(this SemanticModel semanticModel, IParameterSymbol local, CancellationToken ct = default)
-        {
-            throw new NotImplementedException();
-        }
-
         /// <summary>
         /// Gets a list of method or indexed property symbols for a syntax node.
         /// </summary>

src/Compilers/Core/Portable/PublicAPI.Unshipped.txt

@@ -16,14 +16,15 @@ Microsoft.CodeAnalysis.FlowAnalysis.IStaticLocalInitializationSemaphoreOperation
 Microsoft.CodeAnalysis.FlowAnalysis.IStaticLocalInitializationSemaphoreOperation.Local.get -> Microsoft.CodeAnalysis.ILocalSymbol
 Microsoft.CodeAnalysis.IArrayTypeSymbol.ElementNullability.get -> Microsoft.CodeAnalysis.Nullability
 Microsoft.CodeAnalysis.IDiscardSymbol.Nullability.get -> Microsoft.CodeAnalysis.Nullability
-Microsoft.CodeAnalysis.IEventSymbol.DeclaredNullability.get -> Microsoft.CodeAnalysis.Nullability
-Microsoft.CodeAnalysis.IFieldSymbol.DeclaredNullability.get -> Microsoft.CodeAnalysis.Nullability
-Microsoft.CodeAnalysis.ILocalSymbol.DeclaredNullability.get -> Microsoft.CodeAnalysis.Nullability
+Microsoft.CodeAnalysis.IEventSymbol.Nullability.get -> Microsoft.CodeAnalysis.Nullability
+Microsoft.CodeAnalysis.IFieldSymbol.Nullability.get -> Microsoft.CodeAnalysis.Nullability
+Microsoft.CodeAnalysis.ILocalSymbol.Nullability.get -> Microsoft.CodeAnalysis.Nullability
+Microsoft.CodeAnalysis.IMethodSymbol.ReceiverNullability.get -> Microsoft.CodeAnalysis.Nullability
 Microsoft.CodeAnalysis.IMethodSymbol.ReturnNullability.get -> Microsoft.CodeAnalysis.Nullability
-Microsoft.CodeAnalysis.IMethodSymbol.TypeArgumentsNullability.get -> System.Collections.Immutable.ImmutableArray<Microsoft.CodeAnalysis.Nullability>
+Microsoft.CodeAnalysis.IMethodSymbol.TypeArgumentsNullabilities.get -> System.Collections.Immutable.ImmutableArray<Microsoft.CodeAnalysis.Nullability>
 Microsoft.CodeAnalysis.INamedTypeSymbol.TypeArgumentsNullability.get -> System.Collections.Immutable.ImmutableArray<Microsoft.CodeAnalysis.Nullability>
 Microsoft.CodeAnalysis.IOperation.SemanticModel.get -> Microsoft.CodeAnalysis.SemanticModel
-Microsoft.CodeAnalysis.IParameterSymbol.DeclaredNullability.get -> Microsoft.CodeAnalysis.Nullability
+Microsoft.CodeAnalysis.IParameterSymbol.Nullability.get -> Microsoft.CodeAnalysis.Nullability
 Microsoft.CodeAnalysis.IPropertySymbol.DeclaredNullability.get -> Microsoft.CodeAnalysis.Nullability
 Microsoft.CodeAnalysis.ISymbol.ToDisplayParts(Microsoft.CodeAnalysis.Nullability nullability, Microsoft.CodeAnalysis.SymbolDisplayFormat format = null) -> System.Collections.Immutable.ImmutableArray<Microsoft.CodeAnalysis.SymbolDisplayPart>
 Microsoft.CodeAnalysis.ISymbol.ToDisplayString(Microsoft.CodeAnalysis.Nullability nullability, Microsoft.CodeAnalysis.SymbolDisplayFormat format = null) -> string
@@ -156,13 +157,7 @@ static Microsoft.CodeAnalysis.FlowAnalysis.ControlFlowGraph.Create(Microsoft.Cod
 static Microsoft.CodeAnalysis.FlowAnalysis.ControlFlowGraph.Create(Microsoft.CodeAnalysis.Operations.IParameterInitializerOperation initializer, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) -> Microsoft.CodeAnalysis.FlowAnalysis.ControlFlowGraph
 static Microsoft.CodeAnalysis.FlowAnalysis.ControlFlowGraph.Create(Microsoft.CodeAnalysis.Operations.IPropertyInitializerOperation initializer, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) -> Microsoft.CodeAnalysis.FlowAnalysis.ControlFlowGraph
 static Microsoft.CodeAnalysis.FlowAnalysis.ControlFlowGraph.Create(Microsoft.CodeAnalysis.SyntaxNode node, Microsoft.CodeAnalysis.SemanticModel semanticModel, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) -> Microsoft.CodeAnalysis.FlowAnalysis.ControlFlowGraph
-static Microsoft.CodeAnalysis.ModelExtensions.GetReturnTypeWithNullability(this Microsoft.CodeAnalysis.SemanticModel semanticModel, Microsoft.CodeAnalysis.IMethodSymbol method, System.Threading.CancellationToken ct = default(System.Threading.CancellationToken)) -> Microsoft.CodeAnalysis.TypeInfo
-static Microsoft.CodeAnalysis.ModelExtensions.GetSymbolInfoWithNullability(this Microsoft.CodeAnalysis.SemanticModel semanticModel, Microsoft.CodeAnalysis.SyntaxNode , System.Threading.CancellationToken ct = default(System.Threading.CancellationToken)) -> Microsoft.CodeAnalysis.SymbolInfo
-static Microsoft.CodeAnalysis.ModelExtensions.GetTypeInfoWithNullability(this Microsoft.CodeAnalysis.SemanticModel semanticModel, Microsoft.CodeAnalysis.SyntaxNode node, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) -> Microsoft.CodeAnalysis.TypeInfo
-static Microsoft.CodeAnalysis.ModelExtensions.GetTypeWithNullability(this Microsoft.CodeAnalysis.SemanticModel semanticModel, Microsoft.CodeAnalysis.IEventSymbol eventSymbol, System.Threading.CancellationToken ct = default(System.Threading.CancellationToken)) -> Microsoft.CodeAnalysis.TypeInfo
-static Microsoft.CodeAnalysis.ModelExtensions.GetTypeWithNullability(this Microsoft.CodeAnalysis.SemanticModel semanticModel, Microsoft.CodeAnalysis.IFieldSymbol field, System.Threading.CancellationToken ct = default(System.Threading.CancellationToken)) -> Microsoft.CodeAnalysis.TypeInfo
-static Microsoft.CodeAnalysis.ModelExtensions.GetTypeWithNullability(this Microsoft.CodeAnalysis.SemanticModel semanticModel, Microsoft.CodeAnalysis.ILocalSymbol local, System.Threading.CancellationToken ct = default(System.Threading.CancellationToken)) -> Microsoft.CodeAnalysis.TypeInfo
-static Microsoft.CodeAnalysis.ModelExtensions.GetTypeWithNullability(this Microsoft.CodeAnalysis.SemanticModel semanticModel, Microsoft.CodeAnalysis.IParameterSymbol local, System.Threading.CancellationToken ct = default(System.Threading.CancellationToken)) -> Microsoft.CodeAnalysis.TypeInfo
+static Microsoft.CodeAnalysis.ModelExtensions.GetNullabilityAwareSemanticModel(this Microsoft.CodeAnalysis.SemanticModel semanticModel, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) -> Microsoft.CodeAnalysis.SemanticModel
 virtual Microsoft.CodeAnalysis.Operations.OperationVisitor.VisitCaughtException(Microsoft.CodeAnalysis.FlowAnalysis.ICaughtExceptionOperation operation) -> void
 virtual Microsoft.CodeAnalysis.Operations.OperationVisitor.VisitFlowCapture(Microsoft.CodeAnalysis.FlowAnalysis.IFlowCaptureOperation operation) -> void
 virtual Microsoft.CodeAnalysis.Operations.OperationVisitor.VisitFlowCaptureReference(Microsoft.CodeAnalysis.FlowAnalysis.IFlowCaptureReferenceOperation operation) -> void

src/Compilers/Core/Portable/SymbolDisplay/SymbolDisplayPartKind.cs

@@ -66,9 +66,7 @@ public enum SymbolDisplayPartKind
         /// <summary>The name of a type parameter.</summary>
         TypeParameterName = 26,
         /// <summary>The name of a query range variable..</summary>
-        RangeVariableName = 27,
-        /// <summary>The nullability of the symbol.</summary>
-        Nullability = 28
+        RangeVariableName = 27
     }
 
     internal static class InternalSymbolDisplayPartKind

src/Compilers/Core/Portable/Symbols/IDiscardSymbol.cs

@@ -14,5 +14,10 @@ public interface IDiscardSymbol : ISymbol
         /// The type of the discarded value.
         /// </summary>
         ITypeSymbol Type { get; }
+
+        /// <summary>
+        /// The nullability of the discard symbol.
+        /// </summary>
+        Nullability Nullability { get; }
     }
 }

src/Compilers/Core/Portable/Symbols/IEventSymbol.cs

@@ -19,6 +19,11 @@ public interface IEventSymbol : ISymbol
         /// </summary>
         ITypeSymbol Type { get; }
 
+        /// <summary>
+        /// The nullability of the event
+        /// </summary>
+        Nullability Nullability { get; }
+
         /// <summary>
         /// Returns true if the event is a WinRT type event.
         /// </summary>

src/Compilers/Core/Portable/Symbols/IFieldSymbol.cs

@@ -44,6 +44,11 @@ public interface IFieldSymbol : ISymbol
         /// </summary>
         ITypeSymbol Type { get; }
 
+        /// <summary>
+        /// The declared nullability of this field
+        /// </summary>
+        Nullability Nullability { get; }
+
         /// <summary>
         /// Returns false if the field wasn't declared as "const", or constant value was omitted or erroneous.
         /// True otherwise.

src/Compilers/Core/Portable/Symbols/ILocalSymbol.cs

@@ -16,6 +16,11 @@ public interface ILocalSymbol : ISymbol
         /// </summary>
         ITypeSymbol Type { get; }
 
+        /// <summary>
+        /// The declared nullability of this local
+        /// </summary>
+        Nullability Nullability { get; }
+
         /// <summary>
         /// Returns true if this local variable was declared as "const" (i.e. is a constant declaration).
         /// Also returns true for an enum member.

src/Compilers/Core/Portable/Symbols/IMethodSymbol.cs

@@ -90,13 +90,24 @@ public interface IMethodSymbol : ISymbol
         /// </summary>
         ITypeSymbol ReturnType { get; }
 
+        /// <summary>
+        /// The nullability of the return of the method.
+        /// </summary>
+        Nullability ReturnNullability { get; }
+
         /// <summary>
         /// Returns the type arguments that have been substituted for the type parameters. 
         /// If nothing has been substituted for a given type parameter,
         /// then the type parameter itself is consider the type argument.
         /// </summary>
         ImmutableArray<ITypeSymbol> TypeArguments { get; }
 
+        /// <summary>
+        /// Returns the nullablities of the type arguments that have been subsituted for the
+        /// type parameters.
+        /// </summary>
+        ImmutableArray<Nullability> TypeArgumentsNullabilities { get; }
+
         /// <summary>
         /// Get the type parameters on this method. If the method has not generic,
         /// returns an empty list.
@@ -135,6 +146,12 @@ public interface IMethodSymbol : ISymbol
         /// </summary>
         ITypeSymbol ReceiverType { get; }
 
+        /// <summary>
+        /// If this method can be applied to an object, returns the nullability of the object it is
+        /// applied to.
+        /// </summary>
+        Nullability ReceiverNullability { get; }
+
         /// <summary>
         /// If this method is a reduced extension method, returns the definition of extension
         /// method from which this was reduced. Otherwise, returns null.

src/Compilers/Core/Portable/Symbols/IParameterSymbol.cs

@@ -40,6 +40,11 @@ public interface IParameterSymbol : ISymbol
         /// </summary>
         ITypeSymbol Type { get; }
 
+        /// <summary>
+        /// Gets the nullability of the parameter.
+        /// </summary>
+        Nullability Nullability { get; }
+
         /// <summary>
         /// Custom modifiers associated with the parameter type, or an empty array if there are none.
         /// </summary>