Annotate more public syntax APIs

src/Compilers/CSharp/Portable/Symbols/Attributes/AttributeData.cs

@@ -387,6 +387,7 @@ private DeclarativeSecurityAction DecodeSecurityAction(TypedConstant typedValue,
         {
             Debug.Assert((object)targetSymbol != null);
             Debug.Assert(targetSymbol.Kind == SymbolKind.Assembly || targetSymbol.Kind == SymbolKind.NamedType || targetSymbol.Kind == SymbolKind.Method);
+            Debug.Assert(typedValue.ValueInternal is object);
 
             int securityAction = (int)typedValue.ValueInternal;
             bool isPermissionRequestAction;
@@ -527,6 +528,7 @@ private static Location GetSecurityAttributeActionSyntaxLocation(AttributeSyntax
                     PermissionSetAttributeTypeHasRequiredProperty(attrType, filePropName))
                 {
                     // resolve file prop path
+                    Debug.Assert(namedArg.Value.ValueInternal is object);
                     var fileName = (string)namedArg.Value.ValueInternal;
                     var resolver = compilation.Options.XmlReferenceResolver;
 
@@ -535,7 +537,7 @@ private static Location GetSecurityAttributeActionSyntaxLocation(AttributeSyntax
                     if (resolvedFilePath == null)
                     {
                         // CS7053: Unable to resolve file path '{0}' specified for the named argument '{1}' for PermissionSet attribute
-                        Location argSyntaxLocation = nodeOpt != null ? nodeOpt.GetNamedArgumentSyntax(filePropName).Location : NoLocation.Singleton;
+                        Location argSyntaxLocation = nodeOpt?.GetNamedArgumentSyntax(filePropName)?.Location ?? NoLocation.Singleton;
                         diagnostics.Add(ErrorCode.ERR_PermissionSetAttributeInvalidFile, argSyntaxLocation, fileName ?? "<null>", filePropName);
                     }
                     else if (!PermissionSetAttributeTypeHasRequiredProperty(attrType, hexPropName))
@@ -629,7 +631,8 @@ internal string DecodeGuidAttribute(AttributeSyntax? nodeOpt, DiagnosticBag diag
         {
             Debug.Assert(!this.HasErrors);
 
-            var guidString = (string)this.CommonConstructorArguments[0].ValueInternal;
+            Debug.Assert(this.CommonConstructorArguments[0].ValueInternal is object);
+            var guidString = (string)this.CommonConstructorArguments[0].ValueInternal!;
 
             // Native compiler allows only a specific GUID format: "D" format (32 digits separated by hyphens)
             Guid guid;

src/Compilers/CSharp/Portable/Symbols/TypedConstantExtensions.cs

@@ -2,25 +2,20 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
-using System.Collections.Generic;
-using System.Collections.Immutable;
+#nullable enable
+
 using System.Diagnostics;
 using System.Linq;
 using System.Text;
-using Microsoft.CodeAnalysis.Collections;
-using Microsoft.CodeAnalysis.CSharp.Symbols;
-using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.PooledObjects;
-using Microsoft.CodeAnalysis.Text;
-using Roslyn.Utilities;
 
 namespace Microsoft.CodeAnalysis.CSharp
 {
     public static class TypedConstantExtensions
     {
         /// <summary>
         /// Returns the System.String that represents the current TypedConstant.
+        /// For testing and debugging only
         /// </summary>
         /// <returns>A System.String that represents the current TypedConstant.</returns>
         public static string ToCSharpString(this TypedConstant constant)
@@ -37,6 +32,7 @@ public static string ToCSharpString(this TypedConstant constant)
 
             if (constant.Kind == TypedConstantKind.Type || constant.TypeInternal.SpecialType == SpecialType.System_Object)
             {
+                Debug.Assert(constant.Value is object);
                 return "typeof(" + constant.Value.ToString() + ")";
             }
 
@@ -46,6 +42,7 @@ public static string ToCSharpString(this TypedConstant constant)
                 return DisplayEnumConstant(constant);
             }
 
+            Debug.Assert(constant.ValueInternal is object);
             return SymbolDisplay.FormatPrimitive(constant.ValueInternal, quoteStrings: true, useHexadecimalNumbers: false);
         }
 
@@ -55,7 +52,8 @@ private static string DisplayEnumConstant(TypedConstant constant)
             Debug.Assert(constant.Kind == TypedConstantKind.Enum);
 
             // Create a ConstantValue of enum underlying type
-            SpecialType splType = ((INamedTypeSymbol)constant.Type).EnumUnderlyingType.SpecialType;
+            SpecialType splType = ((INamedTypeSymbol)constant.Type).EnumUnderlyingType!.SpecialType;
+            Debug.Assert(constant.ValueInternal is object);
             ConstantValue valueConstant = ConstantValue.Create(constant.ValueInternal, splType);
 
             string typeName = constant.Type.ToDisplayString(SymbolDisplayFormat.QualifiedNameOnlyFormat);
@@ -78,18 +76,18 @@ private static string DisplayUnsignedEnumConstant(TypedConstant constant, Specia
             ulong curValue = 0;
 
             // Initialize the value string to empty
-            PooledStringBuilder pooledBuilder = null;
-            StringBuilder valueStringBuilder = null;
+            PooledStringBuilder? pooledBuilder = null;
+            StringBuilder? valueStringBuilder = null;
 
             // Iterate through all the constant members in the enum type
             var members = constant.Type.GetMembers();
             foreach (var member in members)
             {
                 var field = member as IFieldSymbol;
 
-                if ((object)field != null && field.HasConstantValue)
+                if (field is object && field.HasConstantValue)
                 {
-                    ConstantValue memberConstant = ConstantValue.Create(field.ConstantValue, specialType);
+                    ConstantValue memberConstant = ConstantValue.Create(field.ConstantValue!, specialType); // use MemberNotNull when available https://github.com/dotnet/roslyn/issues/41964
                     ulong memberValue = memberConstant.UInt64Value;
 
                     // Do we have an exact matching enum field
@@ -140,7 +138,10 @@ private static string DisplayUnsignedEnumConstant(TypedConstant constant, Specia
             }
 
             // Unable to decode the enum constant, just display the integral value
-            return constant.ValueInternal.ToString();
+            Debug.Assert(constant.ValueInternal is object);
+            var result = constant.ValueInternal.ToString();
+            Debug.Assert(result is object);
+            return result;
         }
 
         private static string DisplaySignedEnumConstant(TypedConstant constant, SpecialType specialType, long constantToDecode, string typeName)
@@ -152,17 +153,17 @@ private static string DisplaySignedEnumConstant(TypedConstant constant, SpecialT
             long curValue = 0;
 
             // Initialize the value string to empty
-            PooledStringBuilder pooledBuilder = null;
-            StringBuilder valueStringBuilder = null;
+            PooledStringBuilder? pooledBuilder = null;
+            StringBuilder? valueStringBuilder = null;
 
             // Iterate through all the constant members in the enum type
             var members = constant.Type.GetMembers();
             foreach (var member in members)
             {
                 var field = member as IFieldSymbol;
-                if ((object)field != null && field.HasConstantValue)
+                if (field is object && field.HasConstantValue)
                 {
-                    ConstantValue memberConstant = ConstantValue.Create(field.ConstantValue, specialType);
+                    ConstantValue memberConstant = ConstantValue.Create(field.ConstantValue!, specialType); // use MemberNotNull when available https://github.com/dotnet/roslyn/issues/41964 
                     long memberValue = memberConstant.Int64Value;
 
                     // Do we have an exact matching enum field
@@ -213,7 +214,10 @@ private static string DisplaySignedEnumConstant(TypedConstant constant, SpecialT
             }
 
             // Unable to decode the enum constant, just display the integral value
-            return constant.ValueInternal.ToString();
+            Debug.Assert(constant.ValueInternal is object);
+            var result = constant.ValueInternal.ToString();
+            Debug.Assert(result is object);
+            return result;
         }
     }
 }

src/Compilers/CSharp/Portable/Syntax/AliasedQualifiedNameSyntax.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 namespace Microsoft.CodeAnalysis.CSharp.Syntax
 {
     public sealed partial class AliasQualifiedNameSyntax : NameSyntax

src/Compilers/CSharp/Portable/Syntax/AnonymousFunctionExpressionSyntax.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 namespace Microsoft.CodeAnalysis.CSharp.Syntax
 {
     public partial class AnonymousFunctionExpressionSyntax
@@ -10,7 +12,7 @@ public partial class AnonymousFunctionExpressionSyntax
         /// Either the <see cref="Block"/> if it is not <c>null</c> or the
         /// <see cref="ExpressionBody"/> otherwise.
         /// </summary>
-        public CSharpSyntaxNode Body => Block ?? (CSharpSyntaxNode)ExpressionBody;
+        public CSharpSyntaxNode Body => Block ?? (CSharpSyntaxNode)ExpressionBody!;
 
         public AnonymousFunctionExpressionSyntax WithBody(CSharpSyntaxNode body)
             => body is BlockSyntax block

src/Compilers/CSharp/Portable/Syntax/ArgumentSyntax.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 using System.ComponentModel;
 
 namespace Microsoft.CodeAnalysis.CSharp.Syntax

src/Compilers/CSharp/Portable/Syntax/ArrayRankSpecifierSyntax.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 namespace Microsoft.CodeAnalysis.CSharp.Syntax
 {
     public partial class ArrayRankSpecifierSyntax

src/Compilers/CSharp/Portable/Syntax/AttributeSyntax.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 using System;
 using System.Diagnostics;
 
@@ -20,7 +22,7 @@ internal string GetErrorDisplayName()
             return Name.ErrorDisplayName();
         }
 
-        internal AttributeArgumentSyntax GetNamedArgumentSyntax(string namedArgName)
+        internal AttributeArgumentSyntax? GetNamedArgumentSyntax(string namedArgName)
         {
             Debug.Assert(!String.IsNullOrEmpty(namedArgName));
 

src/Compilers/CSharp/Portable/Syntax/AttributeTargetSpecifierSyntax.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 using Microsoft.CodeAnalysis.CSharp.Symbols;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.Text;

src/Compilers/CSharp/Portable/Syntax/BlockSyntax.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 
 namespace Microsoft.CodeAnalysis.CSharp.Syntax

src/Compilers/CSharp/Portable/Syntax/BreakStatementSyntax.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 
 namespace Microsoft.CodeAnalysis.CSharp.Syntax

src/Compilers/CSharp/Portable/Syntax/CSharpLineDirectiveMap.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 using System.Diagnostics;
 using Microsoft.CodeAnalysis.Text;
 using Roslyn.Utilities;
@@ -60,7 +62,7 @@ protected override LineMappingEntry GetEntry(DirectiveTriviaSyntax directiveNode
                         // skip both the mapped line and the filename if the line number is not valid
                         if (!lineToken.ContainsDiagnostics)
                         {
-                            object value = lineToken.Value;
+                            object? value = lineToken.Value;
                             if (value is int)
                             {
                                 // convert one-based line number into zero-based line number
@@ -69,7 +71,7 @@ protected override LineMappingEntry GetEntry(DirectiveTriviaSyntax directiveNode
 
                             if (directive.File.Kind() == SyntaxKind.StringLiteralToken)
                             {
-                                mappedPathOpt = (string)directive.File.Value;
+                                mappedPathOpt = (string?)directive.File.Value;
                             }
 
                             state = PositionState.Remapped;

src/Compilers/CSharp/Portable/Syntax/CSharpPragmaWarningStateMap.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 using System.Collections.Generic;
 using System.Collections.Immutable;
 using System.Diagnostics;
@@ -125,7 +127,7 @@ private static WarningStateMapEntry[] CreatePragmaWarningStateEntries(ArrayBuild
                         if (currentErrorCode.Kind() == SyntaxKind.NumericLiteralExpression)
                         {
                             var token = ((LiteralExpressionSyntax)currentErrorCode).Token;
-                            errorId = MessageProvider.Instance.GetIdForErrorCode((int)token.Value);
+                            errorId = MessageProvider.Instance.GetIdForErrorCode((int)token.Value!);
                         }
                         else if (currentErrorCode.Kind() == SyntaxKind.IdentifierName)
                         {

src/Compilers/CSharp/Portable/Syntax/CSharpSyntaxNode.cs

@@ -520,7 +520,7 @@ protected internal override SyntaxNode InsertTriviaInListCore(SyntaxTrivia origi
             return SyntaxReplacer.InsertTriviaInList(this, originalTrivia, newTrivia, insertBefore).AsRootOfNewTreeWithOptionsFrom(this.SyntaxTree);
         }
 
-        protected internal override SyntaxNode RemoveNodesCore(IEnumerable<SyntaxNode> nodes, SyntaxRemoveOptions options)
+        protected internal override SyntaxNode? RemoveNodesCore(IEnumerable<SyntaxNode> nodes, SyntaxRemoveOptions options)
         {
             return SyntaxNodeRemover.RemoveNodes(this, nodes.Cast<CSharpSyntaxNode>(), options).AsRootOfNewTreeWithOptionsFrom(this.SyntaxTree);
         }

src/Compilers/CSharp/Portable/Syntax/CSharpSyntaxRewriter.cs

@@ -6,6 +6,7 @@
 
 using System;
 using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.Syntax;
 
@@ -31,6 +32,7 @@ public virtual bool VisitIntoStructuredTrivia
 
         private int _recursionDepth;
 
+        [return: NotNullIfNotNull("node")]
         public override SyntaxNode? Visit(SyntaxNode? node)
         {
             if (node != null)

src/Compilers/CSharp/Portable/Syntax/CSharpSyntaxTree.Dummy.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 using System;
 using System.Collections.Immutable;
 using System.Text;

src/Compilers/CSharp/Portable/Syntax/CSharpSyntaxTree.ParsedSyntaxTree.cs

@@ -2,10 +2,13 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 using System;
 using System.Collections.Generic;
 using System.Collections.Immutable;
 using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 using System.Text;
 using System.Threading;
@@ -22,20 +25,20 @@ private class ParsedSyntaxTree : CSharpSyntaxTree
             private readonly string _path;
             private readonly CSharpSyntaxNode _root;
             private readonly bool _hasCompilationUnitRoot;
-            private readonly Encoding _encodingOpt;
+            private readonly Encoding? _encodingOpt;
             private readonly SourceHashAlgorithm _checksumAlgorithm;
             private readonly ImmutableDictionary<string, ReportDiagnostic> _diagnosticOptions;
-            private SourceText _lazyText;
+            private SourceText? _lazyText;
 
             internal ParsedSyntaxTree(
-                SourceText textOpt,
-                Encoding encodingOpt,
+                SourceText? textOpt,
+                Encoding? encodingOpt,
                 SourceHashAlgorithm checksumAlgorithm,
                 string path,
                 CSharpParseOptions options,
                 CSharpSyntaxNode root,
                 Syntax.InternalSyntax.DirectiveStack directives,
-                ImmutableDictionary<string, ReportDiagnostic> diagnosticOptions,
+                ImmutableDictionary<string, ReportDiagnostic>? diagnosticOptions,
                 bool? isGeneratedCode,
                 bool cloneRoot)
             {
@@ -75,13 +78,13 @@ public override SourceText GetText(CancellationToken cancellationToken)
                 return _lazyText;
             }
 
-            public override bool TryGetText(out SourceText text)
+            public override bool TryGetText([NotNullWhen(true)] out SourceText? text)
             {
                 text = _lazyText;
                 return text != null;
             }
 
-            public override Encoding Encoding
+            public override Encoding? Encoding
             {
                 get { return _encodingOpt; }
             }
@@ -133,7 +136,7 @@ public override SyntaxTree WithRootAndOptions(SyntaxNode root, ParseOptions opti
                 }
 
                 return new ParsedSyntaxTree(
-                    null,
+                    textOpt: null,
                     _encodingOpt,
                     _checksumAlgorithm,
                     _path,