Fixup quick info for suppressed nullable operations.

src/EditorFeatures/CSharpTest/QuickInfo/SemanticQuickInfoSourceTests.cs

@@ -6997,6 +6997,40 @@ void N(string? s)
             MainDescription($"({FeaturesResources.parameter}) string? s"),
             NullabilityAnalysis(string.Format(FeaturesResources._0_may_be_null_here, "s")));
 
+    [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/42543")]
+    public Task NullableParameterThatIsMaybeNull_Suppressed1()
+        => TestWithOptionsAsync(TestOptions.Regular8,
+            """
+            #nullable enable
+
+            class X
+            {
+                void N(string? s)
+                {
+                    string s2 = $$s!;
+                }
+            }
+            """,
+            MainDescription($"({FeaturesResources.parameter}) string? s"),
+            NullabilityAnalysis(string.Format(FeaturesResources._0_may_be_null_here, "s")));
+
+    [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/42543")]
+    public Task NullableParameterThatIsMaybeNull_Suppressed2()
+        => TestWithOptionsAsync(TestOptions.Regular8,
+            """
+            #nullable enable
+
+            class X
+            {
+                void N(string? s)
+                {
+                    string s2 = $$s!!;
+                }
+            }
+            """,
+            MainDescription($"({FeaturesResources.parameter}) string? s"),
+            NullabilityAnalysis(string.Format(FeaturesResources._0_may_be_null_here, "s")));
+
     [Fact]
     public Task NullableParameterThatIsNotNull()
         => TestWithOptionsAsync(TestOptions.Regular8,

src/Features/Core/Portable/LanguageServices/SymbolDisplayService/AbstractSymbolDisplayService.cs

@@ -12,26 +12,12 @@
 
 namespace Microsoft.CodeAnalysis.LanguageService;
 
-internal abstract partial class AbstractSymbolDisplayService : ISymbolDisplayService
+internal abstract partial class AbstractSymbolDisplayService(LanguageServices services) : ISymbolDisplayService
 {
-    protected readonly LanguageServices LanguageServices;
-
-    protected AbstractSymbolDisplayService(LanguageServices services)
-    {
-        LanguageServices = services;
-    }
+    protected readonly LanguageServices LanguageServices = services;
 
     protected abstract AbstractSymbolDescriptionBuilder CreateDescriptionBuilder(SemanticModel semanticModel, int position, SymbolDescriptionOptions options, CancellationToken cancellationToken);
 
-    public Task<string> ToDescriptionStringAsync(SemanticModel semanticModel, int position, ISymbol symbol, SymbolDescriptionOptions options, SymbolDescriptionGroups groups, CancellationToken cancellationToken)
-        => ToDescriptionStringAsync(semanticModel, position, [symbol], options, groups, cancellationToken);
-
-    public async Task<string> ToDescriptionStringAsync(SemanticModel semanticModel, int position, ImmutableArray<ISymbol> symbols, SymbolDescriptionOptions options, SymbolDescriptionGroups groups, CancellationToken cancellationToken)
-    {
-        var parts = await ToDescriptionPartsAsync(semanticModel, position, symbols, options, groups, cancellationToken).ConfigureAwait(false);
-        return parts.ToDisplayString();
-    }
-
     public Task<ImmutableArray<SymbolDisplayPart>> ToDescriptionPartsAsync(SemanticModel semanticModel, int position, ImmutableArray<ISymbol> symbols, SymbolDescriptionOptions options, SymbolDescriptionGroups groups, CancellationToken cancellationToken)
     {
         if (symbols.Length == 0)
@@ -45,9 +31,7 @@ public async Task<IDictionary<SymbolDescriptionGroups, ImmutableArray<TaggedText
         SemanticModel semanticModel, int position, ImmutableArray<ISymbol> symbols, SymbolDescriptionOptions options, CancellationToken cancellationToken)
     {
         if (symbols.Length == 0)
-        {
             return SpecializedCollections.EmptyDictionary<SymbolDescriptionGroups, ImmutableArray<TaggedText>>();
-        }
 
         var builder = CreateDescriptionBuilder(semanticModel, position, options, cancellationToken);
         return await builder.BuildDescriptionSectionsAsync(symbols).ConfigureAwait(false);

src/Features/Core/Portable/LanguageServices/SymbolDisplayService/ISymbolDisplayService.cs

@@ -12,8 +12,21 @@ namespace Microsoft.CodeAnalysis.LanguageService;
 
 internal interface ISymbolDisplayService : ILanguageService
 {
-    Task<string> ToDescriptionStringAsync(SemanticModel semanticModel, int position, ISymbol symbol, SymbolDescriptionOptions options, SymbolDescriptionGroups groups = SymbolDescriptionGroups.All, CancellationToken cancellationToken = default);
-    Task<string> ToDescriptionStringAsync(SemanticModel semanticModel, int position, ImmutableArray<ISymbol> symbols, SymbolDescriptionOptions options, SymbolDescriptionGroups groups = SymbolDescriptionGroups.All, CancellationToken cancellationToken = default);
     Task<ImmutableArray<SymbolDisplayPart>> ToDescriptionPartsAsync(SemanticModel semanticModel, int position, ImmutableArray<ISymbol> symbols, SymbolDescriptionOptions options, SymbolDescriptionGroups groups = SymbolDescriptionGroups.All, CancellationToken cancellationToken = default);
     Task<IDictionary<SymbolDescriptionGroups, ImmutableArray<TaggedText>>> ToDescriptionGroupsAsync(SemanticModel semanticModel, int position, ImmutableArray<ISymbol> symbols, SymbolDescriptionOptions options, CancellationToken cancellationToken = default);
 }
+
+internal static class ISymbolDisplayServiceExtensions
+{
+    extension(ISymbolDisplayService service)
+    {
+        public Task<string> ToDescriptionStringAsync(SemanticModel semanticModel, int position, ISymbol symbol, SymbolDescriptionOptions options, SymbolDescriptionGroups groups, CancellationToken cancellationToken)
+            => service.ToDescriptionStringAsync(semanticModel, position, [symbol], options, groups, cancellationToken);
+
+        public async Task<string> ToDescriptionStringAsync(SemanticModel semanticModel, int position, ImmutableArray<ISymbol> symbols, SymbolDescriptionOptions options, SymbolDescriptionGroups groups, CancellationToken cancellationToken)
+        {
+            var parts = await service.ToDescriptionPartsAsync(semanticModel, position, symbols, options, groups, cancellationToken).ConfigureAwait(false);
+            return parts.ToDisplayString();
+        }
+    }
+}

src/Features/Core/Portable/QuickInfo/CommonSemanticQuickInfoProvider.cs

@@ -8,10 +8,10 @@
 using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
+using Microsoft.CodeAnalysis.Editing;
 using Microsoft.CodeAnalysis.Host;
 using Microsoft.CodeAnalysis.LanguageService;
 using Microsoft.CodeAnalysis.PooledObjects;
-using Microsoft.CodeAnalysis.Shared.Collections;
 using Microsoft.CodeAnalysis.Shared.Extensions;
 using Microsoft.CodeAnalysis.Shared.Utilities;
 using Roslyn.Utilities;
@@ -20,6 +20,8 @@ namespace Microsoft.CodeAnalysis.QuickInfo;
 
 internal abstract partial class CommonSemanticQuickInfoProvider : CommonQuickInfoProvider
 {
+    private static readonly SyntaxAnnotation s_annotation = new();
+
     protected override async Task<QuickInfoItem?> BuildQuickInfoAsync(
         QuickInfoContext context, SyntaxToken token)
     {
@@ -188,7 +190,77 @@ protected static Task<QuickInfoItem> CreateContentAsync(
 
     protected virtual (NullableAnnotation, NullableFlowState) GetNullabilityAnalysis(SemanticModel semanticModel, ISymbol symbol, SyntaxNode node, CancellationToken cancellationToken) => default;
 
-    private TokenInformation BindToken(
+    private (NullableAnnotation, NullableFlowState) GetNullabilityAnalysis(
+        SolutionServices services, SemanticModel semanticModel, ISymbol symbol, SyntaxToken token, CancellationToken cancellationToken)
+    {
+        var languageServices = services.GetLanguageServices(semanticModel.Language);
+        var syntaxFacts = languageServices.GetRequiredService<ISyntaxFactsService>();
+
+        var bindableParent = syntaxFacts.TryGetBindableParent(token);
+        if (bindableParent is null)
+            return default;
+
+        return TryGetNullabilityAnalysisForSuppressedExpression(out var analysis)
+            ? analysis
+            : GetNullabilityAnalysis(semanticModel, symbol, bindableParent, cancellationToken);
+
+        bool TryGetNullabilityAnalysisForSuppressedExpression(out (NullableAnnotation, NullableFlowState) analysis)
+        {
+            analysis = default;
+
+            // Look to see if we're inside a suppression (e.g. `expr!`).  The suppression changes the nullability analysis,
+            // and we don't actually want that here as we want to show the original nullability prior to the suppression applying.
+            //
+            // In that case, actually fork the semantic model with the `!` removed and then re-bind the token, getting the 
+            // analysis results from that.
+            var tokenParent = token.GetRequiredParent();
+            var parentSuppression = GetOuterSuppression(tokenParent);
+            if (parentSuppression is null)
+                return false;
+
+            var root = semanticModel.SyntaxTree.GetRoot(cancellationToken);
+
+            var editor = new SyntaxEditor(root, services);
+            // First, mark the token, so we can find it later.
+            editor.ReplaceNode(
+                tokenParent, tokenParent.ReplaceToken(token, token.WithAdditionalAnnotations(s_annotation)));
+
+            // Now walk upwards, removing all the suppressions until we hit the top of the suppression chain.
+            for (var currentSuppression = parentSuppression;
+                 currentSuppression is not null;
+                 currentSuppression = GetOuterSuppression(currentSuppression))
+            {
+                editor.ReplaceNode(
+                    currentSuppression,
+                    (current, _) => syntaxFacts.GetOperandOfPostfixUnaryExpression(current));
+            }
+
+            // Now fork the semantic model with the new root that has the suppressions removed.
+            var newRoot = editor.GetChangedRoot();
+
+            var newTree = semanticModel.SyntaxTree.WithRootAndOptions(newRoot, semanticModel.SyntaxTree.Options);
+            var newToken = newTree.GetRoot(cancellationToken).GetAnnotatedTokens(s_annotation).Single();
+
+            var newBindableParent = syntaxFacts.TryGetBindableParent(newToken);
+            if (newBindableParent is null)
+                return false;
+
+            var newCompilation = semanticModel.Compilation.ReplaceSyntaxTree(semanticModel.SyntaxTree, newTree);
+            semanticModel = newCompilation.GetSemanticModel(newTree);
+
+            var symbols = BindSymbols(services, semanticModel, newToken, cancellationToken);
+            if (symbols.IsEmpty)
+                return false;
+
+            analysis = GetNullabilityAnalysis(semanticModel, symbols[0], newBindableParent, cancellationToken);
+            return true;
+
+            SyntaxNode? GetOuterSuppression(SyntaxNode node)
+                => node.Ancestors().FirstOrDefault(a => a.RawKind == syntaxFacts.SyntaxKinds.SuppressNullableWarningExpression);
+        }
+    }
+
+    protected ImmutableArray<ISymbol> BindSymbols(
         SolutionServices services, SemanticModel semanticModel, SyntaxToken token, CancellationToken cancellationToken)
     {
         var languageServices = services.GetLanguageServices(semanticModel.Language);
@@ -203,14 +275,39 @@ private TokenInformation BindToken(
         AddSymbols(GetSymbolsFromToken(token, services, semanticModel, cancellationToken), checkAccessibility: true);
         AddSymbols(bindableParent != null ? semanticModel.GetMemberGroup(bindableParent, cancellationToken) : [], checkAccessibility: false);
 
+        return filteredSymbols.ToImmutableAndClear();
+
+        void AddSymbols(ImmutableArray<ISymbol> symbols, bool checkAccessibility)
+        {
+            foreach (var symbol in symbols)
+            {
+                if (!IsOk(symbol))
+                    continue;
+
+                if (checkAccessibility && !IsAccessible(symbol, enclosingType))
+                    continue;
+
+                if (symbolSet.Add(symbol))
+                    filteredSymbols.Add(symbol);
+            }
+        }
+    }
+
+    private TokenInformation BindToken(
+        SolutionServices services, SemanticModel semanticModel, SyntaxToken token, CancellationToken cancellationToken)
+    {
+        var filteredSymbols = BindSymbols(services, semanticModel, token, cancellationToken);
+
+        var languageServices = services.GetLanguageServices(semanticModel.Language);
+        var syntaxFacts = languageServices.GetRequiredService<ISyntaxFactsService>();
+
         if (filteredSymbols is [var firstSymbol, ..])
         {
             var isAwait = syntaxFacts.IsAwaitKeyword(token);
-            var nullabilityInfo = bindableParent != null
-                ? GetNullabilityAnalysis(semanticModel, firstSymbol, bindableParent, cancellationToken)
-                : default;
+            var nullabilityInfo = GetNullabilityAnalysis(
+                services, semanticModel, firstSymbol, token, cancellationToken);
 
-            return new TokenInformation(filteredSymbols.ToImmutableAndClear(), isAwait, nullabilityInfo);
+            return new TokenInformation(filteredSymbols, isAwait, nullabilityInfo);
         }
 
         // Couldn't bind the token to specific symbols.  If it's an operator, see if we can at
@@ -223,21 +320,6 @@ private TokenInformation BindToken(
         }
 
         return default;
-
-        void AddSymbols(ImmutableArray<ISymbol> symbols, bool checkAccessibility)
-        {
-            foreach (var symbol in symbols)
-            {
-                if (!IsOk(symbol))
-                    continue;
-
-                if (checkAccessibility && !IsAccessible(symbol, enclosingType))
-                    continue;
-
-                if (symbolSet.Add(symbol))
-                    filteredSymbols.Add(symbol);
-            }
-        }
     }
 
     private ImmutableArray<ISymbol> GetSymbolsFromToken(SyntaxToken token, SolutionServices services, SemanticModel semanticModel, CancellationToken cancellationToken)

src/Workspaces/SharedUtilitiesAndExtensions/Compiler/CSharp/Services/SyntaxFacts/CSharpSyntaxFacts.cs

@@ -1665,6 +1665,13 @@ public void GetPartsOfParenthesizedExpression(
         closeParen = parenthesizedExpression.CloseParenToken;
     }
 
+    public void GetPartsOfPostfixUnaryExpression(SyntaxNode node, out SyntaxNode operand, out SyntaxToken operatorToken)
+    {
+        var postfixUnaryExpression = (PostfixUnaryExpressionSyntax)node;
+        operand = postfixUnaryExpression.Operand;
+        operatorToken = postfixUnaryExpression.OperatorToken;
+    }
+
     public void GetPartsOfPrefixUnaryExpression(SyntaxNode node, out SyntaxToken operatorToken, out SyntaxNode operand)
     {
         var prefixUnaryExpression = (PrefixUnaryExpressionSyntax)node;

src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Services/SyntaxFacts/ISyntaxFacts.cs

@@ -34,7 +34,7 @@ namespace Microsoft.CodeAnalysis.LanguageService;
 /// </item>
 /// <item>
 /// 'GetXxxOfYYY' where 'XXX' matches the name of a property on a 'YYY' syntax construct that both C# and VB have.  For
-/// example 'GetExpressionOfMemberAccessExpression' corresponding to MemberAccessExpressionsyntax.Expression in both C# and
+/// example 'GetExpressionOfMemberAccessExpression' corresponding to MemberAccessExpressionSyntax.Expression in both C# and
 /// VB.  These functions should throw if passed a node that the corresponding 'IsYYY' did not return <see langword="true"/> for.
 /// For nodes that only have a single child, these functions can stay here.  For nodes with multiple children, these should migrate
 /// to <see cref="ISyntaxFactsExtensions"/> and be built off of 'GetPartsOfXXX'.
@@ -537,6 +537,7 @@ void GetPartsOfTupleExpression<TArgumentSyntax>(SyntaxNode node,
     void GetPartsOfImplicitObjectCreationExpression(SyntaxNode node, out SyntaxToken keyword, out SyntaxNode argumentList, out SyntaxNode? initializer);
     void GetPartsOfParameter(SyntaxNode node, out SyntaxToken identifier, out SyntaxNode? @default);
     void GetPartsOfParenthesizedExpression(SyntaxNode node, out SyntaxToken openParen, out SyntaxNode expression, out SyntaxToken closeParen);
+    void GetPartsOfPostfixUnaryExpression(SyntaxNode node, out SyntaxNode operand, out SyntaxToken operatorToken);
     void GetPartsOfPrefixUnaryExpression(SyntaxNode node, out SyntaxToken operatorToken, out SyntaxNode operand);
     void GetPartsOfQualifiedName(SyntaxNode node, out SyntaxNode left, out SyntaxToken dotToken, out SyntaxNode right);
     void GetPartsOfUsingAliasDirective(SyntaxNode node, out SyntaxToken globalKeyword, out SyntaxToken alias, out SyntaxNode name);

src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Services/SyntaxFacts/ISyntaxFactsExtensions.cs

@@ -579,6 +579,12 @@ public static SyntaxNode GetNameOfMemberAccessExpression(this ISyntaxFacts synta
         return name;
     }
 
+    public static SyntaxNode GetOperandOfPostfixUnaryExpression(this ISyntaxFacts syntaxFacts, SyntaxNode node)
+    {
+        syntaxFacts.GetPartsOfPostfixUnaryExpression(node, out var operand, out _);
+        return operand;
+    }
+
     public static SyntaxNode GetOperandOfPrefixUnaryExpression(this ISyntaxFacts syntaxFacts, SyntaxNode node)
     {
         syntaxFacts.GetPartsOfPrefixUnaryExpression(node, out _, out var operand);

src/Workspaces/SharedUtilitiesAndExtensions/Compiler/VisualBasic/Services/SyntaxFacts/VisualBasicSyntaxFacts.vb

@@ -1866,6 +1866,10 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.LanguageService
             closeParen = parenthesizedExpression.CloseParenToken
         End Sub
 
+        Public Sub GetPartsOfPostfixUnaryExpression(node As SyntaxNode, ByRef operand As SyntaxNode, ByRef operatorToken As SyntaxToken) Implements ISyntaxFacts.GetPartsOfPostfixUnaryExpression
+            Throw New InvalidOperationException(DoesNotExistInVBErrorMessage)
+        End Sub
+
         Public Sub GetPartsOfPrefixUnaryExpression(node As SyntaxNode, ByRef operatorToken As SyntaxToken, ByRef operand As SyntaxNode) Implements ISyntaxFacts.GetPartsOfPrefixUnaryExpression
             Dim unaryExpression = DirectCast(node, UnaryExpressionSyntax)
             operatorToken = unaryExpression.OperatorToken