PR feedback

Add null checks
Inline "task-like" check

src/Analyzers/CSharp/Analysis/UseAsyncAwaitAnalyzer.cs

@@ -55,7 +55,8 @@ private static void AnalyzeMethodDeclaration(SyntaxNodeAnalysisContext context)
         if (!body.Statements.Any())
             return;
 
-        IMethodSymbol methodSymbol = context.SemanticModel.GetDeclaredSymbol(methodDeclaration, context.CancellationToken);
+        if (context.SemanticModel.GetDeclaredSymbol(methodDeclaration, context.CancellationToken) is not IMethodSymbol methodSymbol)
+            return;
 
         if (!methodSymbol.ReturnType.IsAwaitableTaskType(context.SemanticModel, body.SpanStart))
             return;
@@ -79,7 +80,8 @@ private static void AnalyzeLocalFunctionStatement(SyntaxNodeAnalysisContext cont
         if (!body.Statements.Any())
             return;
 
-        IMethodSymbol methodSymbol = context.SemanticModel.GetDeclaredSymbol(localFunction, context.CancellationToken);
+        if (context.SemanticModel.GetDeclaredSymbol(localFunction, context.CancellationToken) is not IMethodSymbol methodSymbol)
+            return;
 
         if (!methodSymbol.ReturnType.IsAwaitableTaskType(context.SemanticModel, body.SpanStart))
             return;

src/Core/SymbolUtility.cs

@@ -650,6 +650,11 @@ public static bool IsAwaitable(this ISymbol? symbol, SemanticModel semanticModel
         if (typeSymbol.IsWellKnownTaskType())
             return true;
 
+        return HasAwaitableShape(typeSymbol, semanticModel, position);
+    }
+
+    private static bool HasAwaitableShape(ITypeSymbol typeSymbol, SemanticModel semanticModel, int position)
+    {
         // this is the same check as in Roslyn, reimplemented due to it being internal
         // https://github.com/dotnet/roslyn/blob/a182892bf997a457cfcdbece5352e1a139eb2a12/src/Compilers/CSharp/Portable/Binder/Binder_Await.cs#L281-L289
 
@@ -711,50 +716,34 @@ public static bool IsAwaitable(this ISymbol? symbol, SemanticModel semanticModel
     }
 
     /// <summary>
-    /// Determines if the type is a task type - that is, <see cref="Task"/>, <see cref="Task{TResult}"/>, or a <see href="https://github.com/dotnet/roslyn/blob/main/docs/features/task-types.md">task-like type</see>.<br/>
-    /// Only task types (and <see langword="void"/>) can be the return type of a method marked with the <see langword="async"/> keyword.
+    /// Determines if a type:
+    /// <list type="bullet">
+    /// <item>
+    /// Is a task type - that is, <see cref="Task"/>, <see cref="Task{TResult}"/>, <see cref="ValueTask"/>, <see cref="ValueTask{TResult}"/>, or a user-implemented <see href="https://github.com/dotnet/roslyn/blob/main/docs/features/task-types.md">task-like type</see>.<br/>
+    /// Only task types (and <see langword="void"/>) can be the return type of an <see langword="async"/> method.
+    /// </item>
+    /// <item>Can be awaited with the <see langword="await"/> keyword (see <see cref="IsAwaitable"/>).</item>
+    /// </list>
     /// </summary>
     /// <remarks>
-    /// For more information, see the <see href="https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/language-specification/classes#15151-general">C# language specification</see>.
+    /// For more information on task types, see the <see href="https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/language-specification/classes#15151-general">C# language specification</see>.
     /// </remarks>
-    /// <returns>A <see cref="bool"/> indicating whether the type is <see cref="Task"/>, <see cref="Task{TResult}"/>, or a <see href="https://github.com/dotnet/roslyn/blob/main/docs/features/task-types.md">task-like type</see>.</returns>
-    public static bool IsTaskLikeType(this ITypeSymbol typeSymbol)
+    public static bool IsAwaitableTaskType(this ITypeSymbol typeSymbol, SemanticModel semanticModel, int position)
     {
         if (typeSymbol.OriginalDefinition is not INamedTypeSymbol definition)
             return false;
 
-        // Task (and Task<T>) are hardcoded and don't have an AsyncMethodBuilder attribute.
-        // Their descendants, however, are not, and go through the rest of the checks.
-        // (see https://github.com/dotnet/roslyn/blob/c4203b867e9c0287cabb0a0674bfca096c08fd3e/src/Compilers/CSharp/Portable/Symbols/TypeSymbolExtensions.cs#L1778-L1806 )
-        if (definition.HasMetadataName(in MetadataNames.System_Threading_Tasks_Task)
-            || definition.HasMetadataName(in MetadataNames.System_Threading_Tasks_Task_T))
-        {
+        if (definition.IsWellKnownTaskType())
             return true;
-        }
 
         // Roslyn checks arity, see https://github.com/dotnet/roslyn/blob/c4203b867e9c0287cabb0a0674bfca096c08fd3e/src/Compilers/CSharp/Portable/Symbols/TypeSymbolExtensions.cs#L1844
-        return definition.Arity <= 1
-            && definition.HasAttribute(in MetadataNames.System_Runtime_CompilerServices_AsyncMethodBuilderAttribute);
-    }
-
-    /// <summary>
-    /// <para>
-    /// Combines <see cref="IsTaskLikeType"/> and <see cref="IsAwaitable"/>.
-    /// </para>
-    /// In short, this determines if a type:
-    /// <list type="bullet">
-    /// <item>Can be the return type of an <see langword="async"/> method;</item>
-    /// <item>Can be awaited with the <see langword="await"/> keyword.</item>
-    /// </list>
-    /// </summary>
-    public static bool IsAwaitableTaskType(this ITypeSymbol typeSymbol, SemanticModel semanticModel, int position)
-    {
-        if (typeSymbol.OriginalDefinition is not INamedTypeSymbol definition)
+        if (definition.Arity > 1)
             return false;
 
-        if (definition.IsWellKnownTaskType())
-            return true;
+        // Task (and Task<T>) are hardcoded and don't have an AsyncMethodBuilder attribute.
+        // see https://github.com/dotnet/roslyn/blob/c4203b867e9c0287cabb0a0674bfca096c08fd3e/src/Compilers/CSharp/Portable/Symbols/TypeSymbolExtensions.cs#L1778-L1806
+        bool isTaskLike = definition.HasAttribute(in MetadataNames.System_Runtime_CompilerServices_AsyncMethodBuilderAttribute);
 
-        return IsTaskLikeType(definition) && IsAwaitable(definition, semanticModel, position);
+        return isTaskLike && HasAwaitableShape(definition, semanticModel, position);
     }
 }