Add "IsWrittenTo" from Roslyn (#8947)

analyzers/src/SonarAnalyzer.CSharp/Extensions/ExpressionSyntaxExtensions.Roslyn.cs

@@ -0,0 +1,278 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// 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.Diagnostics.CodeAnalysis;
+
+namespace Microsoft.CodeAnalysis.CSharp.Extensions;
+
+// Copied from Roslyn
+// https://github.com/dotnet/roslyn/blob/575bc42589145ba18b4f1cc2267d02695f861d8f/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/CSharp/Extensions/ExpressionSyntaxExtensions.cs
+[ExcludeFromCodeCoverage]
+public static class ExpressionSyntaxExtensions
+{
+    /// <summary>
+    /// Returns <see langword="true"/> if <paramref name="expression"/> represents a node where a value is written to, like on the left side of an assignment expression. This method
+    /// also returns <see langword="true"/> for potentially writeable expressions, like <see langword="ref"/> parameters.
+    /// See also <seealso cref="IsOnlyWrittenTo(ExpressionSyntax)"/>.
+    /// </summary>
+    /// <remarks>
+    /// Copied from <seealso href="https://github.com/dotnet/roslyn/blob/575bc42589145ba18b4f1cc2267d02695f861d8f/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/CSharp/Extensions/ExpressionSyntaxExtensions.cs#L319"/>
+    /// </remarks>
+    public static bool IsWrittenTo(
+        this ExpressionSyntax expression,
+        SemanticModel semanticModel,
+        CancellationToken cancellationToken)
+    {
+        if (expression == null)
+            return false;
+
+        expression = GetExpressionToAnalyzeForWrites(expression);
+
+        if (expression.IsOnlyWrittenTo())
+            return true;
+
+        if (expression.IsInRefContext(out var refParent))
+        {
+            // most cases of `ref x` will count as a potential write of `x`.  An important exception is:
+            // `ref readonly y = ref x`.  In that case, because 'y' can't be written to, this would not
+            // be a write of 'x'.
+            if (refParent.Parent is EqualsValueClauseSyntax { Parent: VariableDeclaratorSyntax { Parent: VariableDeclarationSyntax { Type: { } variableDeclarationType } } })
+            {
+                if (ScopedTypeSyntaxWrapper.IsInstance(variableDeclarationType) && (ScopedTypeSyntaxWrapper)variableDeclarationType is { } scopedType)
+                {
+                    variableDeclarationType = scopedType.Type;
+                }
+
+                if (RefTypeSyntaxWrapper.IsInstance(variableDeclarationType) && ((RefTypeSyntaxWrapper)variableDeclarationType).ReadOnlyKeyword != default)
+                {
+                    return false;
+                }
+            }
+
+            return true;
+        }
+
+        // Similar to `ref x`, `&x` allows reads and write of the value, meaning `x` may be (but is not definitely)
+        // written to.
+        if (expression.Parent.IsKind(SyntaxKind.AddressOfExpression))
+            return true;
+
+        // We're written if we're used in a ++, or -- expression.
+        if (expression.IsOperandOfIncrementOrDecrementExpression())
+            return true;
+
+        if (expression.IsLeftSideOfAnyAssignExpression())
+            return true;
+
+        // An extension method invocation with a ref-this parameter can write to an expression.
+        if (expression.Parent is MemberAccessExpressionSyntax memberAccess &&
+            expression == memberAccess.Expression)
+        {
+            var symbol = semanticModel.GetSymbolInfo(memberAccess, cancellationToken).Symbol;
+            if (symbol is IMethodSymbol
+                {
+                    MethodKind: MethodKind.ReducedExtension,
+                    ReducedFrom.Parameters: { Length: > 0 } parameters,
+                } && parameters[0].RefKind == RefKind.Ref)
+            {
+                return true;
+            }
+        }
+
+        return false;
+    }
+
+    // Copy of
+    // https://github.com/dotnet/roslyn/blob/575bc42589145ba18b4f1cc2267d02695f861d8f/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/CSharp/Extensions/ExpressionSyntaxExtensions.cs#L221
+    private static ExpressionSyntax GetExpressionToAnalyzeForWrites(ExpressionSyntax? expression)
+    {
+        if (expression.IsRightSideOfDotOrArrow())
+        {
+            expression = (ExpressionSyntax)expression.Parent;
+        }
+
+        expression = (ExpressionSyntax)expression.WalkUpParentheses();
+
+        return expression;
+    }
+
+    // Copy of
+    // https://github.com/dotnet/roslyn/blob/575bc42589145ba18b4f1cc2267d02695f861d8f/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/CSharp/Extensions/ExpressionSyntaxExtensions.cs#L63
+    public static bool IsRightSideOfDotOrArrow(this ExpressionSyntax name)
+        => IsAnyMemberAccessExpressionName(name) || IsRightSideOfQualifiedName(name);
+
+    // Copy of
+    // https://github.com/dotnet/roslyn/blob/575bc42589145ba18b4f1cc2267d02695f861d8f/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/CSharp/Extensions/ExpressionSyntaxExtensions.cs#L41
+    public static bool IsAnyMemberAccessExpressionName(this ExpressionSyntax expression)
+    {
+        if (expression == null)
+            return false;
+
+        return expression == (expression.Parent as MemberAccessExpressionSyntax)?.Name ||
+            expression.IsMemberBindingExpressionName();
+    }
+
+    // Copy of
+    // https://github.com/dotnet/roslyn/blob/575bc42589145ba18b4f1cc2267d02695f861d8f/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/CSharp/Extensions/ExpressionSyntaxExtensions.cs#L50
+    public static bool IsMemberBindingExpressionName(this ExpressionSyntax expression)
+        => expression?.Parent is MemberBindingExpressionSyntax memberBinding &&
+           memberBinding.Name == expression;
+
+    // Copy of
+    // https://github.com/dotnet/roslyn/blob/575bc42589145ba18b4f1cc2267d02695f861d8f/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/CSharp/Extensions/ExpressionSyntaxExtensions.cs#L54
+    public static bool IsRightSideOfQualifiedName(this ExpressionSyntax expression)
+        => expression?.Parent is QualifiedNameSyntax qualifiedName && qualifiedName.Right == expression;
+
+    // Copy of
+    // https://github.com/dotnet/roslyn/blob/575bc42589145ba18b4f1cc2267d02695f861d8f/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/CSharp/Extensions/ExpressionSyntaxExtensions.cs#L233
+    public static bool IsOnlyWrittenTo(this ExpressionSyntax expression)
+    {
+        expression = GetExpressionToAnalyzeForWrites(expression);
+
+        if (expression != null)
+        {
+            if (expression.IsInOutContext())
+            {
+                return true;
+            }
+
+            if (expression.Parent != null)
+            {
+                if (expression.IsLeftSideOfAssignExpression())
+                {
+                    return true;
+                }
+
+                if (expression.IsAttributeNamedArgumentIdentifier())
+                {
+                    return true;
+                }
+            }
+
+            if (IsExpressionOfArgumentInDeconstruction(expression))
+            {
+                return true;
+            }
+        }
+
+        return false;
+    }
+
+    /// <summary>
+    /// If this declaration or identifier is part of a deconstruction, find the deconstruction.
+    /// If found, returns either an assignment expression or a foreach variable statement.
+    /// Returns null otherwise.
+    ///
+    /// copied from SyntaxExtensions.GetContainingDeconstruction.
+    /// </summary>
+    /// <remarks>
+    /// Copied from <seealso href="https://github.com/dotnet/roslyn/blob/575bc42589145ba18b4f1cc2267d02695f861d8f/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/CSharp/Extensions/ExpressionSyntaxExtensions.cs#L273"/>
+    /// </remarks>
+    private static bool IsExpressionOfArgumentInDeconstruction(ExpressionSyntax expr)
+    {
+        if (!expr.IsParentKind(SyntaxKind.Argument))
+        {
+            return false;
+        }
+
+        while (true)
+        {
+            var parent = expr.Parent;
+            if (parent == null)
+            {
+                return false;
+            }
+
+            switch (parent.Kind())
+            {
+                case SyntaxKind.Argument:
+                    if (parent.Parent?.Kind() == SyntaxKindEx.TupleExpression)
+                    {
+                        expr = (ExpressionSyntax)parent.Parent;
+                        continue;
+                    }
+
+                    return false;
+                case SyntaxKind.SimpleAssignmentExpression:
+                    if (((AssignmentExpressionSyntax)parent).Left == expr)
+                    {
+                        return true;
+                    }
+
+                    return false;
+                case SyntaxKindEx.ForEachVariableStatement:
+                    if (((ForEachVariableStatementSyntaxWrapper)parent).Variable == expr)
+                    {
+                        return true;
+                    }
+
+                    return false;
+
+                default:
+                    return false;
+            }
+        }
+    }
+
+    // https://github.com/dotnet/roslyn/blob/575bc42589145ba18b4f1cc2267d02695f861d8f/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/CSharp/Extensions/ExpressionSyntaxExtensions.cs#L190
+    public static bool IsInOutContext(this ExpressionSyntax expression)
+        => expression?.Parent is ArgumentSyntax { RefOrOutKeyword: SyntaxToken { RawKind: (int)SyntaxKind.OutKeyword } } argument &&
+           argument.Expression == expression;
+
+    // https://github.com/dotnet/roslyn/blob/575bc42589145ba18b4f1cc2267d02695f861d8f/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/CSharp/Extensions/ExpressionSyntaxExtensions.cs#L383
+    public static bool IsAttributeNamedArgumentIdentifier(this ExpressionSyntax expression)
+    {
+        var nameEquals = expression?.Parent as NameEqualsSyntax;
+        return nameEquals.IsParentKind(SyntaxKind.AttributeArgument);
+    }
+
+    // https://github.com/dotnet/roslyn/blob/575bc42589145ba18b4f1cc2267d02695f861d8f/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/CSharp/Extensions/ExpressionSyntaxExtensions.cs#L194
+    public static bool IsInRefContext(this ExpressionSyntax expression)
+        => IsInRefContext(expression, out _);
+
+    /// <summary>
+    /// Returns true if this expression is in some <c>ref</c> keyword context.  If <see langword="true"/> then
+    /// <paramref name="refParent"/> will be the node containing the <see langword="ref"/> keyword.
+    /// </summary>
+    /// <remarks>
+    /// Copied from <seealso href="https://github.com/dotnet/roslyn/blob/575bc42589145ba18b4f1cc2267d02695f861d8f/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/CSharp/Extensions/ExpressionSyntaxExtensions.cs#L201"/>
+    /// </remarks>
+    public static bool IsInRefContext(this ExpressionSyntax expression, out SyntaxNode refParent)
+    {
+        while (expression?.Parent is ParenthesizedExpressionSyntax or PostfixUnaryExpressionSyntax { RawKind: (int)SyntaxKindEx.SuppressNullableWarningExpression })
+            expression = (ExpressionSyntax)expression.Parent;
+
+        if (expression?.Parent switch
+        {
+            ArgumentSyntax { RefOrOutKeyword.RawKind: (int)SyntaxKind.RefKeyword } => true,
+            var x when RefExpressionSyntaxWrapper.IsInstance(x) => true,
+            _ => false,
+        })
+        {
+            refParent = expression.Parent;
+            return true;
+        }
+
+        refParent = null;
+        return false;
+    }
+
+    // https://github.com/dotnet/roslyn/blob/575bc42589145ba18b4f1cc2267d02695f861d8f/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/CSharp/Extensions/ExpressionSyntaxExtensions.cs#L389
+    public static bool IsOperandOfIncrementOrDecrementExpression(this ExpressionSyntax expression)
+    {
+        if (expression?.Parent is SyntaxNode parent)
+        {
+            switch (parent.Kind())
+            {
+                case SyntaxKind.PostIncrementExpression:
+                case SyntaxKind.PreIncrementExpression:
+                case SyntaxKind.PostDecrementExpression:
+                case SyntaxKind.PreDecrementExpression:
+                    return true;
+            }
+        }
+
+        return false;
+    }
+}