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// 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;
using System.Composition;
using Microsoft.CodeAnalysis.CSharp.Syntax;
using Microsoft.CodeAnalysis.Host.Mef;
using Microsoft.CodeAnalysis.ReassignedVariable;
using Microsoft.CodeAnalysis.Shared.Extensions;
namespace Microsoft.CodeAnalysis.CSharp.ReassignedVariable;
[ExportLanguageService(typeof(IReassignedVariableService), LanguageNames.CSharp), Shared]
[method: ImportingConstructor]
[method: Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
internal sealed class CSharpReassignedVariableService() : AbstractReassignedVariableService<
ParameterSyntax,
VariableDeclaratorSyntax,
SingleVariableDesignationSyntax,
IdentifierNameSyntax>
{
protected override SyntaxToken GetIdentifierOfVariable(VariableDeclaratorSyntax variable)
=> variable.Identifier;
protected override SyntaxToken GetIdentifierOfSingleVariableDesignation(SingleVariableDesignationSyntax variable)
=> variable.Identifier;
protected override bool HasInitializer(SyntaxNode variable)
{
// For regular variable declarators like `var x = 0`
if (variable is VariableDeclaratorSyntax declarator)
return declarator.Initializer != null;
// For deconstruction like `var (b, c) = (0, 0)`, pattern matching like `is var x`, or `out var x`
if (variable is SingleVariableDesignationSyntax designation)
{
// Walk up the tree to find if this is part of an initialized declaration
var current = designation.Parent;
while (current != null)
{
// For out var, the variable is always initialized by the call
if (current is ArgumentSyntax { RefOrOutKeyword.RawKind: (int)SyntaxKind.OutKeyword })
return true;
// For deconstruction assignment like (x, y) = ... or var (x, y) = ...
if (current is AssignmentExpressionSyntax)
return true;
// For foreach (var (x, y) in ...) or similar
if (current is ForEachVariableStatementSyntax)
return true;
// Variables in patterns are always consider assigned by virtue off the pattern itself matching.
if (current is PatternSyntax)
return true;
// Don't search beyond statement boundaries
if (current is StatementSyntax)
break;
current = current.Parent;
}
}
return false;
}
protected override SyntaxNode GetMemberBlock(SyntaxNode methodOrPropertyDeclaration)
=> methodOrPropertyDeclaration;
protected override SyntaxNode GetParentScope(SyntaxNode localDeclaration)
{
var current = localDeclaration;
while (current != null)
{
if (current is BlockSyntax or SwitchSectionSyntax or ArrowExpressionClauseSyntax or AnonymousMethodExpressionSyntax or MemberDeclarationSyntax)
break;
current = current.Parent;
}
Contract.ThrowIfNull(current, "Couldn't find a suitable parent of this local declaration");
return current is GlobalStatementSyntax
? current.GetRequiredParent()
: current;
}
}
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