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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.Collections.Immutable;
using System.Linq;
using System.Threading;
using Microsoft.CodeAnalysis.Classification;
using Microsoft.CodeAnalysis.Classification.Classifiers;
using Microsoft.CodeAnalysis.Collections;
using Microsoft.CodeAnalysis.CSharp.Extensions;
using Microsoft.CodeAnalysis.CSharp.Syntax;
using Microsoft.CodeAnalysis.Shared.Extensions;
using Microsoft.CodeAnalysis.Text;
using Roslyn.Utilities;
namespace Microsoft.CodeAnalysis.CSharp.Classification.Classifiers;
internal class SyntaxTokenClassifier : AbstractSyntaxClassifier
{
public override ImmutableArray<int> SyntaxTokenKinds { get; } = [(int)SyntaxKind.LessThanToken];
private static readonly Func<ITypeSymbol, bool> s_shouldInclude = t => t.TypeKind != TypeKind.Error && t.GetArity() > 0;
public override void AddClassifications(
SyntaxToken lessThanToken,
TextSpan textSpan,
SemanticModel semanticModel,
ClassificationOptions options,
SegmentedList<ClassifiedSpan> result,
CancellationToken cancellationToken)
{
var syntaxTree = semanticModel.SyntaxTree;
if (syntaxTree.IsInPartiallyWrittenGeneric(lessThanToken.Span.End, cancellationToken, out var identifier))
{
// IsInPartiallyWrittenGeneric will return true for things that could be
// partially generic method calls (as opposed to partially written types).
//
// For example: X?.Y<
//
// In this case, this could never be a type, and we do not want to try to
// resolve it as such as it can lead to inappropriate classifications.
if (CouldBeGenericType(identifier))
{
var types = semanticModel.LookupTypeRegardlessOfArity(identifier, cancellationToken);
if (types.Any(s_shouldInclude))
{
#nullable disable // Can 'GetClassificationForType(types.First()' be null here?
result.Add(new ClassifiedSpan(identifier.Span, GetClassificationForType(types.First())));
#nullable enable
}
}
}
}
private static bool CouldBeGenericType(SyntaxToken identifier)
{
// Look for patterns that indicate that this could never be a partially written
// generic *Type* (although it could be a partially written generic method).
if (identifier.Parent is not IdentifierNameSyntax identifierName)
{
// Definitely not a generic type if this isn't even an identifier name.
return false;
}
if (identifierName.IsParentKind(SyntaxKind.MemberBindingExpression))
{
// anything?.Identifier is never a generic type.
return false;
}
// ?.X.Identifier or ?.X.Y.Identifier is never a generic type.
if (identifierName.IsSimpleMemberAccessExpressionName() ||
identifierName.IsMemberBindingExpressionName())
{
if (identifier.Parent.IsParentKind(SyntaxKind.ConditionalAccessExpression))
return false;
}
// Add more cases as necessary.
return true;
}
}
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