// https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/keywords/default-values-table
/// <summary>
/// Creates a new <see cref="ExpressionSyntax"/> that represents default value of the specified type symbol.
/// </summary>
/// <param name="typeSymbol"></param>
/// <param name="options"></param>
/// <param name="type"></param>
/// <param name="format"></param>
public static ExpressionSyntax GetDefaultValueSyntax(
this ITypeSymbol typeSymbol,
DefaultSyntaxOptions options = DefaultSyntaxOptions.None,
TypeSyntax type = null,
SymbolDisplayFormat format = null)
{
if (typeSymbol == null)
{
throw new ArgumentNullException(nameof(typeSymbol));
}
if ((options & DefaultSyntaxOptions.UseDefault) != 0)
{
return(CreateDefault());
}
if (typeSymbol.IsReferenceType ||
typeSymbol.TypeKind == TypeKind.Pointer ||
typeSymbol.IsNullableType())
{
return(NullLiteralExpression());
}
if (typeSymbol.TypeKind == TypeKind.Enum)
{
IFieldSymbol fieldSymbol = CSharpUtility.FindEnumDefaultField((INamedTypeSymbol)typeSymbol);
if (fieldSymbol != null)
{
return(SimpleMemberAccessExpression(GetTypeSyntax(), IdentifierName(fieldSymbol.Name)));
}
return(CastExpression(GetTypeSyntax(), NumericLiteralExpression(0)).WithSimplifierAnnotation());
}
switch (typeSymbol.SpecialType)
{
case SpecialType.System_Boolean:
return(FalseLiteralExpression());
case SpecialType.System_Char:
return(CharacterLiteralExpression('\0'));
case SpecialType.System_SByte:
case SpecialType.System_Byte:
case SpecialType.System_Int16:
case SpecialType.System_UInt16:
case SpecialType.System_Int32:
case SpecialType.System_UInt32:
case SpecialType.System_Int64:
case SpecialType.System_UInt64:
case SpecialType.System_Decimal:
case SpecialType.System_Single:
case SpecialType.System_Double:
return(NumericLiteralExpression(0));
}
return(CreateDefault());
TypeSyntax GetTypeSyntax()
{
return(type ?? typeSymbol.ToTypeSyntax(format).WithSimplifierAnnotation());
}
ExpressionSyntax CreateDefault()
{
if ((options & DefaultSyntaxOptions.AllowDefaultLiteral) != 0)
{
return(DefaultLiteralExpression());
}
return(DefaultExpression(GetTypeSyntax()));
}
}
public static Task <Document> ToMultiLineAsync(
Document document,
ExpressionSyntax expression,
SemanticModel semanticModel,
CancellationToken cancellationToken = default(CancellationToken))
{
SyntaxTrivia trivia = expression.GetIndentation(cancellationToken);
string indentation = Environment.NewLine + trivia.ToString() + SingleIndentation(trivia).ToString();
TextChange? textChange = null;
List <TextChange> textChanges = null;
foreach (SyntaxNode node in CSharpUtility.EnumerateExpressionChain(expression))
{
switch (node.Kind())
{
case SyntaxKind.SimpleMemberAccessExpression:
{
var memberAccess = (MemberAccessExpressionSyntax)node;
if (memberAccess.Expression.IsKind(SyntaxKind.ThisExpression))
{
break;
}
if (semanticModel
.GetSymbol(memberAccess.Expression, cancellationToken)?
.Kind == SymbolKind.Namespace)
{
break;
}
AddTextChange(memberAccess.OperatorToken);
break;
}
case SyntaxKind.MemberBindingExpression:
{
var memberBinding = (MemberBindingExpressionSyntax)node;
AddTextChange(memberBinding.OperatorToken);
break;
}
}
}
if (textChanges != null)
{
TextChange[] arr = textChanges.ToArray();
Array.Reverse(arr);
return(document.WithTextChangesAsync(arr, cancellationToken));
}
else
{
return(document.WithTextChangeAsync(textChange.Value, cancellationToken));
}
void AddTextChange(SyntaxToken operatorToken)
{
var tc = new TextChange(new TextSpan(operatorToken.SpanStart, 0), indentation);
if (textChange == null)
{
textChange = tc;
}
else
{
(textChanges ?? (textChanges = new List <TextChange>()
{
textChange.Value
})).Add(tc);
}
}
}