// https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/keywords/default-values-table
private static ExpressionSyntax GetDefaultValueSyntaxImpl(ITypeSymbol typeSymbol, TypeSyntax type, SemanticModel semanticModel, int position, SymbolDisplayFormat format = null)
{
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));
}
if (typeSymbol.IsNullableType())
{
return(NullLiteralExpression());
}
if (typeSymbol.BaseType?.SpecialType == SpecialType.System_Enum)
{
IFieldSymbol fieldSymbol = typeSymbol.FindFieldWithConstantValue(0);
if (fieldSymbol != null)
{
type = type ?? (typeSymbol.ToMinimalTypeSyntax(semanticModel, position, format));
Debug.Assert(type != null);
return(SimpleMemberAccessExpression(type, IdentifierName(fieldSymbol.Name)));
}
else
{
return(NumericLiteralExpression(0));
}
}
if (typeSymbol.IsReferenceType)
{
return(NullLiteralExpression());
}
type = type ?? (typeSymbol.ToMinimalTypeSyntax(semanticModel, position, format));
Debug.Assert(type != null);
return(DefaultExpression(type));
}
internal static ExpressionSyntax GetDefaultValueMinimalSyntax(this IParameterSymbol parameterSymbol, SemanticModel semanticModel, int position, SymbolDisplayFormat format = null)
{
if (parameterSymbol == null)
{
throw new ArgumentNullException(nameof(parameterSymbol));
}
if (!parameterSymbol.HasExplicitDefaultValue)
{
throw new ArgumentException("Parameter does not specify default value.", nameof(parameterSymbol));
}
object value = parameterSymbol.ExplicitDefaultValue;
ITypeSymbol typeSymbol = parameterSymbol.Type;
if (typeSymbol.TypeKind == TypeKind.Enum)
{
if (value == null)
{
return(NullLiteralExpression());
}
IFieldSymbol fieldSymbol = typeSymbol.FindFieldWithConstantValue(value);
TypeSyntax type = typeSymbol.ToMinimalTypeSyntax(semanticModel, position, format);
if (fieldSymbol != null)
{
return(SimpleMemberAccessExpression(type, IdentifierName(fieldSymbol.Name)));
}
else
{
return(CastExpression(type, LiteralExpression(value)));
}
}
if (value == null &&
!typeSymbol.IsReferenceTypeOrNullableType())
{
return(DefaultExpression(typeSymbol.ToMinimalTypeSyntax(semanticModel, position, format)));
}
return(LiteralExpression(value));
}
private static ExpressionSyntax ToDefaultExpression(ITypeSymbol typeSymbol, TypeSyntax type, SemanticModel semanticModel, int position, SymbolDisplayFormat format = null)
{
if (typeSymbol.IsErrorType())
{
return(null);
}
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(ZeroLiteralExpression());
}
if (typeSymbol.IsConstructedFrom(SpecialType.System_Nullable_T))
{
return(NullLiteralExpression());
}
if (typeSymbol.BaseType?.SpecialType == SpecialType.System_Enum)
{
IFieldSymbol fieldSymbol = typeSymbol.FindFieldWithConstantValue(0);
if (fieldSymbol != null)
{
if (type == null)
{
type = (semanticModel != null)
? typeSymbol.ToMinimalTypeSyntax(semanticModel, position, format)
: typeSymbol.ToTypeSyntax().WithSimplifierAnnotation();
}
Debug.Assert(type != null);
return(SimpleMemberAccessExpression(type, IdentifierName(fieldSymbol.Name)));
}
else
{
return(ZeroLiteralExpression());
}
}
if (typeSymbol.IsReferenceType)
{
return(NullLiteralExpression());
}
if (type == null)
{
type = (semanticModel != null)
? typeSymbol.ToMinimalTypeSyntax(semanticModel, position, format)
: typeSymbol.ToTypeSyntax().WithSimplifierAnnotation();
}
Debug.Assert(type != null);
return(DefaultExpression(type));
}