Conversion ImplicitEnumerationConversion(ResolveResult rr, IType toType)
{
// C# 4.0 spec: §6.1.3
Debug.Assert(rr.IsCompileTimeConstant);
TypeCode constantType = ReflectionHelper.GetTypeCode(rr.Type);
if (constantType >= TypeCode.SByte && constantType <= TypeCode.Decimal && Convert.ToDouble(rr.ConstantValue) == 0)
{
if (NullableType.GetUnderlyingType(toType).Kind == TypeKind.Enum)
{
return(Conversion.EnumerationConversion(true, NullableType.IsNullable(toType)));
}
}
return(Conversion.None);
}
Conversion ExplicitNullableConversion(IType fromType, IType toType)
{
// C# 4.0 spec: §6.1.4
if (NullableType.IsNullable(toType) || NullableType.IsNullable(fromType))
{
IType t = NullableType.GetUnderlyingType(toType);
IType s = NullableType.GetUnderlyingType(fromType);
if (IdentityConversion(s, t))
{
return(Conversion.ExplicitNullableConversion);
}
if (AnyNumericConversion(s, t))
{
return(Conversion.ExplicitLiftedNumericConversion);
}
if (ExplicitEnumerationConversion(s, t))
{
return(Conversion.EnumerationConversion(false, true));
}
}
return(Conversion.None);
}
Conversion ExplicitConversionImpl(IType fromType, IType toType)
{
// This method is called after we already checked for implicit conversions,
// so any remaining conversions must be explicit.
if (AnyNumericConversion(fromType, toType))
{
return(Conversion.ExplicitNumericConversion);
}
if (ExplicitEnumerationConversion(fromType, toType))
{
return(Conversion.EnumerationConversion(false, false));
}
Conversion c = ExplicitNullableConversion(fromType, toType);
if (c.IsValid)
{
return(c);
}
if (ExplicitReferenceConversion(fromType, toType))
{
return(Conversion.ExplicitReferenceConversion);
}
if (UnboxingConversion(fromType, toType))
{
return(Conversion.UnboxingConversion);
}
if (ExplicitTypeParameterConversion(fromType, toType))
{
// Explicit type parameter conversions that aren't also
// reference conversions are considered to be unboxing conversions
return(Conversion.UnboxingConversion);
}
if (ExplicitPointerConversion(fromType, toType))
{
return(Conversion.ExplicitPointerConversion);
}
return(UserDefinedExplicitConversion(fromType, toType));
}