/// <summary>
/// Returns true if the constraint is valid. Otherwise
/// returns false and generates a diagnostic.
/// </summary>
internal static bool IsValidConstraint(
string typeParameterName,
TypeConstraintSyntax syntax,
TypeSymbolWithAnnotations type,
TypeParameterConstraintKind constraints,
ArrayBuilder <TypeSymbolWithAnnotations> constraintTypes,
DiagnosticBag diagnostics)
{
if (!IsValidConstraintType(syntax, type, diagnostics))
{
return(false);
}
// Ignore nullability when comparing constraints.
if (constraintTypes.Contains(c => type.Equals(c, TypeCompareKind.IgnoreNullableModifiersForReferenceTypes)))
{
// "Duplicate constraint '{0}' for type parameter '{1}'"
Error(diagnostics, ErrorCode.ERR_DuplicateBound, syntax, type.TypeSymbol.SetUnknownNullabilityForReferenceTypes(), typeParameterName);
return(false);
}
if (type.TypeKind == TypeKind.Class)
{
// If there is already a struct or class constraint (class constraint could be
// 'class' or explicit type), report an error and drop this class. If we don't
// drop this additional class, we may end up with conflicting class constraints.
if (constraintTypes.Count > 0)
{
// "The class type constraint '{0}' must come before any other constraints"
Error(diagnostics, ErrorCode.ERR_ClassBoundNotFirst, syntax, type.TypeSymbol);
return(false);
}
if ((constraints & (TypeParameterConstraintKind.ReferenceType)) != 0)
{
switch (type.SpecialType)
{
case SpecialType.System_Enum:
case SpecialType.System_Delegate:
case SpecialType.System_MulticastDelegate:
break;
default:
// "'{0}': cannot specify both a constraint class and the 'class' or 'struct' constraint"
Error(diagnostics, ErrorCode.ERR_RefValBoundWithClass, syntax, type.TypeSymbol);
return(false);
}
}
else if (type.SpecialType != SpecialType.System_Enum)
{
if ((constraints & TypeParameterConstraintKind.ValueType) != 0)
{
// "'{0}': cannot specify both a constraint class and the 'class' or 'struct' constraint"
Error(diagnostics, ErrorCode.ERR_RefValBoundWithClass, syntax, type.TypeSymbol);
return(false);
}
else if ((constraints & TypeParameterConstraintKind.Unmanaged) != 0)
{
// "'{0}': cannot specify both a constraint class and the 'unmanaged' constraint"
Error(diagnostics, ErrorCode.ERR_UnmanagedBoundWithClass, syntax, type.TypeSymbol);
return(false);
}
}
}
return(true);
}
