private static TypeSymbol GetNextDeclaredBase(NamedTypeSymbol type, ConsList <TypeSymbol> basesBeingResolved, CSharpCompilation compilation, ref PooledHashSet <NamedTypeSymbol> visited)
{
// We shouldn't have visited this type earlier.
Debug.Assert(visited == null || !visited.Contains(type.OriginalDefinition));
if (basesBeingResolved != null && basesBeingResolved.ContainsReference(type.OriginalDefinition))
{
return(null);
}
if (type.SpecialType == SpecialType.System_Object)
{
type.SetKnownToHaveNoDeclaredBaseCycles();
return(null);
}
var nextType = type.GetDeclaredBaseType(basesBeingResolved);
// types with no declared bases inherit object's members
if ((object)nextType == null)
{
SetKnownToHaveNoDeclaredBaseCycles(ref visited);
return(GetDefaultBaseOrNull(type, compilation));
}
var origType = type.OriginalDefinition;
if (nextType.KnownToHaveNoDeclaredBaseCycles)
{
origType.SetKnownToHaveNoDeclaredBaseCycles();
SetKnownToHaveNoDeclaredBaseCycles(ref visited);
}
else
{
// start cycle tracking
visited = visited ?? PooledHashSet <NamedTypeSymbol> .GetInstance();
visited.Add(origType);
if (visited.Contains(nextType.OriginalDefinition))
{
return(GetDefaultBaseOrNull(type, compilation));
}
}
return(nextType);
}