public Builder(TypeSystem typeSystem)
{
// Don't store the typeSystem in this; we may not access it outside of Flush().
this.NullableNode = typeSystem.NullableNode;
this.NonNullNode = typeSystem.NonNullNode;
this.ObliviousNode = typeSystem.ObliviousNode;
this.VoidType = typeSystem.VoidType;
}
/// <summary>
/// Gets a nullability node that is nullable iff either input is nullable.
/// </summary>
public NullabilityNode Join(NullabilityNode a, NullabilityNode b, EdgeLabel edgeLabel)
{
if (a == b)
{
return(a);
}
if (a.NullType == NullType.NonNull)
{
return(b);
}
if (b.NullType == NullType.NonNull)
{
return(a);
}
if (a.NullType == NullType.Oblivious)
{
return(b);
}
if (b.NullType == NullType.Oblivious)
{
return(a);
}
if (a.NullType == NullType.Nullable)
{
return(a);
}
if (b.NullType == NullType.Nullable)
{
return(b);
}
var newNode = CreateHelperNode();
CreateEdge(a, newNode, edgeLabel);
CreateEdge(b, newNode, edgeLabel);
return(newNode);
}
/// <summary>
/// Creates an edge source->target.
/// </summary>
public NullabilityEdge?CreateEdge(NullabilityNode source, NullabilityNode target)
{
// Ignore a bunch of special cases where the edge won't have any effect on the overall result:
source = source.ReplacedWith;
target = target.ReplacedWith;
if (source == target)
{
return(null);
}
if (source.NullType == NullType.NonNull || source.NullType == NullType.Oblivious)
{
return(null);
}
if (target.NullType == NullType.Nullable || target.NullType == NullType.Oblivious)
{
return(null);
}
var edge = new NullabilityEdge(source, target);
Debug.WriteLine($"New edge: {source.Name} -> {target.Name}");
newEdges.Add(edge);
return(edge);
}