private static bool CanCastToClass(this TypeDesc thisType, TypeDesc otherType, StackOverflowProtect protect)
{
TypeDesc curType = thisType;
// If the target type has variant type parameters, we take a slower path
if (curType.HasVariance)
{
// First chase inheritance hierarchy until we hit a class that only differs in its instantiation
do
{
if (curType == otherType)
{
return true;
}
if (curType.CanCastByVarianceToInterfaceOrDelegate(otherType, protect))
{
return true;
}
curType = curType.BaseType;
}
while (curType != null);
}
else
{
// If there are no variant type parameters, just chase the hierarchy
// Allow curType to be nullable, which means this method
// will additionally return true if curType is Nullable<T> && (
// currType == otherType
// OR otherType is System.ValueType or System.Object)
// Always strip Nullable from the otherType, if present
if (otherType.IsNullable && !curType.IsNullable)
{
return thisType.CanCastTo(otherType.Instantiation[0]);
}
do
{
if (curType == otherType)
return true;
curType = curType.BaseType;
} while (curType != null);
}
return false;
}
//
// Contra/CoVariance.
//
// IEnumerable<D> can cast to IEnumerable<B> if D can cast to B and if there's no possibility that D is a value type.
//
private static bool IsGcReferenceTypeAndCastableTo(this TypeInfo fromTypeInfo, TypeInfo toTypeInfo, FoundationTypes foundationTypes)
{
if (fromTypeInfo.Equals(toTypeInfo))
return true;
if (fromTypeInfo.ProvablyAGcReferenceType(foundationTypes))
return fromTypeInfo.CanCastTo(toTypeInfo, foundationTypes);
return false;
}
//
// Contra/CoVariance.
//
// IEnumerable<D> can cast to IEnumerable<B> if D can cast to B and if there's no possibility that D is a value type.
//
private static bool IsGcReferenceTypeAndCastableTo(this Type fromTypeInfo, Type toTypeInfo)
{
if (fromTypeInfo.Equals(toTypeInfo))
return true;
if (fromTypeInfo.ProvablyAGcReferenceType())
return fromTypeInfo.CanCastTo(toTypeInfo);
return false;
}
