private static TypeSymbol GetMatchingElementType(ArrayTypeSymbol source, TypeSymbol target, ref HashSet<DiagnosticInfo> useSiteDiagnostics)
{
Debug.Assert((object)source != null);
Debug.Assert((object)target != null);
// It might be an array of same rank.
if (target.IsArray())
{
var arrayTarget = (ArrayTypeSymbol)target;
if (!arrayTarget.HasSameShapeAs(source))
{
return null;
}
return arrayTarget.ElementType;
}
// Or it might be IEnum<T> and source is rank one.
if (!source.IsSZArray)
{
return null;
}
// Arrays are specified as being convertible to IEnumerable<T>, ICollection<T> and
// IList<T>; we also honor their convertibility to IReadOnlyCollection<T> and
// IReadOnlyList<T>, and make inferences accordingly.
if (!target.IsPossibleArrayGenericInterface())
{
return null;
}
return ((NamedTypeSymbol)target).TypeArgumentWithDefinitionUseSiteDiagnostics(0, ref useSiteDiagnostics);
}
