Composite type comparison

[jules]

Does this help?

Why [1, 2, 3] is not a Vector{Number}?

Just to extract some relevant points because the manual is quite dense: Vector{Number} is a concrete type, and [1, 2, 3] has type Vector{Int}, which is also a concrete type. One concrete type is never a subtype of another concrete type, they are the leaves of the type tree. Vector{Number} is concrete, even though Number is not a concrete type. That’s because it has a concrete implementation which can store all types that are subtypes of Number, it has a specific memory layout etc. On the other…

In addition, the Tuple type is the only type which is covariant, which means that a Tuple is subtype of another Tuple if each of its element types is a subtype of the corresponding element type in the supertype Tuple.