Aliases are Not a New Type Declaration

It's important to know that, in general, defining an Alias does not declare a "new type", instead it is just providing a shorthand for referring to some type. With an Alias definition, you are simply defining an alternative, more convenient way to refer to a type that is semantically equivalent to typing out the explicit type itself.

The example below demonstrates how variables with types declared using equivalent aliases, will in fact type-check as having the same type:

Fig 1:

alias IntList1 : [int]
alias IntList2 : [int]

var i1: IntList1 = [1];
var i2: IntList2 = [2];
var i3: [int] = [3];

i2 = i3;   # <-- IntList2 is equivalent to [int].
i1 = i2;   # <-- IntList1 is equivalent to IntList2.

print(i1);
print(i2);
print(i3);

Output:

[3]
[3]
[3]

Note on "Nominal Typing"

Nominal typing can actually be very useful for enforcing maintenance of semantic interpretations of even simple data types, and even for maintaining inter-field invariants of more complex structured data types. So, of course, Claro also provides a mechanism to define new, "nominally typed" type definitions. This will allow making a semantic distinction between two "structurally equivalent" types that have different names.

For more on this, see: User Defined Types.