Aliases

Unlike named types, which create a completely new type with an underlying base type, aliases are simply a new name for an existing type.

Aliases do not create a distinct type.

You define an alias using the type keyword with =:

type Age = int

here, Age is exactly equivalent to int.

so because Age is just another name for int, they are fully interchangeable:

type Age = int

egg a Age = 5
egg y int = a
putln(y)

output: 5

no conversion is required because Age and int are the same type.

alias vs named Type

Compare:

type Age int

this creates a new type based on int.

Now this would require explicit conversion:

egg a Age = 5
egg y int = int(a)  // required

but with an alias:

type Age = int

egg a Age - 5
egg y int = a

no conversion is needed.