Structures combine other data structures together. They are declared with the
data keyword followed by the structure identifier and body. The trailing list separator is recommended but optional.
data Structure:field: Type,
If the body is on the same line, it will be terminated by a line break instead of a block close.
data Structure: field: Type
Structures can have template type parameters. Template identifiers are preceded with the template token.
data Structure<$Type>:field: $Type,