Naming - core

[happy-barney]

Proposal introduces with two new names into perl's need-to-know-knowledge-base

• check
• of
• returns

These names should be used in any discussion / example.

New names should come here and only here (to not distract focus in another discussions).

[happy-barney]

I'd like to suggest different name - contract, coming from data contract term often used in books and papers.

Pros:

• it's nice buzzword, once available, discussions about Perl will sound professional
• contract can be bidirectional - not only data related but also declaring, eg when comparing with Java:class Foo :contract (some interface & another interface)
• contract will can replace all three check, of, and returns
• contract can describe not only internal contracts (vars, subs, domains), but also external contracts (ie, generate schema from Perl's contracts)

Cons:

• concept of data contracts is little bit more abstract

Examples

declare custom contract

contract Foo => as Str[ min_length => 3, max_length => 16, pattern => qr/.../ ];

declare variable contract

my $foo :contract (Foo) = ...;

declare sub contract (aka returns)

sub Foo :contact (Foo) { ... }

Class / package contract

contract Foo => Can [ method ] & Can [ another_method :contract (Int -> Int, Int) ];

class Bar :contact (Foo);
package Bar: contract (Foo);

Import contracts:

use Foo :contract (Foo_Bar, Foo_Baz) qw (param1 param2);

Export contracts:
Contract is exported by default except of contracts declared as local:

contract Exported ...;
local contract Not_Exported ...;