Good day, swift community!
This time, I'd like to bring your attention to an everyday problem which, I'm
sure, you've all dealt with at some point.
Motivation
Many protocols have a lot of default-implemented requirements so that they can
be customized, which would otherwise be impossible to do.
For example, the Comparable protocol, which (considering its inheritance of
Equatable) states a requirement of ==, !=, <, <=, >, and >=, only requires
implementation of == and <, because all others have default implementations in
terms of these two. This forces the user to either memorize the exact set of
mandatory requirements or, in case of more complicated protocols like
Collection, constantly look up the documentation and hope that it has a section
outlining how to conform to it.
Conversely, the author of the protocol needs to manually keep track of the
requirements and their default implementations to ensure that the ones that
have to be mandatory stay mandatory and the rest of the requirements stay
default-implemented, which is also a tedious and error-prone work.
Proposed Solution
I'd like to propose the ability to mark select protocol requirements as
default, which would cause the following effects:
The compiler will emit a compile-time error if a default implementation is not
available in a non-constrained protocol extension in the same file and provide
a fix-it for inserting a template.
If a conforming type does not implement all requirements of the protocol, the
compiler will not produce fix-its for inserting a template for any default
requirements.
Example
// Equatable.swift
protocol Equatable {
static func == (_ some: Self, _ other: Self) -> Bool
default static func != (_ some: Self, _ other: Self) -> Bool
^ error: missing implementation of a default requirement `!=`; fix-it:
insert a default implementation
}
extension Equatable {
static func != (_ some: Self, _ other: Self) -> Bool {
[Your Code Here]
}
}
// Something.swift
struct Something: Equatable {
^ error: missing implementation of a non-default requirement `==`; fix-it:
insert an implementation
}
extension Something {
static func == (_ some: Something, _ other: Something) -> Bool {
[Your Code Here]
}
}
Cheers,
Gor Gyolchanyan._______________________________________________
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