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Named Generic Type Parameter #26834
Description
Search Terms
Suggestion
Allow generic consumer to pass generic argument by name, for instance:
interface Provider<Foo, Bar, Baz, Qux, Quux, ...> {
foo: Foo
bar: Bar
tup: [Baz, Qux, Quux]
...
}
type Consumer = Provider<
Foo = number,
Bar = string,
...
>
let consumer: Provider<
Foo = {},
Bar = [],
...
>This would allow us to write and use a generic with thousands of parameter without decreasing readability.
NOTES
- Before you ask, this feature request is not a duplicate of Proposal: allow type arguments of generic being named #22631 in any shape or form.
- This is similar to keyword (named) arguments in Python.
- Vanilla JavaScript doesn't need keyword arguments as it already has objects, but there's no equivalent for TypeScript generic arguments.
Use Cases
Above
Examples
Above
Checklist
My suggestion meets these guidelines:
- This wouldn't be a breaking change in existing TypeScript / JavaScript code
- This wouldn't change the runtime behavior of existing JavaScript code
- This could be implemented without emitting different JS based on the types of the expressions
- This isn't a runtime feature (e.g. new expression-level syntax)
Activity
svieira commentedon Sep 1, 2018
Take a look at #23696 where this was tried. There was some concern that this made formerly private interfaces (the names of generic types) public. Because of this concern the PR was superseded by #26349
RyanCavanaugh commentedon Sep 17, 2018
We're still investigating the whole named type arguments story as part of partial inference and handling of generics defaults (see linked PRs as suggested).
I think we can confidently say that the "simple" case of passing type arguments by name has been mostly ruled out due to compat concerns - we have been very careful so far to make type parameter names not observable outside the declaration itself and would prefer to keep it that way unless there's absolutely no other way to accomplish the task.
typescript-bot commentedon Dec 14, 2018
This issue has been marked as a 'Duplicate' and has seen no recent activity. It has been automatically closed for house-keeping purposes.