`Inflight<T>` and `Preflight<T>` type modifiers

Feature Spec

Wing now includes Inflight<T> and Preflight<T> type modifiers, which allow the user to filter inflight and preflight methods from a type.

By using Inflight<T> on a type T, all preflight properties will be filtered out from T. The same happens with Preflight<T>, where all inflight properties will be filtered out from T.

It can be used as follows:

bring cloud;

// Our bucket client doesn't require any preflight access to the bucket.
class MyBucketClient {
    bucket: Inflight<cloud.Bucket>;

    init(bucket: Inflight<cloud.Bucket>) {
        // During preflight phase, `bucket` is like an empty object.
        this.bucket = bucket;
    }

    pub inflight putFile(key: str, contents: str) {
        return this.bucket.put(key, contents);
    }
}

let bucket = new cloud.Bucket();

// Since `cloud.Bucket` is a superset of `Inflight<cloud.Bucket>`, it can be automatically casted.
let client = new MyBucketClient(bucket);

Use Cases

As a developer, sometimes we want to be more explicit of the properties we need from an instance.

For example, it's useful if we're implementing a custom Bucket client that doesn't require any kind of preflight access to a bucket (which is considered elevated permissions, in a way).

Implementation Notes

No response

Component

Language Design

Community Notes

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Start with the Feature Spec and the language-design discussion; no source file or test entry point is named. Confirm the filtering and automatic-cast behavior for Inflight and Preflight, then define completion through implementation and tests covering the examples in the issue.