patterns: Constructing a pattern should also create a static type

[gibson042]

What is the Problem Being Solved?

Independently constructing runtime patterns with M matcher methods and defining static types with @typedef is cumbersome and error-prone, leading us to implement manual validation even when M would be useful (cf. Agoric/agoric-sdk#9169 (comment)). It should instead be possible to extract static types from patterns, e.g.

import { mustMatch } from '@endo/patterns';

const BundleShape = M.or(…);

/**
 * @param {TypeFromPattern<typeof BundleShape>} bundle
 */
const evaluateBundle = bundle => {
  mustMatch(bundle, BundleShape);
  const { moduleFormat } = bundle;
  …
};

evaluateBundle({}); // static error

Description of the Design

Annotate Matcher functions to return annotated values, and define a utility type for reading such annotations into types.

Security Considerations

None AFAIK

Scaling Considerations

None AFAIK

Test Plan

We should take examples from existing endo and agoric-sdk code.

Compatibility Considerations

None AFAIK

Upgrade Considerations

Nothing out of the ordinary, just the usual caveat that functionality is not incorporated into mainnet vats until they are upgraded.

[gibson042]

A successful experiment that leverages const annotation for raw primitives: TypeScript Playground

I'm near the current limits of my knowledge, but this looks very promising as a step beyond even https://github.com/Agoric/agoric-sdk/blob/master/packages/internal/src/types.d.ts#L75-L96 .

[gibson042]

And a version with recursive types (which must be actual TypeScript AFAIK) for recognizing e.g. { version: /** @type {const} */ (1), contents: M.string() } as a Pattern without the need for a wrapping call: TypeScript Playground