TypeScript 5's decorators are not supported

[jwbth]

The example from the docs:

import {memoizeDecorator} from 'memoize';

class Example {
	index = 0

	@memoizeDecorator()
	counter() {
		return ++this.index;
	}
}

returns the following error in TypeScript 5:

Unable to resolve signature of method decorator when called as an expression.
  The runtime will invoke the decorator with 2 arguments, but the decorator expects 3. ts(1241)
index.d.ts(109, 183): An argument for 'descriptor' was not provided.

The cause of this issue, I assume, is that the library only supports the stage 2 implementation of decorators. TypeScript 5 supports stage 3 decorator implementation without --experimentalDecorators, see https://devblogs.microsoft.com/typescript/announcing-typescript-5-0/#decorators.

[fregante]

If we were to support both, testing them would be an issue:

• either run a second test file with --experimentalDecorators enabled
• or "manually polyfill" the previous version in the class constructor, rather than calling it as an actual decorator

Dropping support for the old one might be troublesome for people who are using --emitDecoratorMetadata, but I think it's not the end of the world, they can stay on memoize@10. I propose just dropping support.

The blog post shows how to type these decorators: https://devblogs.microsoft.com/typescript/announcing-typescript-5-0/#writing-well-typed-decorators