"design:paramnames" metadata key

From https://github.com/Microsoft/TypeScript/pull/2589

A few notes on metadata:

• Type metadata uses the metadata key “design:type”.
• Parameter type metadata uses the metadata key “design:paramtypes”.
• Return type metadata uses the metadata key “design:returntype”.

Can you please add support for a "design:paramnames" metadata key? It would return the design-time names of the arguments of a function

I can convert a function to string at runtime using Function.prototype.toString() and then use a couple of Regex to get the parameter names:

STRIP_COMMENTS = /((\/\/.*$)|(\/\*[\s\S]*?\*\/))/mg;
ARGUMENT_NAMES = /([^\s,]+)/g;

But when a minifier/compressor is used the param names become "a", "b" …

I would like to have a way to access the design-time names of the arguments of a function at run-time even after compression.

[raymondfeng]

+1. At LoopBack, we introduce decorators to annotate method parameters to describe how to map methods to REST APIs. It will be great that we can infer parameter types/names from the design time metadata. For example:

@returnValue()
async createOrder(@param() order: Order): Promise<Order> {
  // ...
}

We would like to know:
- The parameter name ('order') N/A today
- The parameter type (Order) (It's already supported, but not for array item types)
- The return type (Promise) but we care more about `Promise<Order>`

[nodkz]

Duplicate https://github.com/Microsoft/TypeScript/issues/12626