Before You File a Proposal Please Confirm You Have Done The Following...

• I have searched for related issues and found none that match my proposal.
• I have searched the current rule list and found no rules that match my proposal.
• I have read the FAQ and my problem is not listed.

Relevant Package

ast-spec

My proposal is suitable for this project

• I believe my proposal would be useful to the broader TypeScript community (meaning it is not a niche proposal).

Description

class Test1 {
  constructor(
    private [foo] = [1],
    private { bar } = { bar: 1 },
    private ...baz
  ) { }
}

Currently these three parameter properties are semantic errors in TS and are similarly allowed by our parser.
However they are all non-sensical. The first two don't even transpile to generate a property!

We should make these hard errors to block the syntax so that we can refine our TSParameterProperty.parameter type to exclude the invalid states.

An additional case which is already a hard TS parser error that we should pre-narrow the types for -- the .left of an assignment parameter property must always be an Identifier.