Multi-lined signatures collapsing

[n-gist]

Hi. I'm trying to achieve folding to one line if function signature is splitted to multiple lines:

  "[typescript]": {
    "explicitFolding.rules": [
      {
        "begin": "{",
        "end": "}"
      },
      {
        "begin": "[",
        "end": "]"
      },
      {
        "begin": "(",
        "end": ")"
      }
    ]
  }

The case:

const compareDiagnostics = (
	entry1: [vscode.Uri, vscode.Diagnostic[]],
	entry2: [vscode.Uri, vscode.Diagnostic[]]
) => {
	if (entry1[0].path < entry2[0].path) return -1
	if (entry1[0].path > entry2[0].path) return 1
	return 0
}

Currently, only function header folds, and body is not foldable.

The best what I managed to achieve, is to add 4th setting:

  "[typescript]": {
    "explicitFolding.rules": [
      {
        "begin": "{",
        "end": "}"
      },
      {
        "begin": "[",
        "end": "]"
      },
      {
        "begin": "(",
        "end": ")"
      },
      {
        "beginRegex": "^.*\\($",
        "end": "}"
      }
    ]
  },

It seems, that 4th rule somehow matches, but doesn't works, and this way it excludes this case from processing by extension. This enables default VS Code folding here, which folds it to 2 lines (keeps trailing } on second line)

Is it possible to fold this case to one line in current version?

I have also tried some regular expressions, something like the (should be placed as first rule):

      {
        "beginRegex": "^.*\\($",
        "middleRegex": "^\\) => \\{$",
        "endRegex": "^\\}$"
      }

This makes it foldable to two lines, but then the other, one-lined-signature cases stops working