Pattern parser throws an error when parsing patterns with explicit private attributes

[kurt-r2c]

Describe the bug
Parser engine throws up when parsing patterns with explicit private attributes, e.g.

rules:
  - id: parser-doesnt-like-private-attributes
    pattern: |
        #$ATTR(...) {
          ...
        }
    message: Semgrep found a match $ATTR
    languages: [ts,js]
    severity: WARNING

The engine parsing targets can handle private attributes just fine - this shows up if you have e.g. a rule that finds function definitions, then you use the metavariable values to construct a new Semgrep rule.

To Reproduce
https://semgrep.dev/playground/s/kx2Zz

as long as you don't use a private attribute explicitly in a pattern, the engine is happy:
https://semgrep.dev/playground/s/NbYA1

further complicating the issue, calling a private attribute with this seems to parse just fine:
https://semgrep.dev/playground/s/eqlwE

Expected behavior
this should parse.

Screenshots
If applicable, add screenshots to help explain your problem.

What is the priority of the bug to you?

• P0: blocking your adoption of Semgrep or workflow
• P1: important to fix or quite annoying
• P2: regular bug that should get fixed

Environment
semgrep.dev, semgrep 1.72.0

Use case
recursively templated scans using results from Semgrep itself