How to completely bypass legacy C++ Parser validation when testing ParserASTGen

Hello everyone,

I am working on porting statement parsing logic from C++ to lib/ASTGen.

I have modified Sources/ASTGen/Stmts.swift to handle specific invalid syntax (addressing a FIXME). I am attempting to verify this change using swift-frontend. Even with the experimental feature enabled, the legacy C++ parser (lib/Parse ) seems to run a validation pass first. It rejects the invalid syntax with a standard error before my ASTGen logic is invoked.

Command: swift-frontend -parse test.swift -enable-experimental-feature ParserASTGen

Is there a specific frontend flag or build configuration that completely disables the legacy C++ parser's pre-check for top-level code? I need the driver to hand off the source text directly to the Swift parser/ASTGen pipeline without the C++ guardrails intervening.