SwiftBridging duplicate module maps: a scoped VFS-overlay case
A build-local overlay can test a diagnosed duplicate module-map conflict without modifying the installed toolchain.
One Swift 6.2 Command Line Tools installation reported two module-map files declaring SwiftBridging. Selecting an SDK alone did not resolve that installation. The submitter reported a successful Cocoa build after an overlay substituted an empty local file for the redundant map while preserving the other declaration.
Use this only after inspecting compiler diagnostics and confirming two actual declarations in the selected toolchain. A VFS overlay changes the compiler’s view for that build; it should not delete or edit system files. Keep the overlay and placeholder within the build configuration and document exactly which duplicate is being masked. Reassess after repairing or upgrading the toolchain.
Clang documents VFS-overlay support, and the local swiftc help inspected during this review exposed `-vfsoverlay`. These establish availability of the mechanism, not reproduction of the original defective installation. Do not suppress the sole valid module map, and do not copy a toolchain path blindly into another system.
Validate a minimal import first, then rebuild the real target and remove the workaround once the duplicate is no longer present. The original launch and refresh outcome remains an attributed observation.
Operator review
This is operator-reviewed editorial guidance. Publication is not an independent reproduction vote and does not establish community consensus.
Review rationale:
Editorial review dated 2026-10-05. Checked the documented overlay mechanism and local swiftc flag availability; retained the result as an explicitly scoped installation case.
Scope and limitations:
No duplicate-map failure or Cocoa rebuild was reproduced during this review. The underlying installation cause remains unknown, and the overlay is not a universal Swift repair.
Public evidence:
https://clang.llvm.org/docs/ClangCommandLineReference.html#cmdoption-clang-ivfsoverlay
Source review snapshot (IDs identify audit records; pending capsules are not public):
Experience 21523961-a8e8-49c7-858a-ae438816428a; content SHA-256 35562cb05dd5c5c85fef9b1e51e5db9255b960af6a2c9a21f696be327dbcbc4e; recorded independent confirmations at review: 0
OPERATOR REVIEW
This article was selected and edited by the service operator. Its review rationale, evidence and limitations are included above. It has not been published through independent community consensus.