Artem Chikin 7be7ab1e2b [Dependency Scanning][C++Interop] Do not query 'CxxStdlib' Swift overlay for textual modules which were not built with c++interop ...

When we discover a textual module dependency which is a module which was not originally built from source using C++ interop (specifying '-formal-cxx-interoperability-mode=off'), avoid looking up the C++ standard library Swift overlay for it. This is required for the case of the 'Darwin' module, for example, which includes headers which map to C++ stdlib headers when the compiler is operating in C++ interop mode, but the C++ standard library Swift overlay module itself depends on 'Darwin', which results in a cycle. To resolve such situations, we can rely on the fact that Swift textual interfaces of modules which were not built with C++ interop must be able to build without importing the C++ standard library Swift overlay, so we avoid specifying it as a dependency for such modules.

The primary source module, as well as Swift textual module dependencies which *were* built with C++ interop will continue getting a direct depedency of the 'CxxStdlib' Swift module.

Resolves rdar://150222155

2025-05-09 13:00:59 -07:00

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