DependenciesScanner: teach the scanner to handle cross-import overlays

[nkcsgexi]

Swift cross-import overlays are implicitly imported. The dependencies scanner needs to read the YAML files to figure out these modules and add them to the dependencies graph.

[nkcsgexi]

@swift-ci please smoke test

[nkcsgexi]

@swift-ci please smoke test

[DougGregor]

I think we should report the YAML files we loaded as dependencies, right?

[nkcsgexi]

Good catch! Does it suffice if we add the YAML file as part of the sources of this depending module?

[davezarzycki]

This is failing to build with master-next for me. Do you might if I switch to emplace_back which does work?

/home/dave/ro_s/n/swift/lib/FrontendTool/ScanDependencies.cpp:167:20: error: no matching member function for call to 'push_back'
            result.push_back({overlayName.str(), found->getKind()});
            ~~~~~~~^~~~~~~~~
/p/llvm/bin/../include/c++/v1/vector:713:36: note: candidate function not viable: cannot convert initializer list argument to 'const std::__1::__vector_base<std::__1::pair<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>, swift::ModuleDependenciesKind>, std::__1::allocator<std::__1::pair<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>, swift::ModuleDependenciesKind>>>::value_type' (aka 'const std::__1::pair<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>, swift::ModuleDependenciesKind>')
    _LIBCPP_INLINE_VISIBILITY void push_back(const_reference __x);
                                   ^
/p/llvm/bin/../include/c++/v1/vector:716:36: note: candidate function not viable: cannot convert initializer list argument to 'std::__1::vector<std::__1::pair<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>, swift::ModuleDependenciesKind>, std::__1::allocator<std::__1::pair<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>, swift::ModuleDependenciesKind>>>::value_type' (aka 'std::__1::pair<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>, swift::ModuleDependenciesKind>')
    _LIBCPP_INLINE_VISIBILITY void push_back(value_type&& __x);
                                   ^
1 error generated.

[nkcsgexi]

@davezarzycki ah, thanks for letting me know! Feel free to change this to emplace_back.