Xcode 13 indexing regression for Swift static libraries

Summary:

Currently if you have a project that links a pre-compiled Swift static library (with or without .xcframework), when you try and jump to definition, Xcode fails and shows the question mark pop-up. Syntax highlighting also doesn't work for symbols from the pre-compiled library.

It's a regression from Xcode 13 because everything works as expected in Xcode 12.5.

Steps to Reproduce:

1. Pre-compile a Swift static library in a project
2. Create a new project, copy the pre-compiled library into the root of the new project
3. Add the library path to SWIFT_INCLUDE_PATHS and LIBRARY_SEARCH_PATHS
4. Reference a symbol from the library
5. Build (this should be successful)
6. Jump to definition on either the import declaration or the symbol. Also check syntax highlighting

Expected Results:

You see the generated interface of the Swift module and syntax highlighting

Actual Results:

Xcode shows the question mark modal and syntax highlighting doesn't work

Version:

Xcode 13.0 (13A233) Xcode 13.1 RC (13A1030d)

Tested with macOS Big Sur 11.6 and Intel MacBook Pro.

Sample projects:

There are 3 sample projects in this repository:

• One to build the Swift static library (named StaticAnimals);

• One iOS app integrating the static library as .xcframework;

• One iOS app integrating the static library .a directly, without .xcframework.

• Run make setup to build de Swift static library (StaticAnimals) for iOS Simulator.

• Open XCFrameworkRegressionProject/XCFrameworkRegression.xcodeproj with Xcode 13

• Go to Here.swift

• Build for simulator (should be succesful)

• Check syntax highlighting and jump to definition

• Open SwiftStaticRegressionProject/SwiftStaticRegression.xcodeproj with Xcode 13

• Go to Here.swift

• Build for simulator (should be succesful)

• Check syntax highlighting and jump to definition

• Note: for this project, only .swiftmodule and .swiftdoc was provided, because AFAIK .swiftinterface and .swiftsourceinfo are optional

Both projects can also be tested with Xcode 12.5 for comparison.