Unaccountable type deduction change when building via CMake/Xcode

[dabrahams]

Description

With the Swift ArgumentParser project:

cmake -D BUILD_EXAMPLES=NO -D BUILD_TESTING=NO -G Ninja -S . -B .ninja-build &&  cmake --build .ninja-build

works fine, but

cmake -D BUILD_EXAMPLES=NO -D BUILD_TESTING=NO -G Xcode -S . -B .xcode-build &&  cmake --build .xcode-build

fails with:

/Users/dave/src/swift-project/swift-argument-parser/Sources/ArgumentParser/Parsing/CommandParser.swift:289:101: error: value of optional type 'GenerateCompletions?' must be unwrapped to refer to member 'generateCompletionScript' of wrapped base type 'GenerateCompletions'
      throw CommandError(commandStack: commandStack, parserError: .completionScriptRequested(shell: result.generateCompletionScript))
                                                                                                    ^
/Users/dave/src/swift-project/swift-argument-parser/Sources/ArgumentParser/Parsing/CommandParser.swift:289:101: note: chain the optional using '?' to access member 'generateCompletionScript' only for non-'nil' base values
      throw CommandError(commandStack: commandStack, parserError: .completionScriptRequested(shell: result.generateCompletionScript))
                                                                                                    ^
                                                                                                          ?
/Users/dave/src/swift-project/swift-argument-parser/Sources/ArgumentParser/Parsing/CommandParser.swift:295:8: error: value of optional type 'AutodetectedGenerateCompletions?' must be unwrapped to refer to member 'generateCompletionScript' of wrapped base type 'AutodetectedGenerateCompletions'
       result.generateCompletionScript
       ^
/Users/dave/src/swift-project/swift-argument-parser/Sources/ArgumentParser/Parsing/CommandParser.swift:295:8: note: chain the optional using '?' to access member 'generateCompletionScript' only for non-'nil' base values
       result.generateCompletionScript
       ^
             ?
/Users/dave/src/swift-project/swift-argument-parser/Sources/ArgumentParser/Parsing/CommandParser.swift:295:8: note: force-unwrap using '!' to abort execution if the optional value contains 'nil'
       result.generateCompletionScript
       ^
             !

The types are actually deduced differently. You can see the different types if you open the generated Xcode project and the SPM project with Xcode.

Reproduction

See above.

Expected behavior

The xcode build works; the types are deduced the same.

Environment

swift-driver version: 1.87.3 Apple Swift version 5.9.2 (swiftlang-5.9.2.2.56 clang-1500.1.0.2.5)
Target: arm64-apple-macosx14.0

Additional information

No response

[finagolfin]

Can you reproduce with 5.10?

[dabrahams]

Yes; log attached