0.61.5 -> 0.62.2 - Build error with watchOS

Environment

System:
    OS: macOS 10.15.4
    CPU: (16) x64 Intel(R) Core(TM) i9-9880H CPU @ 2.30GHz
    Memory: 2.02 GB / 32.00 GB
    Shell: 5.7.1 - /bin/zsh
  Binaries:
    Node: 12.7.0 - /usr/local/bin/node
    Yarn: 1.22.4 - /usr/local/bin/yarn
    npm: 6.14.4 - /usr/local/bin/npm
    Watchman: 4.9.0 - /usr/local/bin/watchman
  SDKs:
    iOS SDK:
      Platforms: iOS 13.4, DriverKit 19.0, macOS 10.15, tvOS 13.4, watchOS 6.2
  IDEs:
    Xcode: 11.4.1/11E503a - /usr/bin/xcodebuild
  npmPackages:
    react: 16.11.0 => 16.11.0
    react-native: 0.62.2 => 0.62.2
  npmGlobalPackages:
    react-native-create-library: 3.1.2

Upgrading version

0.61.5 -> 0.62.2

Description

Error building watchOS app after upgrading from React Native 61.5:

Undefined symbols for architecture i386:
  "_swift_getOpaqueTypeConformance", referenced from:
      associated type witness table accessor for SwiftUI.View.Body : SwiftUI.View in AwesomeProject_Watch_Extension.ContentView : SwiftUI.View in AwesomeProject_Watch_Extension in ContentView.o
      associated type witness table accessor for SwiftUI.PreviewProvider.Previews : SwiftUI.View in AwesomeProject_Watch_Extension.ContentView_Previews : SwiftUI.PreviewProvider in AwesomeProject_Watch_Extension in ContentView.o
      associated type witness table accessor for SwiftUI.View.Body : SwiftUI.View in AwesomeProject_Watch_Extension.NotificationView : SwiftUI.View in AwesomeProject_Watch_Extension in NotificationView.o
      associated type witness table accessor for SwiftUI.PreviewProvider.Previews : SwiftUI.View in AwesomeProject_Watch_Extension.NotificationView_Previews : SwiftUI.PreviewProvider in AwesomeProject_Watch_Extension in NotificationView.o
ld: symbol(s) not found for architecture i386
clang: error: linker command failed with exit code 1 (use -v to see invocation)

Reproducible demo

npx react-native init AwesomeProject

Add Watch App for iOS App Target

Accept Defaults

Error building AwesomeProject for iPhone 11 Simulator

[iyegoroff]

I fixed similar error in my iOS app by removing "\"$(TOOLCHAIN_DIR)/usr/lib/swift-5.0/$(PLATFORM_NAME)\"", line from LIBRARY_SEARCH_PATHS in project.pbxproj file.

[Menardi]

I ran in to a similar issue when trying to create a home screen widget in Xcode 12 for iOS 14. The fix mentioned above didn’t work for me, but it set me on the right path. I’m posting my fix here in case others may find it useful!

For me, there were two steps to fixing this issue:

1. Removed all entries from LIBRARY_SEARCH_PATHS in the Project configuration
2. Add a new Swift file to the project (File > New > File > Swift), and call it whatever you want