Compilation failure with Swift 5.1

[djones6]

Attempting to build BlueSignals on Linux (or a project which depends on it - such as Kitura) with the latest Swift 5.1 snapshot (swift-5.1-DEVELOPMENT-SNAPSHOT-2019-04-17-a) fails with:

Incorrect reconstructed type for $sSay7SignalsAAC6SignalO6signal_ys5Int32VXC6actiontGD
Original type:
(bound_generic_struct_type decl=Swift.(file).Array
  (tuple_type num_elements=2
    (tuple_type_elt name=signal
      (enum_type decl=Signals.(file).Signals.Signal@/home/djones6/swift501/Kitura/.build/checkouts/BlueSignals/Sources/Signals/Signals.swift:38:14
        (parent=class_type decl=Signals.(file).Signals@/home/djones6/swift501/Kitura/.build/checkouts/BlueSignals/Sources/Signals/Signals.swift:31:14)))
    (tuple_type_elt name=action
      (function_type representation=c escaping
        (input=function_params num_params=1
          (param
            (struct_type decl=Swift.(file).Int32)))
        (output=tuple_type num_elements=0)))))
Reconstructed type:
(bound_generic_struct_type decl=Swift.(file).Array
  (tuple_type num_elements=2
    (tuple_type_elt name=signal
      (enum_type decl=Signals.(file).Signals.Signal@/home/djones6/swift501/Kitura/.build/checkouts/BlueSignals/Sources/Signals/Signals.swift:38:14
        (parent=class_type decl=Signals.(file).Signals@/home/djones6/swift501/Kitura/.build/checkouts/BlueSignals/Sources/Signals/Signals.swift:31:14)))
    (tuple_type_elt name=action
      (function_type representation=c
        (input=function_params num_params=1
          (param
            (struct_type decl=Swift.(file).Int32)))
        (output=tuple_type num_elements=0)))))
Stack dump:
0.      Program arguments: /home/djones6/.swiftenv/versions/5.1-DEVELOPMENT-SNAPSHOT-2019-04-17-a/usr/bin/swift -frontend -c -primary-file /home/djones6/swift501/Kitura/.build/checkouts/BlueSignals/Sources/Signals/Signals.swift -emit-module-path /home/djones6/swift501/Kitura/.build/x86_64-unknown-linux/debug/Signals.build/Signals~partial.swiftmodule -emit-module-doc-path /home/djones6/swift501/Kitura/.build/x86_64-unknown-linux/debug/Signals.build/Signals~partial.swiftdoc -emit-dependencies-path /home/djones6/swift501/Kitura/.build/x86_64-unknown-linux/debug/Signals.build/Signals.d -emit-reference-dependencies-path /home/djones6/swift501/Kitura/.build/x86_64-unknown-linux/debug/Signals.build/Signals.swiftdeps -target x86_64-unknown-linux -disable-objc-interop -sdk / -I /home/djones6/swift501/Kitura/.build/x86_64-unknown-linux/debug -enable-testing -g -module-cache-path /home/djones6/swift501/Kitura/.build/x86_64-unknown-linux/debug/ModuleCache -swift-version 5 -Onone -D SWIFT_PACKAGE -D DEBUG -color-diagnostics -enable-anonymous-context-mangled-names -parse-as-library -module-name Signals -o /home/djones6/swift501/Kitura/.build/x86_64-unknown-linux/debug/Signals.build/Signals.swift.o -index-store-path /home/djones6/swift501/Kitura/.build/x86_64-unknown-linux/debug/index/store -index-system-modules
1.      While emitting IR SIL function "@$s7SignalsAAC4trap7signalsySayAB6SignalO6signal_ys5Int32VXC6actiontG_tFZ".
 for 'trap(signals:)' (at /home/djones6/swift501/Kitura/.build/checkouts/BlueSignals/Sources/Signals/Signals.swift:123:9)
/home/djones6/.swiftenv/versions/5.1-DEVELOPMENT-SNAPSHOT-2019-04-17-a/usr/bin/swift[0x48cca44]
/home/djones6/.swiftenv/versions/5.1-DEVELOPMENT-SNAPSHOT-2019-04-17-a/usr/bin/swift[0x48ca660]
/home/djones6/.swiftenv/versions/5.1-DEVELOPMENT-SNAPSHOT-2019-04-17-a/usr/bin/swift[0x48cce68]
/lib/x86_64-linux-gnu/libpthread.so.0(+0x11390)[0x7fdfe639c390]
/lib/x86_64-linux-gnu/libc.so.6(gsignal+0x38)[0x7fdfe4adb428]
/lib/x86_64-linux-gnu/libc.so.6(abort+0x16a)[0x7fdfe4add02a]
/home/djones6/.swiftenv/versions/5.1-DEVELOPMENT-SNAPSHOT-2019-04-17-a/usr/bin/swift[0x6e6689]
/home/djones6/.swiftenv/versions/5.1-DEVELOPMENT-SNAPSHOT-2019-04-17-a/usr/bin/swift[0x6e6e5f]
/home/djones6/.swiftenv/versions/5.1-DEVELOPMENT-SNAPSHOT-2019-04-17-a/usr/bin/swift[0x6e6b12]
/home/djones6/.swiftenv/versions/5.1-DEVELOPMENT-SNAPSHOT-2019-04-17-a/usr/bin/swift[0x6de076]
/home/djones6/.swiftenv/versions/5.1-DEVELOPMENT-SNAPSHOT-2019-04-17-a/usr/bin/swift[0x6ded3f]
/home/djones6/.swiftenv/versions/5.1-DEVELOPMENT-SNAPSHOT-2019-04-17-a/usr/bin/swift[0x6f03c3]
/home/djones6/.swiftenv/versions/5.1-DEVELOPMENT-SNAPSHOT-2019-04-17-a/usr/bin/swift[0x61c344]
/home/djones6/.swiftenv/versions/5.1-DEVELOPMENT-SNAPSHOT-2019-04-17-a/usr/bin/swift[0x5865f8]
/home/djones6/.swiftenv/versions/5.1-DEVELOPMENT-SNAPSHOT-2019-04-17-a/usr/bin/swift[0x586cd7]
/home/djones6/.swiftenv/versions/5.1-DEVELOPMENT-SNAPSHOT-2019-04-17-a/usr/bin/swift[0x508e94]
/home/djones6/.swiftenv/versions/5.1-DEVELOPMENT-SNAPSHOT-2019-04-17-a/usr/bin/swift[0x50451f]
/home/djones6/.swiftenv/versions/5.1-DEVELOPMENT-SNAPSHOT-2019-04-17-a/usr/bin/swift[0x49fbdd]
/lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xf0)[0x7fdfe4ac6830]
/home/djones6/.swiftenv/versions/5.1-DEVELOPMENT-SNAPSHOT-2019-04-17-a/usr/bin/swift[0x49f759]

This seems to relate to the @escaping attribute, and the various trap() function signatures. Specifically, there is one function that takes an array of (Signal,SigActionHandler) tuples, where the SigActionHandler is not explicitly marked as @escaping, however this is then passed to another trap() function where it is escaping.

I couldn't find a syntax that allows you to mark the SigActionHandler that is embedded in the tuple type as escaping, and to be honest I'm not sure how this currently compiles - the fact that it blows up (rather than producing a proper error) on 5.1 suggests it might be a compiler issue, but I'm not really sure.

[billabt]

I don't think this is a problem (except maybe with the compiler). Early in Swift 4.2 snapshot cycle, I had virtually the same thing happen to me. The compiler would dump on that particular function. Since it was a compiler crash rather than an error, I reported it to Apple using the BlueSignals project as an example. They fixed it rather quickly. I'd say watch it and see if it continues to crash with subsequent snapshots and if so, file another bug report.

[djones6]

This still fails on the latest snapshot (5.1-DEVELOPMENT-SNAPSHOT-2019-05-29-a). It is already reported under SR-10335, I'll add a comment there.

[ianpartridge]

Hopefully fixed by apple/swift#25423

[ianpartridge]

Fixed!