Can you attach your project?

Comment by Edward Connell (JIRA)

UPDATE I attached a simple repro case.

1. build the project as HelloWorld (or whatever)
2. then from the LLDB CLI, set a breakpoint on line 5, then examine outputData

$ lldb HelloWorld
(lldb) target create "HelloWorld"
Current executable set to 'HelloWorld' (x86_64).
(lldb) br se --file main.swift --line 5
Breakpoint 1: where = HelloWorld`HelloWorld.fetch(outputData: inout Swift.Optional<HelloWorld.SomeStruct>) -> () + 28 at main.swift:5, address = 0x0000000000400b6c
(lldb) r
Process 14669 launched: '/home/ed/CLionProjects/untitled1/.build/debug/HelloWorld' (x86_64)
Process 14669 stopped

• thread [DON'T MERGE] Test pull request #1, name = 'HelloWorld', stop reason = breakpoint 1.1
  frame #0: 0x0000000000400b6c HelloWorld`fetch(outputData=some) at main.swift:5
  2
  3 func fetch(outputData: inout SomeStruct?) {
  4 outputData = SomeStruct()
  -> 5 }
  6
  7 var outData: SomeStruct?
  8
  Target 0: (HelloWorld) stopped.
  (lldb) fr var -O outputData
  lldb: /home/buildnode/disk2/workspace/oss-swift-4.0-package-linux-ubuntu-16_04/swift/lib/SIL/TypeLowering.cpp:1693: const swift::Lowering::TypeLowering &swift::Lowering::TypeConverter::getTypeLoweringForUncachedLoweredType(swift::Lowering::TypeConverter::TypeKey): Assertion `key.SubstType->isLegalSILType() && "type is not already lowered"' failed.
  Stack dump:
  0. HandleCommand(command = "fr var -O outputData")
  Aborted (core dumped)

Comment by Edward Connell (JIRA)

This still crashes LLDB with the Ubuntu 16.04 Swift 4.0 June 29th build. This is a blocking bug. Please please raise the priority on this. Thank you!

@swift-ci create

apple/swift-lldb#241