[Concurrency] SILGenModule::emitEntryPoint crashes when exit hasn't been imported

[ian-twilightcoder]

If exit hasn't been imported, SILGenModule::emitEntryPoint crashes because it doesn't synthesize an exit function like SILGenFunction::emitCallToMain does. Make it do so.

rdar://122413238

[etcwilde]

Hmm, I guess we don't have any test cases that test async top-level code in an environment that doesn't have an exit imported already. I think we should be able to create one with -parse-stdlib and maybe a few other flags.
Something like swiftc -parse-stdlib <foo.swift> and the below should at least get close to repro'ing the assert:

import _Concurrency
func foo() async { }
await foo()

[ian-twilightcoder]

Hmm, I guess we don't have any test cases that test async top-level code in an environment that doesn't have an exit imported already. I think we should be able to create one with -parse-stdlib and maybe a few other flags. Something like swiftc -parse-stdlib <foo.swift> and the below should at least get close to repro'ing the assert:

import _Concurrency
func foo() async { }
await foo()

Would this work from async_main_no_concurrency.swift?

// RUN: %target-typecheck-verify-swift -parse-as-library -disable-availability-checking -parse-stdlib

Should I also add a @main struct?

[etcwilde]

Would this work from async_main_no_concurrency.swift?

// RUN: %target-typecheck-verify-swift -parse-as-library -disable-availability-checking -parse-stdlib

Something like that, yeah.

Should I also add a @main struct?

To test emitEntryPoint, no. We want to emit an async top-level code snippet which uses that path instead of emitAsyncMain.

[ian-twilightcoder]

Would this work from async_main_no_concurrency.swift?
// RUN: %target-typecheck-verify-swift -parse-as-library -disable-availability-checking -parse-stdlib

Something like that, yeah.

Should I also add a @main struct?

To test emitEntryPoint, no. We want to emit an async top-level code snippet which uses that path instead of emitAsyncMain.

We should probably have an explicit test for both though. Can we do that in a single test, i.e. with a top level @main struct and a top level async func, or do we need two tests for that?

[etcwilde]

We should probably have an explicit test for both though. Can we do that in a single test, i.e. with a top level @main struct and a top level async func, or do we need two tests for that?

I believe it needs to be in two tests since the #if directives don't just delete syntax like in C. The @main will not parse, even if we do something like this:

// RUN: %target-typecheck-verify-swift -parse-as-library -disable-availability-checking -parse-stdlib
// RUN: %target-typecheck-verify-swift -disable-availability-checking -parse-stdlib -DTOP_LEVEL_TEST

func foo() async {}

#if TOP_LEVEL_TEST
await foo()
#else
@main struct Main {
  static func main() async {
    await foo()
  }
}

[ian-twilightcoder]

@swift-ci smoke test

[ian-twilightcoder]

@swift-ci smoke test