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[Concurrency] Fix async-main crash #36201

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Merged
merged 2 commits into from
Mar 3, 2021
Merged

[Concurrency] Fix async-main crash #36201

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638a5b6
Fix crash with async main and no conc module
etcwilde Feb 27, 2021
6d18260
Add test for non-concurrency async-main
etcwilde Feb 27, 2021
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3 changes: 3 additions & 0 deletions include/swift/AST/DiagnosticsSema.def
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Original file line number Diff line number Diff line change
Expand Up @@ -4379,6 +4379,9 @@ ERROR(actorindependent_local_var,none,
ERROR(concurrency_lib_missing,none,
"missing '%0' declaration, probably because the '_Concurrency' "
"module was not imported", (StringRef))
ERROR(async_main_no_concurrency,none,
"'_Concurrency' module not imported, required for async main", ())

ERROR(enqueue_partial_task_not_in_context,none,
"'enqueue(partialTask:)' can only be implemented in the definition of "
"actor class %0", (Type))
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12 changes: 11 additions & 1 deletion lib/Sema/TypeCheckAttr.cpp
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Expand Up @@ -1835,7 +1835,17 @@ synthesizeMainBody(AbstractFunctionDecl *fn, void *arg) {
// Resulting $main looks like:
// $main() { _runAsyncMain(main) }
auto *concurrencyModule = context.getLoadedModule(context.Id_Concurrency);
assert(concurrencyModule != nullptr && "Failed to find Concurrency module");
if (!concurrencyModule) {
context.Diags.diagnose(mainFunction->getAsyncLoc(),
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We may want a comment relating how this fixes the crash because _Concurrency implicitly gets imported when -enable-experimental-concurrency is passed in, but doesn't when it's not. If that changes, the crash comes back.

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It'll work the way it is now, but how about checking for !concurrencyModule below instead of -enable-experimental-concurrency? That would avoid the crash if the module doesn't get loaded for any reason.

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Okay, now checks against the concurrency module. Also added a test passing both -enable-experimental-concurrency and -parse-stdlib since that won't implicitly import _Concurrency either.

diag::async_main_no_concurrency);
auto result = new (context) ErrorExpr(mainFunction->getSourceRange());
SmallVector<ASTNode, 1> stmts;
stmts.push_back(result);
auto body = BraceStmt::create(context, SourceLoc(), stmts,
SourceLoc(), /*Implicit*/true);

return std::make_pair(body, /*typechecked*/true);
}

SmallVector<ValueDecl *, 1> decls;
concurrencyModule->lookupQualified(
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8 changes: 8 additions & 0 deletions test/Concurrency/async_main_no_concurrency.swift
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@@ -0,0 +1,8 @@
// RUN: %target-typecheck-verify-swift -parse-as-library %s
// RUN: %target-typecheck-verify-swift -parse-as-library -enable-experimental-concurrency -parse-stdlib %s

@main struct Main {
// expected-error@+1:22{{'_Concurrency' module not imported, required for async main}}
static func main() async {
}
}