[rbi] Fix a thinko where while finding closure uses, I was not checking if functions had a body when looking for arguments.

rdar://145089562

Author: gottesmm

lib/SILOptimizer/Mandatory/SendNonSendable.cpp

@@ -238,7 +238,7 @@ findClosureUse(Operand *initialOperand) {
       return {};
 
     auto *f = as.getCalleeFunction();
-    if (!f)
+    if (!f || f->empty())
       return {};
 
     unsigned argumentIndex = as.getCalleeArgIndex(*initialOperand);
@@ -280,7 +280,7 @@ findClosureUse(Operand *initialOperand) {
     // See if we have a callee function. In such a case, find our operand in the
     // callee and visit its uses.
     if (auto as = dyn_cast<PartialApplyInst>(op->getUser())) {
-      if (auto *f = as->getCalleeFunction()) {
+      if (auto *f = as->getCalleeFunction(); f && !f->empty()) {
         auto *fArg = f->getArgument(ApplySite(as).getCalleeArgIndex(*op));
         for (auto *use : fArg->getUses()) {
           if (visitedOperand.insert(use).second)
@@ -294,7 +294,7 @@ findClosureUse(Operand *initialOperand) {
     // immediately invoked. In such a case, we can emit a better diagnostic in
     // the called closure.
     if (auto fas = FullApplySite::isa(op->getUser())) {
-      if (auto *f = fas.getCalleeFunction()) {
+      if (auto *f = fas.getCalleeFunction(); f && !f->empty()) {
         auto *fArg = cast<SILFunctionArgument>(
             f->getArgument(fas.getCalleeArgIndex(*op)));
         if (fArg->isClosureCapture()) {

test/Concurrency/transfernonsendable.swift

@@ -1933,3 +1933,14 @@ func testIndirectAndDirectSendingResultsWithGlobalActor() async {
     _ = ns2
   }
 }
+
+// We used to not check if bodies were not empty when emitting the error for
+// using result in the throwing task group. Make sure we do not crash.
+func testFunctionIsNotEmpty(input: SendableKlass) async throws {
+  var result: [SendableKlass] = []
+  try await withThrowingTaskGroup(of: Void.self) { taskGroup in // expected-warning {{no calls to throwing functions occur within 'try' expression}}
+    taskGroup.addTask { // expected-tns-warning {{passing closure as a 'sending' parameter risks causing data races between code in the current task and concurrent execution of the closure}}
+      result.append(input) // expected-tns-note {{closure captures reference to mutable var 'result' which is accessible to code in the current task}}
+    }
+  }
+}