Merge pull request swiftlang#38825 from nate-chandler/rdar81625544

[SIL] Fixed return index for call-as-async (BOOL, Error, Value) case.

Author: nate-chandler

lib/SIL/IR/AbstractionPattern.cpp

@@ -574,12 +574,14 @@ AbstractionPattern AbstractionPattern::getFunctionResultType() const {
         // If there's a single argument, abstract it according to its formal type
         // in the ObjC signature.
         unsigned callbackResultIndex = 0;
-        if (callbackErrorIndex && callbackResultIndex >= *callbackErrorIndex)
-          ++callbackResultIndex;
-        if (callbackErrorFlagIndex
-            && callbackResultIndex >= *callbackErrorFlagIndex)
-          ++callbackResultIndex;
-
+        for (auto index : indices(callbackParamTy->getParamTypes())) {
+          if (callbackErrorIndex && index == *callbackErrorIndex)
+            continue;
+          if (callbackErrorFlagIndex && index == *callbackErrorFlagIndex)
+            continue;
+          callbackResultIndex = index;
+          break;
+        }
         auto clangResultType = callbackParamTy
           ->getParamType(callbackResultIndex)
           .getTypePtr();

validation-test/compiler_crashers_2_fixed/rdar81617749.swift

@@ -25,9 +25,8 @@ func run(on object: PFXObject) async throws {
   // CHECK: performSingleBothy13
   print(try await object.performSingleBothy13()())
 
-  // Reenable with rdar://81625544
-  // CHECK  performSingleBothy21
-  //  print(try await object.performSingleBothy21()())
+  // CHECK: performSingleBothy21
+  print(try await object.performSingleBothy21()())
 
   // CHECK: performSingleBothy23
   print(try await object.performSingleBothy23()())