[IRGen] Mangling of nonisolated(nonsending) function types was introduced in Swift 6.2

We can't use mangled named when back-deploying earlier.

Author: DougGregor

lib/IRGen/GenReflection.cpp

@@ -204,9 +204,10 @@ getRuntimeVersionThatSupportsDemanglingType(CanType type) {
     Swift_5_5,
     Swift_6_0,
     Swift_6_1,
+    Swift_6_2,
 
     // Short-circuit if we find this requirement.
-    Latest = Swift_6_1
+    Latest = Swift_6_2
   };
 
   VersionRequirement latestRequirement = None;
@@ -223,6 +224,11 @@ getRuntimeVersionThatSupportsDemanglingType(CanType type) {
       auto isolation = fn->getIsolation();
       auto sendingResult = fn->hasSendingResult();
 
+      // The mangling for nonisolated(nonsending) function types was introduced
+      // in Swift 6.2.
+      if (isolation.isNonIsolatedCaller())
+        return addRequirement(Swift_6_2);
+
       // The Swift 6.1 runtime fixes a bug preventing successful demangling
       // when @isolated(any) or global actor isolation is combined with a
       // sending result.
@@ -290,6 +296,7 @@ getRuntimeVersionThatSupportsDemanglingType(CanType type) {
   });
 
   switch (latestRequirement) {
+  case Swift_6_2: return llvm::VersionTuple(6, 2);
   case Swift_6_1: return llvm::VersionTuple(6, 1);
   case Swift_6_0: return llvm::VersionTuple(6, 0);
   case Swift_5_5: return llvm::VersionTuple(5, 5);

test/IRGen/backward_deploy_nonisolated_nonsending_function_type.swift

@@ -0,0 +1,17 @@
+// RUN: %target-swift-frontend -target %target-cpu-apple-macos12 -emit-ir -o - -primary-file %s | %FileCheck %s
+// REQUIRES: concurrency
+// REQUIRES: OS=macosx
+
+func useGenericMetatype(_ type: Any.Type) { }
+
+// CHECK-LABEL: define hidden swiftcc void @"$s52backward_deploy_nonisolated_nonsending_function_type29testNonisolatedNonsendingTypeyyF"()
+func testNonisolatedNonsendingType() {
+  typealias Fn = nonisolated(nonsending) () async throws -> Int
+
+  // CHECK: call swiftcc %swift.metadata_response @"$sSiyYaKYCcMa"
+  // CHECK: call swiftcc void @"$s52backward_deploy_nonisolated_nonsending_function_type18useGenericMetatypeyyypXpF"
+  useGenericMetatype(Fn.self)
+}
+
+// CHECK-LABEL: define linkonce_odr hidden swiftcc %swift.metadata_response @"$sSiyYaKYCcMa"
+// CHECK: call ptr @swift_getExtendedFunctionTypeMetadata(i{{32|64}} 2768240640, {{i32|i64}} 0, ptr null, ptr null, ptr @"$sSiN"