Merge pull request #84665 from egorzhdan/egorzhdan/frt-objc-class

[cxx-interop] Avoid spurious references to `_OBJC_CLASS` symbols for C++ foreign reference types

Author: egorzhdan

lib/AST/Type.cpp

@@ -4409,6 +4409,12 @@ bool Type::findIf(llvm::function_ref<bool(Type)> pred) const {
 }
 
 TypeTraitResult TypeBase::canBeClass() {
+  // Foreign reference types are represented as Swift classes in the AST,
+  // however, they use custom retain/release operations, and therefore aren't
+  // AnyObjects.
+  if (isForeignReferenceType())
+    return TypeTraitResult::IsNot;
+
   // Any bridgeable object type can be a class.
   if (isBridgeableObjectType())
     return TypeTraitResult::Is;

test/Interop/Cxx/foreign-reference/array-of-classes.swift

@@ -58,6 +58,15 @@ func go() {
     y.append(x)
 // CHECK: 1
     print(y.count)
+
+    var loopCount = 0 
+    for it in y {
+// CHECK: RefType()
+        print(it)
+        loopCount += 1
+    }
+// CHECK: 1
+    print(loopCount)
 }
 
 go()