--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/clang/test/Sema/attr-musttail.m	Tue Jun 08 06:07:14 2021 +0900
@@ -0,0 +1,26 @@
+// RUN: %clang_cc1 -fsyntax-only -fblocks -Wno-objc-root-class -verify %s
+
+void TestObjcBlock(void) {
+  void (^x)(void) = ^(void) {
+    __attribute__((musttail)) return TestObjcBlock(); // expected-error{{'musttail' attribute cannot be used from a block}}
+  };
+  __attribute__((musttail)) return x();
+}
+
+void ReturnsVoid(void);
+void TestObjcBlockVar(void) {
+  __block int i = 0;                              // expected-note{{jump exits scope of __block variable}}
+  __attribute__((musttail)) return ReturnsVoid(); // expected-error{{cannot perform a tail call from this return statement}}
+}
+
+__attribute__((objc_root_class))
+@interface TestObjcClass
+@end
+
+@implementation TestObjcClass
+
+- (void)testObjCMethod {
+  __attribute__((musttail)) return ReturnsVoid(); // expected-error{{'musttail' attribute cannot be used from an Objective-C function}}
+}
+
+@end