[ObjC] Boxed strings should use the nullability from stringWithUTF8String's return type

Objective-C NSString has a class method stringWithUTF8String that creates a new
NSString from a C string. Objective-C box expression @(...) can be used to
create an NSString instead of invoking the stringWithUTF8String method directly
(The compiler lowers it down to the invocation though). This commit ensures that
the type of @(string-value) gets the same nullability attributes as the return
type of stringWithUTF8String to ensure that the diagnostics are consistent
between the two.

rdar://33847186

Differential Revision: https://reviews.llvm.org/D39762


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@317727 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 28 insertions, 0 deletions

diff --git a/test/SemaObjC/transfer-boxed-string-nullability.m b/test/SemaObjC/transfer-boxed-string-nullability.m
new file mode 100644
index 0000000000..42604ef4a6
--- /dev/null
+++ b/test/SemaObjC/transfer-boxed-string-nullability.m
@@ -0,0 +1,28 @@
+// RUN: %clang_cc1 -fblocks -fobjc-arc -Wnullable-to-nonnull-conversion -fsyntax-only -verify -Wno-objc-root-class %s
+// RUN: %clang_cc1 -fblocks -fobjc-arc -Wnullable-to-nonnull-conversion -fsyntax-only -verify -Wno-objc-root-class -DNOWARN %s
+
+@interface NSString
+
++ (NSString*
+#ifndef NOWARN
+  _Nullable
+#else
+  _Nonnull
+#endif
+) stringWithUTF8String:(const char*)x;
+
+@end
+
+void takesNonNull(NSString * _Nonnull ptr);
+
+void testBoxedString() {
+  const char *str = "hey";
+  takesNonNull([NSString stringWithUTF8String:str]);
+  takesNonNull(@(str));
+#ifndef NOWARN
+  // expected-warning@-3 {{implicit conversion from nullable pointer 'NSString * _Nullable' to non-nullable pointer type 'NSString * _Nonnull'}}
+  // expected-warning@-3 {{implicit conversion from nullable pointer 'NSString * _Nullable' to non-nullable pointer type 'NSString * _Nonnull'}}
+#else
+  // expected-no-diagnostics
+#endif
+}