r317727 - [ObjC] Boxed strings should use the nullability from stringWithUTF8String's return type

[Alex Lorenz via cfe-commits]

Author: arphaman
Date: Wed Nov  8 13:33:15 2017
New Revision: 317727

URL: http://llvm.org/viewvc/llvm-project?rev=317727&view=rev
Log:
[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

Added:
    cfe/trunk/test/SemaObjC/transfer-boxed-string-nullability.m
Modified:
    cfe/trunk/lib/Sema/SemaExprObjC.cpp

Modified: cfe/trunk/lib/Sema/SemaExprObjC.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaExprObjC.cpp?rev=317727&r1=317726&r2=317727&view=diff
==============================================================================
--- cfe/trunk/lib/Sema/SemaExprObjC.cpp (original)
+++ cfe/trunk/lib/Sema/SemaExprObjC.cpp Wed Nov  8 13:33:15 2017
@@ -564,6 +564,13 @@ ExprResult Sema::BuildObjCBoxedExpr(Sour
       
       BoxingMethod = StringWithUTF8StringMethod;
       BoxedType = NSStringPointer;
+      // Transfer the nullability from method's return type.
+      Optional<NullabilityKind> Nullability =
+          BoxingMethod->getReturnType()->getNullability(Context);
+      if (Nullability)
+        BoxedType = Context.getAttributedType(
+            AttributedType::getNullabilityAttrKind(*Nullability), BoxedType,
+            BoxedType);
     }
   } else if (ValueType->isBuiltinType()) {
     // The other types we support are numeric, char and BOOL/bool. We could also

Added: cfe/trunk/test/SemaObjC/transfer-boxed-string-nullability.m
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaObjC/transfer-boxed-string-nullability.m?rev=317727&view=auto
==============================================================================
--- cfe/trunk/test/SemaObjC/transfer-boxed-string-nullability.m (added)
+++ cfe/trunk/test/SemaObjC/transfer-boxed-string-nullability.m Wed Nov  8 13:33:15 2017
@@ -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
+
+ at interface NSString
+
++ (NSString*
+#ifndef NOWARN
+  _Nullable
+#else
+  _Nonnull
+#endif
+) stringWithUTF8String:(const char*)x;
+
+ at end
+
+void takesNonNull(NSString * _Nonnull ptr);
+
+void testBoxedString() {
+  const char *str = "hey";
+  takesNonNull([NSString stringWithUTF8String:str]);
+  takesNonNull(@(str));
+#ifndef NOWARN
+  // expected-warning at -3 {{implicit conversion from nullable pointer 'NSString * _Nullable' to non-nullable pointer type 'NSString * _Nonnull'}}
+  // expected-warning at -3 {{implicit conversion from nullable pointer 'NSString * _Nullable' to non-nullable pointer type 'NSString * _Nonnull'}}
+#else
+  // expected-no-diagnostics
+#endif
+}