[ObjC] Emit a boxed expression as a compile-time constant if the

expression inside the parentheses is a valid UTF-8 string literal.

Previously clang emitted an expression like @("abc") as a message send
to stringWithUTF8String. This commit makes clang emit the boxed
expression as a compile-time constant instead.

This commit also has the effect of silencing the nullable-to-nonnull
conversion warning clang started emitting after r317727, which
originally motivated this commit (see https://oleb.net/2018/@keypath).

rdar://problem/42684601

Differential Revision: https://reviews.llvm.org/D58729

llvm-svn: 355662

3 files changed, 32 insertions, 7 deletions

diff --git a/clang/test/SemaObjC/boxing-illegal.m b/clang/test/SemaObjC/boxing-illegal.m
index 59b5c8b710d..329873ac6ad 100644
--- a/clang/test/SemaObjC/boxing-illegal.m
+++ b/clang/test/SemaObjC/boxing-illegal.m
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -fsyntax-only -verify -Wattributes %s
+// RUN: %clang_cc1 -fsyntax-only -verify -Wattributes -fpascal-strings %s
 
 typedef long NSInteger;
 typedef unsigned long NSUInteger;
@@ -57,6 +57,19 @@ void testEnum(void *p) {
   box = @(*(enum ForwE*)p); // expected-error {{incomplete type 'enum ForwE' used in a boxed expression}}
 }
 
+@interface NSString
+@end
+
+void testStringLiteral() {
+  NSString *s;
+  s = @("abc");
+  s = @(u8"abc");
+  s = @(u"abc"); // expected-error {{illegal type 'unsigned short *' used in a boxed expression}}
+  s = @(U"abc"); // expected-error {{illegal type 'unsigned int *' used in a boxed expression}}
+  s = @(L"abc"); // expected-error {{illegal type 'int *' used in a boxed expression}}
+  s = @("\pabc"); // expected-error {{illegal type 'unsigned char *' used in a boxed expression}}
+}
+
 // rdar://13333205
 @class NSMutableDictionary;
 
diff --git a/clang/test/SemaObjC/objc-literal-sig.m b/clang/test/SemaObjC/objc-literal-sig.m
index 86f42d3abca..48f69165efb 100644
--- a/clang/test/SemaObjC/objc-literal-sig.m
+++ b/clang/test/SemaObjC/objc-literal-sig.m
@@ -39,6 +39,8 @@ typedef _Bool BOOL;
 
 // All tests are doubled to make sure that a bad method is not saved
 // and then used un-checked.
+const char *getStr(void);
+
 void test_sig() {
   (void)@__objc_yes; // expected-error{{literal construction method 'numberWithBool:' has incompatible signature}}
   (void)@__objc_yes; // expected-error{{literal construction method 'numberWithBool:' has incompatible signature}}
@@ -46,6 +48,6 @@ void test_sig() {
   id array2 = @[ @17 ]; // expected-error{{literal construction method 'arrayWithObjects:count:' has incompatible signature}}
   id dict = @{ @"hello" : @17 }; // expected-error{{literal construction method 'dictionaryWithObjects:forKeys:count:' has incompatible signature}}
   id dict2 = @{ @"hello" : @17 }; // expected-error{{literal construction method 'dictionaryWithObjects:forKeys:count:' has incompatible signature}}
-  id str = @("hello"); // expected-error{{literal construction method 'stringWithUTF8String:' has incompatible signature}}
-  id str2 = @("hello"); // expected-error{{literal construction method 'stringWithUTF8String:' has incompatible signature}}
+  id str = @(getStr()); // expected-error{{literal construction method 'stringWithUTF8String:' has incompatible signature}}
+  id str2 = @(getStr()); // expected-error{{literal construction method 'stringWithUTF8String:' has incompatible signature}}
 }
diff --git a/clang/test/SemaObjC/transfer-boxed-string-nullability.m b/clang/test/SemaObjC/transfer-boxed-string-nullability.m
index 42604ef4a6a..a3b6832be46 100644
--- a/clang/test/SemaObjC/transfer-boxed-string-nullability.m
+++ b/clang/test/SemaObjC/transfer-boxed-string-nullability.m
@@ -16,13 +16,23 @@
 void takesNonNull(NSString * _Nonnull ptr);
 
 void testBoxedString() {
+  // No diagnostic emitted as this doesn't need a stringWithUTF8String message
+  // send.
+  takesNonNull(@("hey"));
+  takesNonNull(@(u8"hey"));
+
+  // If the string isn't a valid UTF-8 string, a diagnostic is emitted since the
+  // boxed expression turns into a message send.
+  takesNonNull(@(u8"\xFF")); // expected-warning {{string is ill-formed as UTF-8}}
+  takesNonNull(@(u8"\xC0\x80")); // expected-warning {{string is ill-formed as UTF-8}}
+
   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
+  // expected-warning@-7 {{implicit conversion from nullable pointer 'NSString * _Nullable' to non-nullable pointer type 'NSString * _Nonnull'}}
+  // expected-warning@-7 {{implicit conversion from nullable pointer 'NSString * _Nullable' to non-nullable pointer type 'NSString * _Nonnull'}}
+  // expected-warning@-5 {{implicit conversion from nullable pointer 'NSString * _Nullable' to non-nullable pointer type 'NSString * _Nonnull'}}
+  // expected-warning@-5 {{implicit conversion from nullable pointer 'NSString * _Nullable' to non-nullable pointer type 'NSString * _Nonnull'}}
 #endif
 }