[PATCH] Extend -Wstring-conversion to catch NSString* to bool conversion

[Richard Trieu]

A fix for half of PR18050, making -Wstring-conversion catch cases where an NSString* is converted to true.

I don't normally work with Objective C so let me know if I am missing any test cases.

http://llvm-reviews.chandlerc.com/D2608

Files:
  lib/Sema/SemaChecking.cpp
  test/SemaObjCXX/warn-string-conversion.mm

Index: lib/Sema/SemaChecking.cpp
===================================================================
--- lib/Sema/SemaChecking.cpp
+++ lib/Sema/SemaChecking.cpp
@@ -5327,7 +5327,7 @@
 
   // Diagnose implicit casts to bool.
   if (Target->isSpecificBuiltinType(BuiltinType::Bool)) {
-    if (isa<StringLiteral>(E))
+    if (isa<StringLiteral>(E) || isa<ObjCStringLiteral>(E))
       // Warn on string literal to bool.  Checks for string literals in logical
       // expressions, for instances, assert(0 && "error here"), are prevented
       // by a check in AnalyzeImplicitConversions().
@@ -5688,7 +5688,8 @@
       continue;
 
     if (IsLogicalOperator &&
-        isa<StringLiteral>(ChildExpr->IgnoreParenImpCasts()))
+        (isa<StringLiteral>(ChildExpr->IgnoreParenImpCasts()) ||
+         isa<ObjCStringLiteral>(ChildExpr->IgnoreParenImpCasts())))
       // Ignore checking string literals that are in logical operators.
       continue;
     AnalyzeImplicitConversions(S, ChildExpr, CC);
Index: test/SemaObjCXX/warn-string-conversion.mm
===================================================================
--- test/SemaObjCXX/warn-string-conversion.mm
+++ test/SemaObjCXX/warn-string-conversion.mm
@@ -0,0 +1,31 @@
+// RUN: %clang_cc1 -fsyntax-only -Wstring-conversion -verify %s
+
+// Warn on cases where a string literal is converted into a bool.
+// An exception is made for this in logical operators.
+void assert(bool condition);
+void test0() {
+  bool b0 = "hi"; // expected-warning{{implicit conversion turns string literal into bool: 'const char [3]' to 'bool'}}
+  b0 = ""; // expected-warning{{implicit conversion turns string literal into bool: 'const char [1]' to 'bool'}}
+  b0 = 0 && "";
+  assert("error"); // expected-warning{{implicit conversion turns string literal into bool: 'const char [6]' to 'bool'}}
+  assert(0 && "error");
+
+  while("hi") {} // expected-warning{{implicit conversion turns string literal into bool: 'const char [3]' to 'bool'}}
+  do {} while("hi"); // expected-warning{{implicit conversion turns string literal into bool: 'const char [3]' to 'bool'}}
+  for (;"hi";); // expected-warning{{implicit conversion turns string literal into bool: 'const char [3]' to 'bool'}}
+  if("hi") {} // expected-warning{{implicit conversion turns string literal into bool: 'const char [3]' to 'bool'}}
+}
+
+void test1() {
+  bool b0 = @"hi"; // expected-warning{{implicit conversion turns string literal into bool: 'NSString *' to 'bool'}}
+  b0 = @""; // expected-warning{{implicit conversion turns string literal into bool: 'NSString *' to 'bool'}}
+  b0 = 0 && @"";
+  assert(@"error"); // expected-warning{{implicit conversion turns string literal into bool: 'NSString *' to 'bool'}}
+  assert(0 && @"error");
+
+  while(@"hi") {} // expected-warning{{implicit conversion turns string literal into bool: 'NSString *' to 'bool'}}
+  do {} while(@"hi"); // expected-warning{{implicit conversion turns string literal into bool: 'NSString *' to 'bool'}}
+  for (;@"hi";); // expected-warning{{implicit conversion turns string literal into bool: 'NSString *' to 'bool'}}
+  if(@"hi") {} // expected-warning{{implicit conversion turns string literal into bool: 'NSString *' to 'bool'}}
+}
+
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