[clang-tidy/google-readability-casting] Disable check for Objective-C++

[benhamilton]

Summary

Previously, google-readability-casting was disabled for Objective-C.

The Google Objective-C++ style allows both Objective-C and
C++ style in the same file. Since clang-tidy doesn't have a good
way to allow multiple styles per file, this disables the
check for Objective-C++.

Test Plan: New tests added. Ran tests with:

% make -j16 check-clang-tools
Before diff, confirmed tests failed:
https://reviews.llvm.org/P8081
After diff, confirrmed tests passed.

[benhamilton]

An alternative implementation would be to allow C-style casts (either always or only for ObjC objects) within Objective-C methods inside Objective-C++ files, but that may get messy with things like shared macros.

[benhamilton]

• Change to simply disable check for Objective-C++

[benhamilton]

After discussion, I changed this diff to simply disable the check altogether for Objective-C++.

[alexfh]

LG

[stephanemoore]

clang-tidy/google/AvoidCStyleCastsCheck.cpp

103–104 ↗

(On Diff #147102)

In the future it would probably be good to allow configuring whether or not this is disabled but I think that disabling it for Objective-C++ completely in the interim is a positive change.

[benhamilton]

clang-tidy/google/AvoidCStyleCastsCheck.cpp

103–104 ↗

(On Diff #147102)

Agreed. Filed https://bugs.llvm.org/show_bug.cgi?id=37489 to follow up.

clang-tools-extra/trunk/clang-tidy/google/AvoidCStyleCastsCheck.cpp

if (CastExpr->getCastKind() == CK_NoOp && !FnToFnCast) {
     if (SourceTypeAsWritten == DestTypeAsWritten) {
       diag(CastExpr->getLocStart(), "redundant cast to the same type")
           << FixItHint::CreateRemoval(ReplaceRange);
       return;
     }
   }
 
   // The rest of this check is only relevant to C++.
-  if (!getLangOpts().CPlusPlus)
+  // We also disable it for Objective-C++.
+  if (!getLangOpts().CPlusPlus || getLangOpts().ObjC1 || getLangOpts().ObjC2)
     return;
   // Ignore code inside extern "C" {} blocks.
   if (!match(expr(hasAncestor(linkageSpecDecl())), *CastExpr, *Result.Context)
            .empty())
     return;
   // Ignore code in .c files and headers included from them, even if they are
   // compiled as C++.
   if (getCurrentMainFile().endswith(".c"))

clang-tools-extra/trunk/test/clang-tidy/google-readability-casting.mm

+// RUN: clang-tidy %s -checks=-*,google-readability-casting -- \
+// RUN:   -xobjective-c++ -fobjc-abi-version=2 -fobjc-arc | count 0
+
+// Note: this test expects no diagnostics, but FileCheck cannot handle that,
+// hence the use of | count 0.
+
+bool g() { return false; }
+
+enum Enum { Enum1 };
+struct X {};
+struct Y : public X {};
+
+void f(int a, double b, const char *cpc, const void *cpv, X *pX) {
+
+  typedef const char *Typedef1;
+  typedef const char *Typedef2;
+  Typedef1 t1;
+  (Typedef2)t1;
+  (const char*)t1;
+  (Typedef1)cpc;
+
+  typedef char Char;
+  char *pc;
+  Char *pChar = (Char*)pc;
+
+  (Char)*cpc;
+
+  (char)*pChar;
+
+  (const char*)cpv;
+
+  char *pc2 = (char*)(cpc + 33);
+
+  const char &crc = *cpc;
+  char &rc = (char&)crc;
+
+  char &rc2 = (char&)*cpc;
+
+  char ** const* const* ppcpcpc;
+  char ****ppppc = (char****)ppcpcpc;
+
+  char ***pppc = (char***)*(ppcpcpc);
+
+  char ***pppc2 = (char***)(*ppcpcpc);
+
+  char *pc5 = (char*)(const char*)(cpv);
+
+  int b1 = (int)b;
+  b1 = (const int&)b;
+
+  b1 = (int) b;
+
+  b1 = (int)         b;
+
+  b1 = (int) (b);
+
+  b1 = (int)         (b);
+
+  Y *pB = (Y*)pX;
+  Y &rB = (Y&)*pX;
+
+  const char *pc3 = (const char*)cpv;
+
+  char *pc4 = (char*)cpv;
+
+  b1 = (int)Enum1;
+
+  Enum e = (Enum)b1;
+
+  int b2 = int(b);
+  int b3 = static_cast<double>(b);
+  int b4 = b;
+  double aa = a;
+  (void)b2;
+  return (void)g();
+}
+
+template <typename T>
+void template_function(T t, int n) {
+  int i = (int)t;
+}
+
+template <typename T>
+struct TemplateStruct {
+  void f(T t, int n) {
+    int k = (int)t;
+  }
+};
+
+void test_templates() {
+  template_function(1, 42);
+  template_function(1.0, 42);
+  TemplateStruct<int>().f(1, 42);
+  TemplateStruct<double>().f(1.0, 42);
+}
+
+extern "C" {
+void extern_c_code(const char *cpc) {
+  char *pc = (char*)cpc;
+}
+}
+
+#define CAST(type, value) (type)(value)
+void macros(double d) {
+  int i = CAST(int, d);
+}
+
+enum E { E1 = 1 };
+template <E e>
+struct A {
+  // Usage of template argument e = E1 is represented as (E)1 in the AST for
+  // some reason. We have a special treatment of this case to avoid warnings
+  // here.
+  static const E ee = e;
+};
+struct B : public A<E1> {};
+
+
+void overloaded_function();
+void overloaded_function(int);
+
+template<typename Fn>
+void g(Fn fn) {
+  fn();
+}
+
+void function_casts() {
+  typedef void (*FnPtrVoid)();
+  typedef void (&FnRefVoid)();
+  typedef void (&FnRefInt)(int);
+
+  g((void (*)())overloaded_function);
+  g((void (*)())&overloaded_function);
+  g((void (&)())overloaded_function);
+
+  g((FnPtrVoid)overloaded_function);
+  g((FnPtrVoid)&overloaded_function);
+  g((FnRefVoid)overloaded_function);
+
+  FnPtrVoid fn0 = (void (*)())&overloaded_function;
+  FnPtrVoid fn1 = (void (*)())overloaded_function;
+  FnPtrVoid fn1a = (FnPtrVoid)overloaded_function;
+  FnRefInt fn2 = (void (&)(int))overloaded_function;
+  auto fn3 = (void (*)())&overloaded_function;
+  auto fn4 = (void (*)())overloaded_function;
+  auto fn5 = (void (&)(int))overloaded_function;
+
+  void (*fn6)() = (void (*)())&overloaded_function;
+  void (*fn7)() = (void (*)())overloaded_function;
+  void (*fn8)() = (FnPtrVoid)overloaded_function;
+  void (&fn9)(int) = (void (&)(int))overloaded_function;
+
+  void (*correct1)() = static_cast<void (*)()>(overloaded_function);
+  FnPtrVoid correct2 = static_cast<void (*)()>(&overloaded_function);
+  FnRefInt correct3 = static_cast<void (&)(int)>(overloaded_function);
+}
+
+struct S {
+    S(const char *);
+};
+struct ConvertibleToS {
+  operator S() const;
+};
+struct ConvertibleToSRef {
+  operator const S&() const;
+};
+
+void conversions() {
+  //auto s1 = (const S&)"";
+  auto s2 = (S)"";
+  auto s2a = (struct S)"";
+  auto s2b = (const S)"";
+  ConvertibleToS c;
+  auto s3 = (const S&)c;
+  auto s4 = (S)c;
+  ConvertibleToSRef cr;
+  auto s5 = (const S&)cr;
+  auto s6 = (S)cr;
+}