[clang-tidy] Provide fix-its for downcasts in google-readability-casting

Author: ckandeler

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

@@ -269,6 +269,12 @@ void AvoidCStyleCastsCheck::check(const MatchFinder::MatchResult &Result) {
  return;
  }
  break;
+ case CK_BaseToDerived:
+ if (!needsConstCast(SourceType, DestType)) {
+ ReplaceWithNamedCast("static_cast");
+ return;
+ }
+ break;
  default:
  break;
  }

clang-tools-extra/docs/ReleaseNotes.rst

@@ -334,6 +334,10 @@ Changes in existing checks
  adding an option to allow pointer arithmetic via prefix/postfix increment or
  decrement operators.
 
+- Improved :doc:`google-readability-casting
+ <clang-tidy/checks/google/readability-casting>` check by adding a fix-it
+ for downcasts.
+
 - Improved :doc:`llvm-prefer-isa-or-dyn-cast-in-conditionals
  <clang-tidy/checks/llvm/prefer-isa-or-dyn-cast-in-conditionals>` check:
 

clang-tools-extra/test/clang-tidy/checkers/google/readability-casting.cpp

@@ -102,9 +102,11 @@ void f(int a, double b, const char *cpc, const void *cpv, X *pX) {
  // CHECK-FIXES: b1 = static_cast<int>(b);
 
  Y *pB = (Y*)pX;
- // CHECK-MESSAGES: :[[@LINE-1]]:11: warning: {{.*}}; use static_cast/const_cast/reinterpret_cast [
+ // CHECK-MESSAGES: :[[@LINE-1]]:11: warning: {{.*}}; use static_cast {{.*}}
+ // CHECK-FIXES: Y *pB = static_cast<Y*>(pX);
  Y &rB = (Y&)*pX;
- // CHECK-MESSAGES: :[[@LINE-1]]:11: warning: {{.*}}; use static_cast/const_cast/reinterpret_cast [
+ // CHECK-MESSAGES: :[[@LINE-1]]:11: warning: {{.*}}; use static_cast {{.*}}
+ // CHECK-FIXES: Y &rB = static_cast<Y&>(*pX);
 
  const char *pc3 = (const char*)cpv;
  // CHECK-MESSAGES: :[[@LINE-1]]:21: warning: {{.*}}; use static_cast [