[clang-tidy] Add fix-it for C-style cast of nullptr

clang-tools-extra/clang-tidy/modernize/AvoidCStyleCastCheck.cpp

@@ -218,6 +218,11 @@ void AvoidCStyleCastCheck::check(const MatchFinder::MatchResult &Result) {
       ReplaceWithNamedCast("static_cast");
     return;
   case CK_NoOp:
+  if (isa<CXXNullPtrLiteralExpr>(CastExpr->getSubExprAsWritten()->IgnoreImpCasts())) {
+  ReplaceWithNamedCast("static_cast");
+  return;
+}
+
     if (FnToFnCast) {
       ReplaceWithNamedCast("static_cast");
       return;

clang-tools-extra/docs/ReleaseNotes.rst

@@ -544,6 +544,10 @@ Changes in existing checks
   on Windows when the check was enabled with a 32-bit :program:`clang-tidy`
   binary.
 
+- Improved :doc:`modernize-avoid-c-style-cast  
+  <clang-tidy/checks/modernize/avoid-c-style-cast>` by providing correct fixes 
+  for C-style casts of nullptr.
+
 - Improved :doc:`modernize-use-override
   <clang-tidy/checks/modernize/use-override>` by fixing an issue where
   the check would sometimes suggest inserting ``override`` in an invalid

clang-tools-extra/test/clang-tidy/checkers/modernize/avoid-c-style-cast.cpp

@@ -368,3 +368,12 @@ void functional_casts() {
 
   throw S2(5.0f);
 }
+void f(int *);
+void f(double *);
+
+void test_nullptr_cast() {
+  f((int*)nullptr);
+}
+// CHECK-MESSAGES: warning: C-style casts are discouraged
+// CHECK-FIXES: f(static_cast<int*>(nullptr));
+