[clang-tidy]misc-const-correctness fix fake positive of function pointer

Author: Changqing-JING

clang-tools-extra/clang-tidy/misc/ConstCorrectnessCheck.cpp

@@ -249,7 +249,8 @@ void ConstCorrectnessCheck::check(const MatchFinder::MatchResult &Result) {
       CheckValue();
     if (WarnPointersAsPointers) {
       if (const auto *PT = dyn_cast<PointerType>(VT)) {
-        if (!PT->getPointeeType().isConstQualified())
+        if (!PT->getPointeeType().isConstQualified() &&
+            !PT->getPointeeType()->isFunctionType())
           CheckPointee();
       }
       if (const auto *AT = dyn_cast<ArrayType>(VT)) {

clang-tools-extra/docs/ReleaseNotes.rst

@@ -321,6 +321,10 @@ Changes in existing checks
 - Improved :doc:`misc-header-include-cycle
   <clang-tidy/checks/misc/header-include-cycle>` check performance.
 
+- Improved :doc:`misc-const-correctness
+  <clang-tidy/checks/misc/const-correctness>` check by fixing false positives
+  of function pointer.
+
 - Improved :doc:`modernize-avoid-c-arrays
   <clang-tidy/checks/modernize/avoid-c-arrays>` to not diagnose array types
   which are part of an implicit instantiation of a template.

clang-tools-extra/test/clang-tidy/checkers/misc/const-correctness-pointer-as-pointers.cpp

@@ -48,3 +48,7 @@ void ignore_const_alias() {
   p_local0 = &a[1];
 }
 
+void function_pointer_basic() {
+  void (*const fp)() = nullptr;
+  fp();
+}