Add flag to specify an alternative to std::forward

Since std::forward is nothing more than a cast, part of STL and not the
language itself, it's easy to provide a custom implementation if one
wishes not to include the entirety of <utility>.

Added flag (ForwardFunction) provides a way to continue using this
essential check even with the custom implementation of forwarding.

Author: DimitrijeDobrota

clang-tools-extra/clang-tidy/cppcoreguidelines/MissingStdForwardCheck.cpp

@@ -120,7 +120,7 @@ void MissingStdForwardCheck::registerMatchers(MatchFinder *Finder) {
                           equalsBoundNode("param"), equalsBoundNode("var")))))),
                 CapturedInLambda)),
       callee(unresolvedLookupExpr(hasAnyDeclaration(
-          namedDecl(hasUnderlyingDecl(hasName("::std::forward")))))),
+          namedDecl(hasUnderlyingDecl(hasName(ForwardFunction)))))),
 
       unless(anyOf(hasAncestor(typeLoc()),
                    hasAncestor(expr(hasUnevaluatedContext())))));
@@ -149,4 +149,13 @@ void MissingStdForwardCheck::check(const MatchFinder::MatchResult &Result) {
       << Param;
 }
 
+MissingStdForwardCheck::MissingStdForwardCheck(StringRef Name,
+                                               ClangTidyContext *Context)
+    : ClangTidyCheck(Name, Context),
+      ForwardFunction(Options.get("ForwardFunction", "::std::forward")) {}
+
+void MissingStdForwardCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
+  Options.store(Opts, "ForwardFunction", ForwardFunction);
+}
+
 } // namespace clang::tidy::cppcoreguidelines

clang-tools-extra/clang-tidy/cppcoreguidelines/MissingStdForwardCheck.h

@@ -21,8 +21,7 @@ namespace clang::tidy::cppcoreguidelines {
 /// http://clang.llvm.org/extra/clang-tidy/checks/cppcoreguidelines/missing-std-forward.html
 class MissingStdForwardCheck : public ClangTidyCheck {
 public:
-  MissingStdForwardCheck(StringRef Name, ClangTidyContext *Context)
-      : ClangTidyCheck(Name, Context) {}
+  MissingStdForwardCheck(StringRef Name, ClangTidyContext *Context);
   void registerMatchers(ast_matchers::MatchFinder *Finder) override;
   void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
   bool isLanguageVersionSupported(const LangOptions &LangOpts) const override {
@@ -31,6 +30,10 @@ class MissingStdForwardCheck : public ClangTidyCheck {
   std::optional<TraversalKind> getCheckTraversalKind() const override {
     return TK_IgnoreUnlessSpelledInSource;
   }
+  void storeOptions(ClangTidyOptions::OptionMap &Opts) override;
+
+private:
+  const StringRef ForwardFunction;
 };
 
 } // namespace clang::tidy::cppcoreguidelines

clang-tools-extra/docs/ReleaseNotes.rst

@@ -327,6 +327,10 @@ Changes in existing checks
   <clang-tidy/checks/readability/redundant-smartptr-get>` check by fixing
   some false positives involving smart pointers to arrays.
 
+- Improved :doc:`cppcoreguidelines-missing-std-forward
+  <clang-tidy/checks/cppcoreguidelines/missing-std-forward>` check by adding a
+  flag to specify the function used for forwarding instead of ``std::forward``.
+
 Removed checks
 ^^^^^^^^^^^^^^
 

clang-tools-extra/docs/clang-tidy/checks/cppcoreguidelines/missing-std-forward.rst

@@ -35,6 +35,14 @@ Example:
     f(1, 2); // Incorrect - may not invoke the desired qualified function operator
   }
 
+Options
+-------
+
+.. option:: ForwardFunction
+
+   Specify the function used for forwarding.
+   Default is `::std::forward`.
+
 This check implements `F.19
 <http://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines#Rf-forward>`_
 from the C++ Core Guidelines.