Make DiagnosticIDs::getAllDiagnostics static.

[leanil]

Summary

It doesn't depend on instance specific data, so this would make it easier to use, for example here:

[xazax.hun]

I like the idea of making functions that can be static, static. Could you update the usages of this function as well?

[leanil]

Update usages of the function.
Checked with clang-tidy readability-static-accessed-through-instance.

[xazax.hun]

LGTM!

include/clang/Basic/DiagnosticIDs.h

public:
   /// \brief Get the set of all diagnostic IDs in the group with the given name.
   ///
   /// \param[out] Diags - On return, the diagnostics in the group.
   /// \returns \c true if the given group is unknown, \c false otherwise.
   bool getDiagnosticsInGroup(diag::Flavor Flavor, StringRef Group,
                              SmallVectorImpl<diag::kind> &Diags) const;
 
   /// \brief Get the set of all diagnostic IDs.
-  void getAllDiagnostics(diag::Flavor Flavor,
-                         SmallVectorImpl<diag::kind> &Diags) const;
+  static void getAllDiagnostics(diag::Flavor Flavor,
+                                SmallVectorImpl<diag::kind> &Diags);
 
   /// \brief Get the diagnostic option with the closest edit distance to the
   /// given group name.
   static StringRef getNearestOption(diag::Flavor Flavor, StringRef Group);
 
 private:
   /// \brief Classify the specified diagnostic ID into a Level, consumable by
   /// the DiagnosticClient.

lib/Basic/DiagnosticIDs.cpp

auto Found = std::lower_bound(std::begin(OptionTable), std::end(OptionTable),
                                 });
   if (Found == std::end(OptionTable) || Found->getName() != Group)
     return true; // Option not found.
 
   return ::getDiagnosticsInGroup(Flavor, Found, Diags);
 }
 
 void DiagnosticIDs::getAllDiagnostics(diag::Flavor Flavor,
-                                     SmallVectorImpl<diag::kind> &Diags) const {
+                                      SmallVectorImpl<diag::kind> &Diags) {
   for (unsigned i = 0; i != StaticDiagInfoSize; ++i)
     if (StaticDiagInfo[i].getFlavor() == Flavor)
       Diags.push_back(StaticDiagInfo[i].DiagID);
 }
 
 StringRef DiagnosticIDs::getNearestOption(diag::Flavor Flavor,
                                           StringRef Group) {
   StringRef Best;