[clang-tidy] Improve google-objc-function-naming diagnostics 📙

Summary:
The diagnostics from google-objc-function-naming check will be more
actionable if they provide a brief description of the requirements from
the Google Objective-C style guide. The more descriptive diagnostics may
help clarify that functions in the global namespace must have an
appropriate prefix followed by Pascal case (engineers working previously
with static functions might not immediately understand the different
requirements of static and non-static functions).

Test Notes:
Verified against the clang-tidy tests.

Reviewers: benhamilton, aaron.ballman

Reviewed By: benhamilton

Subscribers: MyDeveloperDay, xazax.hun, cfe-commits

Differential Revision: https://reviews.llvm.org/D55482

llvm-svn: 349123

1 files changed, 5 insertions, 3 deletions

diff --git a/clang-tools-extra/clang-tidy/google/FunctionNamingCheck.cpp b/clang-tools-extra/clang-tidy/google/FunctionNamingCheck.cpp
index 6d07472ef54..f7064708d4b 100644
--- a/clang-tools-extra/clang-tidy/google/FunctionNamingCheck.cpp
+++ b/clang-tools-extra/clang-tidy/google/FunctionNamingCheck.cpp
@@ -110,10 +110,12 @@ void FunctionNamingCheck::registerMatchers(MatchFinder *Finder) {
 void FunctionNamingCheck::check(const MatchFinder::MatchResult &Result) {
   const auto *MatchedDecl = Result.Nodes.getNodeAs<FunctionDecl>("function");
 
+  bool IsGlobal = MatchedDecl->getStorageClass() != SC_Static;
   diag(MatchedDecl->getLocation(),
-       "function name %0 not using function naming conventions described by "
-       "Google Objective-C style guide")
-      << MatchedDecl << generateFixItHint(MatchedDecl);
+       "%select{static function|function in global namespace}1 named %0 must "
+       "%select{be in|have an appropriate prefix followed by}1 Pascal case as "
+       "required by Google Objective-C style guide")
+      << MatchedDecl << IsGlobal << generateFixItHint(MatchedDecl);
 }
 
 } // namespace objc