[clang-tidy] Move the missing namespace comment warnings to the closing brace

[alexfh]

Summary

The google-readability-namespace-comments/llvm-namespace-comment
warnings are quite confusing when they appear at the beginning of a long
namespace and the closing brace is not in sight.

For convenience added notes pointing to the start of the namespace.

[alexfh]

Ping.

[klimek]

Lg

clang-tidy/readability/NamespaceCommentCheck.cpp

if (Tok.is(tok::comment) && NextTokenIsOnSameLine) {
 
     // This is not a recognized form of a namespace closing comment.
     // Leave line comment on the same line. Move block comment to the next line,
     // as it can be multi-line or there may be other tokens behind it.
     if (Comment.startswith("//"))
       NeedLineBreak = false;
   }
 
-  diag(ND->getLocation(), "namespace not terminated with a closing comment")
+  std::string NamespaceName =
+      ND->isAnonymousNamespace()
+          ? "anonymous namespace"
+          : ("namespace '" + ND->getNameAsString() + "'");
+
+  diag(AfterRBrace, "%0 not terminated with a closing comment")
+      << NamespaceName
       << FixItHint::CreateInsertion(AfterRBrace,
                                     std::string(SpacesBeforeComments, ' ') +
                                         getNamespaceComment(ND, NeedLineBreak));
+  diag(ND->getLocation(), "%0 starts here", DiagnosticIDs::Note)
+      << NamespaceName;
 }
 
 } // namespace readability
 } // namespace tidy
 } // namespace clang

test/clang-tidy/basic.cpp

 // RUN: clang-tidy %s -checks='-*,llvm-namespace-comment' -- | FileCheck %s
 
 namespace i {
 }
-// CHECK: warning: namespace not terminated with a closing comment [llvm-namespace-comment]
+// CHECK: warning: namespace 'i' not terminated with a closing comment [llvm-namespace-comment]

test/clang-tidy/google-readability-namespace-comments.cpp

 // RUN: $(dirname %s)/check_clang_tidy.sh %s google-readability-namespace-comments %t
 // REQUIRES: shell
 
-// CHECK-MESSAGES: :[[@LINE+2]]:11: warning: namespace not terminated with a closing comment [google-readability-namespace-comments]
-// CHECK-MESSAGES: :[[@LINE+2]]:11: warning: namespace not terminated with a closing comment [google-readability-namespace-comments]
 namespace n1 {
 namespace n2 {
-
+// CHECK-MESSAGES: :[[@LINE+4]]:2: warning: namespace 'n2' not terminated with a closing comment [google-readability-namespace-comments]
+// CHECK-MESSAGES: :[[@LINE-2]]:11: note: namespace 'n2' starts here
+// CHECK-MESSAGES: :[[@LINE+3]]:2: warning: namespace 'n1' not terminated with
+// CHECK-MESSAGES: :[[@LINE-5]]:11: note: namespace 'n1' starts here
 }
 }
 // CHECK-FIXES: }  // namespace n2
 // CHECK-FIXES: }  // namespace n1
 
 
 namespace short1 { namespace short2 { } }

test/clang-tidy/select-checks.cpp

 // RUN: clang-tidy %s -checks='-*,llvm-namespace-*' -- 2>&1 | FileCheck -implicit-check-not='{{warning:|error:}}' %s
 // RUN: clang-tidy %s -checks='-*,an-unknown-check' -- 2>&1 | FileCheck -implicit-check-not='{{warning:|error:}}' -check-prefix=CHECK2 %s
 
 // CHECK2: Error: no checks enabled.
 
 namespace i {
 }
-// CHECK: :[[@LINE-2]]:11: warning: namespace not terminated with a closing comment [llvm-namespace-comment]
+// CHECK: :[[@LINE-1]]:2: warning: namespace 'i' not terminated with a closing comment [llvm-namespace-comment]
 
 // Expect no warnings from the google-explicit-constructor check:
 class A { A(int i); };