[clang-tidy] Fix description for misc-definitions-in-headers.

[gribozavr]

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

133

"mark as inline"?

IDK, "make inline" does not read right to me.

[hokein]

Address comment.

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

if (const auto *MD = dyn_cast<CXXMethodDecl>(FD)) {
             return;
           if (RD->getDescribedClassTemplate())
             return;
         }
         DC = DC->getParent();
       }
     }
 
-    bool is_full_spec = FD->getTemplateSpecializationKind() != TSK_Undeclared;
+    bool IsFullSpec = FD->getTemplateSpecializationKind() != TSK_Undeclared;
     diag(FD->getLocation(),
          "%select{function|full function template specialization}0 %1 defined "
          "in a header file; function definitions in header files can lead to "
          "ODR violations")
-        << is_full_spec << FD << FixItHint::CreateInsertion(
-                     FD->getReturnTypeSourceRange().getBegin(), "inline ");
+        << IsFullSpec << FD;
+    diag(FD->getLocation(), /*FixDescription=*/"make 'inline'",
+         DiagnosticIDs::Note)
+        << FixItHint::CreateInsertion(FD->getReturnTypeSourceRange().getBegin(),
+                                      "inline ");
   } else if (const auto *VD = dyn_cast<VarDecl>(ND)) {
     // Static data members of a class template are allowed.
     if (VD->getDeclContext()->isDependentContext() && VD->isStaticDataMember())
       return;
     // Ignore instantiated static data members of classes.
     if (isTemplateInstantiation(VD->getTemplateSpecializationKind()))
       return;
     // Ignore variable definition within function scope.

clang-tools-extra/test/clang-tidy/misc-definitions-in-headers.hpp

 // RUN: %check_clang_tidy %s misc-definitions-in-headers %t
 
 int f() {
 // CHECK-MESSAGES: :[[@LINE-1]]:5: warning: function 'f' defined in a header file; function definitions in header files can lead to ODR violations [misc-definitions-in-headers]
+// CHECK-MESSAGES: :[[@LINE-2]]:5: note: make 'inline'
 // CHECK-FIXES: inline int f() {
   return 1;
 }
 
 class CA {
   void f1() {} // OK: inline class member function definition.
   void f2();
   template<typename T>