[clang-tidy] bug fix: Don't warn on partial template specialization in `misc-definitions-in-headers` check.

[alexfh]

LG. Do you need me to commit the patch?

[hokein]

Yes, please help to land the patch for me :). Thanks.

[hokein]

@alexfh, I get commit access, and have committed the patch by myself (Seems it is a successful commit :D ).

clang-tidy/misc/DefinitionsInHeadersCheck.cpp

if (const auto *FD = dyn_cast<FunctionDecl>(ND)) {
     // Function template full specialization is prohibited in header file.
     if (FD->getTemplateSpecializationKind() == TSK_ImplicitInstantiation)
       return;
     // Member function of a class template and member function of a nested class
     // in a class template are allowed.
     if (const auto *MD = dyn_cast<CXXMethodDecl>(FD)) {
       const auto *DC = MD->getDeclContext();
       while (DC->isRecord()) {
-        if (const auto *RD = dyn_cast<CXXRecordDecl>(DC))
+        if (const auto *RD = dyn_cast<CXXRecordDecl>(DC)) {
+          if (isa<ClassTemplatePartialSpecializationDecl>(RD))
+            return;
           if (RD->getDescribedClassTemplate())
             return;
+        }
         DC = DC->getParent();
       }
     }
 
     diag(FD->getLocation(),
          "function '%0' defined in a header file; "
          "function definitions in header files can lead to ODR violations")
         << FD->getNameInfo().getName().getAsString()

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

namespace {
   int e = 2;
 // CHECK-MESSAGES: :[[@LINE-1]]:7: warning: variable 'e' defined in a header file;
 }
 
 const char* const g = "foo"; // OK: internal linkage variable definition.
 static int h = 1; // OK: internal linkage variable definition.
 const int i = 1; // OK: internal linkage variable definition.
 extern int j; // OK: internal linkage variable definition.
+
+template <typename T, typename U>
+struct CD {
+  int f();
+};
+
+template <typename T>
+struct CD<T, int> {
+  int f();
+};
+
+template <>
+struct CD<int, int> {
+  int f();
+};
+
+int CD<int, int>::f() {
+// CHECK-MESSAGES: :[[@LINE-1]]:19: warning: function 'f' defined in a header file;
+  return 0;
+}
+
+template <typename T>
+int CD<T, int>::f() { // OK: partial template specialization.
+  return 0;
+}