[clang-rename] Fix rename on function template specializations.

[hokein]

Summary

previously, we missed to rename occurrences to explicit function template
specilizations.

[hokein]

update

[hokein]

@kbobyrev you may miss this patch, this is a separate patch from D89300.

[kbobyrev]

And indeed I did miss that :( Thank you!

clang/lib/Tooling/Refactoring/Rename/USRFindingAction.cpp

if (const auto *MethodDecl = dyn_cast<CXXMethodDecl>(FoundDecl)) {
           USRSet.insert(getUSRForDecl(OverriddenMethod));
       }
       addUSRsOfInstantiatedMethods(MethodDecl);
     } else if (const auto *RecordDecl = dyn_cast<CXXRecordDecl>(FoundDecl)) {
       handleCXXRecordDecl(RecordDecl);
     } else if (const auto *TemplateDecl =
                    dyn_cast<ClassTemplateDecl>(FoundDecl)) {
       handleClassTemplateDecl(TemplateDecl);
+    } else if (const auto *FD = dyn_cast<FunctionDecl>(FoundDecl)) {
+      USRSet.insert(getUSRForDecl(FD));
+      if (const auto *FTD = FD->getPrimaryTemplate())
+        handleFunctionTemplateDecl(FTD);
+    } else if (const auto *FD = dyn_cast<FunctionTemplateDecl>(FoundDecl)) {
+      handleFunctionTemplateDecl(FD);
     } else {
       USRSet.insert(getUSRForDecl(FoundDecl));
     }
     return std::vector<std::string>(USRSet.begin(), USRSet.end());
   }
 
   bool shouldVisitTemplateInstantiations() const { return true; }
 
for (const auto *Specialization : TemplateDecl->specializations())
       addUSRsOfCtorDtors(Specialization);
     SmallVector<ClassTemplatePartialSpecializationDecl *, 4> PartialSpecs;
     TemplateDecl->getPartialSpecializations(PartialSpecs);
     for (const auto *Spec : PartialSpecs)
       addUSRsOfCtorDtors(Spec);
     addUSRsOfCtorDtors(TemplateDecl->getTemplatedDecl());
   }
 
+  void handleFunctionTemplateDecl(const FunctionTemplateDecl *FTD) {
+    USRSet.insert(getUSRForDecl(FTD));
+    USRSet.insert(getUSRForDecl(FTD->getTemplatedDecl()));
+    for (const auto *S : FTD->specializations())
+      USRSet.insert(getUSRForDecl(S));
+  }
+
   void addUSRsOfCtorDtors(const CXXRecordDecl *RD) {
     const auto* RecordDecl = RD->getDefinition();
 
     // Skip if the CXXRecordDecl doesn't have definition.
     if (!RecordDecl) {
       USRSet.insert(getUSRForDecl(RD));
       return;
     }

clang/test/clang-rename/FunctionTemplate.cpp

+template <typename T>
+void Foo(T t); // CHECK: void Bar(T t);
+
+template <>
+void Foo(int a); // CHECK: void Bar(int a);
+
+void test() {
+  Foo<double>(1); // CHECK: Bar<double>(1);
+}
+
+// Test 1.
+// RUN: clang-rename -offset=28 -new-name=Bar %s -- | sed 's,//.*,,' | FileCheck %s
+// Test 2.
+// RUN: clang-rename -offset=81 -new-name=Bar %s -- | sed 's,//.*,,' | FileCheck %s
+// Test 3.
+// RUN: clang-rename -offset=137 -new-name=Bar %s -- | sed 's,//.*,,' | FileCheck %s
+
+// To find offsets after modifying the file, use:
+//   grep -Ubo 'Foo.*' <file>