[clang][ASTImporter] Fix crash when template class static member imported to other translation unit. (#68774)

Fixes: #68769

Co-authored-by: miaozhiyuan <[email protected]>

Author: mzyKi

clang/docs/ReleaseNotes.rst

@@ -670,6 +670,10 @@ Bug Fixes to C++ Support
   default initializing a base class in a constant expression context. Fixes:
   (`#69890 <https://github.com/llvm/llvm-project/issues/69890>`_)
 
+- Fix crash when template class static member imported to other translation unit.
+  Fixes:
+  (`#68769 <https://github.com/llvm/llvm-project/issues/68769>`_)
+
 Bug Fixes to AST Handling
 ^^^^^^^^^^^^^^^^^^^^^^^^^
 - Fixed an import failure of recursive friend class template.

clang/lib/AST/ASTImporter.cpp

@@ -4476,6 +4476,17 @@ ExpectedDecl ASTNodeImporter::VisitVarDecl(VarDecl *D) {
     auto ToVTOrErr = import(D->getDescribedVarTemplate());
     if (!ToVTOrErr)
       return ToVTOrErr.takeError();
+  } else if (MemberSpecializationInfo *MSI = D->getMemberSpecializationInfo()) {
+    TemplateSpecializationKind SK = MSI->getTemplateSpecializationKind();
+    VarDecl *FromInst = D->getInstantiatedFromStaticDataMember();
+    if (Expected<VarDecl *> ToInstOrErr = import(FromInst))
+      ToVar->setInstantiationOfStaticDataMember(*ToInstOrErr, SK);
+    else
+      return ToInstOrErr.takeError();
+    if (ExpectedSLoc POIOrErr = import(MSI->getPointOfInstantiation()))
+      ToVar->getMemberSpecializationInfo()->setPointOfInstantiation(*POIOrErr);
+    else
+      return POIOrErr.takeError();
   }
 
   if (Error Err = ImportInitializer(D, ToVar))

clang/unittests/AST/ASTImporterTest.cpp

@@ -1370,6 +1370,40 @@ TEST_P(ASTImporterOptionSpecificTestBase, ImportCorrectTemplatedDecl) {
   ASSERT_EQ(ToTemplated1, ToTemplated);
 }
 
+TEST_P(ASTImporterOptionSpecificTestBase,
+       ImportTemplateSpecializationStaticMember) {
+  auto FromCode =
+      R"(
+      template <typename H> class Test{
+      public:
+        static const unsigned int length;
+      };
+
+      template<> const unsigned int Test<int>::length;
+      template<> const unsigned int Test<int>::length = 0;
+      )";
+  auto ToCode =
+      R"(
+      template <typename H> class Test {
+      public:
+        static const unsigned int length;
+      };
+
+      template <> const unsigned int Test<int>::length;
+
+      void foo() { int i = 1 / Test<int>::length; }
+      )";
+  Decl *FromTU = getTuDecl(FromCode, Lang_CXX14);
+  auto FromDecl = FirstDeclMatcher<VarDecl>().match(
+      FromTU, varDecl(hasName("length"), isDefinition()));
+  Decl *ToTu = getToTuDecl(ToCode, Lang_CXX14);
+  auto ToX = Import(FromDecl, Lang_CXX03);
+  auto ToDecl = FirstDeclMatcher<VarDecl>().match(
+      ToTu, varDecl(hasName("length"), isDefinition()));
+  EXPECT_TRUE(ToX);
+  EXPECT_EQ(ToX, ToDecl);
+}
+
 TEST_P(ASTImporterOptionSpecificTestBase, ImportChooseExpr) {
   // This tests the import of isConditionTrue directly to make sure the importer
   // gets it right.