[clang][ASTImporter] Fix import of VarDecl regarding thread local storage spec

[steakhal]

Summary

After the import, we did not copy the TSCSpec.
This commit resolves that.

[balazske]

Looks good, just find a better place for the test.

clang/unittests/AST/ASTImporterTest.cpp

817

The test can be moved to better place, probably after line 3481 and use ImportVariables. At least I want it not between two related tests, here between ImportUsingDecl and ImportUsingShadowDecl.

[steakhal]

Moved to line 3481, changed the test logic accordingly.

[balazske]

I did not notice that ImportVariables is different than ImportDecl, I like the first version of the test better (with ImportDecl) (but the current is not wrong), can you change it back only at a different position (line 738 can be good, before test "ImportRecordTypeInFunc")?

[steakhal]

Revert to the previous version and move to line 738 just before "ImportRecordTypeInFunc".

clang/lib/AST/ASTImporter.cpp

ExpectedDecl ASTNodeImporter::VisitVarDecl(VarDecl *D) {
   VarDecl *ToVar;
   if (GetImportedOrCreateDecl(ToVar, D, Importer.getToContext(), DC,
                               ToInnerLocStart, Loc,
                               Name.getAsIdentifierInfo(),
                               ToType, ToTypeSourceInfo,
                               D->getStorageClass()))
     return ToVar;
 
+  ToVar->setTSCSpec(D->getTSCSpec());
   ToVar->setQualifierInfo(ToQualifierLoc);
   ToVar->setAccess(D->getAccess());
   ToVar->setLexicalDeclContext(LexicalDC);
 
   if (FoundByLookup) {
     auto *Recent = const_cast<VarDecl *>(FoundByLookup->getMostRecentDecl());
     ToVar->setPreviousDecl(Recent);
   }

clang/unittests/AST/ASTImporterTest.cpp

 TEST_P(ImportDecl, ImportUsingDecl) {
   MatchVerifier<Decl> Verifier;
   testImport("namespace foo { int bar; }"
              "void declToImport() { using foo::bar; }",
              Lang_CXX03, "", Lang_CXX03, Verifier,
              functionDecl(hasDescendant(usingDecl())));
 }
 
 /// \brief Matches shadow declarations introduced into a scope by a
 ///        (resolved) using declaration.
 ///
 /// Given
 /// \code
 ///   namespace n { int f; }
 ///   namespace declToImport { using n::f; }
 /// \endcode
 /// usingShadowDecl()
TEST_P(ASTImporterOptionSpecificTestBase,
   EXPECT_TRUE(ToD);
   auto *ToInitExpr = cast<VarDecl>(ToD)->getAnyInitializer();
   EXPECT_TRUE(ToInitExpr);
   EXPECT_TRUE(ToInitExpr->isGLValue());
 }
 
 struct ImportVariables : ASTImporterOptionSpecificTestBase {};
 
+TEST_P(ImportVariables, ImportedVarDeclPreservesThreadLocalStorage) {
+  Decl *FromTU =
+      getTuDecl("thread_local int declToImport;", Lang_CXX11, "input1.cc");
+
+  auto *FromDWithTLS = FirstDeclMatcher<VarDecl>().match(
+      FromTU, varDecl(hasThreadStorageDuration()));
+  ASSERT_TRUE(FromDWithTLS);
+  ASSERT_EQ(SD_Thread, FromDWithTLS->getStorageDuration());
+
+  const auto *ToD = Import(FromDWithTLS, Lang_CXX11);
+  ASSERT_TRUE(ToD);
+  EXPECT_EQ(SD_Thread, ToD->getStorageDuration());
+}
+
 TEST_P(ImportVariables, ImportOfOneDeclBringsInTheWholeChain) {
   Decl *FromTU = getTuDecl(
       R"(
       struct A {
         static const int a = 1 + 2;
       };
       const int A::a;
       )",