Revert "[cxx-interop] Do not import template type arguments"

This reverts commit d5473fe.

Author: j-hui

lib/ClangImporter/ImportDecl.cpp

@@ -2301,6 +2301,34 @@ namespace {
         }
       }
 
+      // We have to do this after populating ImportedDecls to avoid importing
+      // the same decl multiple times. Also after we imported the bases.
+      if (const auto *ctsd =
+              dyn_cast<clang::ClassTemplateSpecializationDecl>(decl)) {
+        for (auto arg : ctsd->getTemplateArgs().asArray()) {
+          llvm::SmallVector<clang::TemplateArgument, 1> nonPackArgs;
+          if (arg.getKind() == clang::TemplateArgument::Pack) {
+            auto pack = arg.getPackAsArray();
+            nonPackArgs.assign(pack.begin(), pack.end());
+          } else {
+            nonPackArgs.push_back(arg);
+          }
+          for (auto realArg : nonPackArgs) {
+            if (realArg.getKind() != clang::TemplateArgument::Type)
+              continue;
+            auto SwiftType = Impl.importTypeIgnoreIUO(
+                realArg.getAsType(), ImportTypeKind::Abstract,
+                [](Diagnostic &&diag) {}, false, Bridgeability::None,
+                ImportTypeAttrs());
+            if (SwiftType && SwiftType->isUnsafe()) {
+              auto attr = new (Impl.SwiftContext) UnsafeAttr(/*implicit=*/true);
+              result->getAttrs().add(attr);
+              break;
+            }
+          }
+        }
+      }
+
       bool isNonEscapable = false;
       if (evaluateOrDefault(
               Impl.SwiftContext.evaluator,