[cxx-interop] Check template argument safety in ClangDeclExplicitSafety

Checking this upon import was overlooking annotations that explicitly
mark a type as safe (or unsafe). Instead, we consolidate this logic in
the ClangDeclExplicitSafety request.

rdar://163196609

Author: j-hui

lib/ClangImporter/ClangImporter.cpp

@@ -8831,6 +8831,29 @@ ClangDeclExplicitSafety::evaluate(Evaluator &evaluator,
           ClangTypeEscapability({recordDecl->getTypeForDecl(), nullptr}),
           CxxEscapability::Unknown) != CxxEscapability::Unknown)
     return ExplicitSafety::Safe;
+
+  // A template class is unsafe if any of its type arguments are unsafe.
+  // Note that this does not rely on the record being defined.
+  if (const auto *ctsd =
+          dyn_cast<clang::ClassTemplateSpecializationDecl>(recordDecl)) {
+    for (auto arg : ctsd->getTemplateArgs().asArray()) {
+      switch (arg.getKind()) {
+      case clang::TemplateArgument::Type:
+        if (hasUnsafeType(evaluator, arg.getAsType()))
+          return ExplicitSafety::Unsafe;
+        break;
+      case clang::TemplateArgument::Pack:
+        for (auto pkArg : arg.getPackAsArray()) {
+          if (pkArg.getKind() == clang::TemplateArgument::Type &&
+              hasUnsafeType(evaluator, pkArg.getAsType()))
+            return ExplicitSafety::Unsafe;
+        }
+        break;
+      default:
+        continue;
+      }
+    }
+  }
 
   // If we don't have a definition, leave it unspecified.
   recordDecl = recordDecl->getDefinition();
@@ -8844,7 +8867,7 @@ ClangDeclExplicitSafety::evaluate(Evaluator &evaluator,
         return ExplicitSafety::Unsafe;
     }
   }
-  
+
   // Check the fields.
   for (auto field : recordDecl->fields()) {
     if (hasUnsafeType(evaluator, field->getType()))

lib/ClangImporter/ImportDecl.cpp

@@ -2300,40 +2300,6 @@ namespace {
         }
       }
 
-      if (const auto *ctsd =
-              dyn_cast<clang::ClassTemplateSpecializationDecl>(decl)) {
-        for (auto arg : ctsd->getTemplateArgs().asArray()) {
-          auto done = false;
-          auto checkUnsafe = [&](clang::TemplateArgument tyArg) {
-            if (tyArg.getKind() != clang::TemplateArgument::Type)
-              return;
-
-            auto safety =
-                evaluateOrDefault(Impl.SwiftContext.evaluator,
-                                  ClangTypeExplicitSafety({tyArg.getAsType()}),
-                                  ExplicitSafety::Unspecified);
-
-            if (safety == ExplicitSafety::Unsafe) {
-              result->addAttribute(new (Impl.SwiftContext)
-                                       UnsafeAttr(/*implicit=*/true));
-              done = true;
-            }
-          };
-
-          if (arg.getKind() == clang::TemplateArgument::Pack) {
-            for (auto pkArg : arg.getPackAsArray()) {
-              checkUnsafe(pkArg);
-              if (done)
-                break;
-            }
-          } else {
-            checkUnsafe(arg);
-          }
-          if (done)
-            break;
-        }
-      }
-
       bool isNonEscapable = false;
       if (evaluateOrDefault(
               Impl.SwiftContext.evaluator,

test/Interop/Cxx/class/safe-interop-mode.swift

@@ -94,6 +94,16 @@ using TTakePtr = TTake<int *>;
 using TTakeSafeTuple = TTake<SafeTuple>;
 using TTakeUnsafeTuple = TTake<UnsafeTuple>;
 
+// An escapability or explicit safety annotation means a type is considered safe
+// even if it would otherwise be considered unsafe.
+template <typename> struct SWIFT_ESCAPABLE TEscape {};
+template <typename> struct __attribute__((swift_attr("safe"))) TSafe { void *ptr; };
+
+using TEscapePtr = TEscape<int *>;
+using TEscapeUnsafeTuple = TEscape<UnsafeTuple>;
+using TSafePtr = TSafe<int *>;
+using TSafeTuple = TSafe<UnsafeTuple>;
+
 struct HoldsShared {
   SharedObject* obj;
 
@@ -212,3 +222,8 @@ func useTTakeUnsafeTuple(x: TTakeUnsafeTuple) {
   // expected-warning@+1{{expression uses unsafe constructs but is not marked with 'unsafe'}}
   _ = x // expected-note{{reference to parameter 'x' involves unsafe type}}
 }
+
+func useTEscapePtr(x: TEscapePtr) { _ = x }
+func useTEscapeUnsafeTuple(x: TEscapeUnsafeTuple) { _ = x }
+func useTSafePtr(x: TSafePtr) { _ = x }
+func useTSafeTuple(x: TSafeTuple) { _ = x }