Don’t add HasStorageAttr to ABI-only decls

It’s unnecessary, shouldn’t be serialized into module interfaces, and Swift doesn’t know how to compute it for an ABI-only decl since it doesn’t have accessors or an initial value.

No tests because enforcement isn’t in yet.

Author: beccadax

lib/Sema/TypeCheckStorage.cpp

@@ -3733,6 +3733,11 @@ static StorageImplInfo classifyWithHasStorageAttr(VarDecl *var) {
 
 bool HasStorageRequest::evaluate(Evaluator &evaluator,
                                  AbstractStorageDecl *storage) const {
+  // ABI decl inherits this from API.
+  auto abiRole = ABIRoleInfo(storage);
+  if (!abiRole.providesAPI() && abiRole.getCounterpart())
+    return abiRole.getCounterpart()->hasStorage();
+
   // Parameters are always stored.
   if (isa<ParamDecl>(storage))
     return true;
@@ -3818,7 +3823,11 @@ void HasStorageRequest::cacheResult(bool hasStorage) const {
     return;
 
   if (auto varDecl = dyn_cast<VarDecl>(decl)) {
-    if (hasStorage && !varDecl->getAttrs().hasAttribute<HasStorageAttr>())
+    auto abiRole = ABIRoleInfo(varDecl);
+    bool abiOnly = !abiRole.providesAPI() && abiRole.getCounterpart();
+
+    if (hasStorage && !abiOnly &&
+          !varDecl->getAttrs().hasAttribute<HasStorageAttr>())
       varDecl->getAttrs().add(new (varDecl->getASTContext())
                               HasStorageAttr(/*isImplicit=*/true));
   }

lib/Serialization/Deserialization.cpp

@@ -4025,7 +4025,8 @@ class DeclDeserializer {
       AddAttribute(new (ctx) OverrideAttr(SourceLoc()));
 
     // Add the @_hasStorage attribute if this var has storage.
-    if (var->hasStorage())
+    // (Unless it's an ABI-only decl--they shouldn't have a HasStorageAttr.)
+    if (var->hasStorage() && ABIDeclCounterpartID == 0)
       AddAttribute(new (ctx) HasStorageAttr(/*isImplicit:*/true));
 
     {