[clang] [clang][ASTImporter] Improve import of variable template specializations. (PR #78284)

[Shafik Yaghmour via cfe-commits]

=?utf-8?q?Balázs_Kéri?= <balazs.keri at ericsson.com>
Message-ID:
In-Reply-To: <llvm.org/llvm/llvm-project/pull/78284 at github.com>


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@@ -6397,116 +6400,132 @@ ExpectedDecl ASTNodeImporter::VisitVarTemplateSpecializationDecl(
 
   // Try to find an existing specialization with these template arguments.
   void *InsertPos = nullptr;
-  VarTemplateSpecializationDecl *D2 = VarTemplate->findSpecialization(
-      TemplateArgs, InsertPos);
-  if (D2) {
-    // We already have a variable template specialization with these template
-    // arguments.
-
-    // FIXME: Check for specialization vs. instantiation errors.
-
-    if (VarDecl *FoundDef = D2->getDefinition()) {
-      if (!D->isThisDeclarationADefinition() ||
-          IsStructuralMatch(D, FoundDef)) {
-        // The record types structurally match, or the "from" translation
-        // unit only had a forward declaration anyway; call it the same
-        // variable.
-        return Importer.MapImported(D, FoundDef);
+  VarTemplateSpecializationDecl *FoundSpecialization =
+      VarTemplate->findSpecialization(TemplateArgs, InsertPos);
+  if (FoundSpecialization) {
+    if (IsStructuralMatch(D, FoundSpecialization)) {
+      VarDecl *FoundDef = FoundSpecialization->getDefinition();
+      if (D->getDeclContext()->isRecord()) {
+        // In a record, it is allowed only to have one optional declaration and
+        // one definition of the (static or constexpr) variable template.
+        assert(
+            FoundSpecialization->getDeclContext()->isRecord() &&
+            "Member variable template specialization imported as non-member, "
+            "inconsistent imported AST?");
+        if (FoundDef)
+          return Importer.MapImported(D, FoundDef);
+        if (!D->isThisDeclarationADefinition())
+          return Importer.MapImported(D, FoundSpecialization);
+      } else {
+        // If definition is imported and there is already one, map to it.
+        // Otherwise create a new variable and link it to the existing.
+        if (FoundDef && D->isThisDeclarationADefinition())
+          return Importer.MapImported(D, FoundDef);
       }
+    } else {
+      return make_error<ASTImportError>(ASTImportError::NameConflict);
     }
-  } else {
-    TemplateArgumentListInfo ToTAInfo;
-    if (const ASTTemplateArgumentListInfo *Args = D->getTemplateArgsInfo()) {
-      if (Error Err = ImportTemplateArgumentListInfo(*Args, ToTAInfo))
-        return std::move(Err);
-    }
+  }
 
-    using PartVarSpecDecl = VarTemplatePartialSpecializationDecl;
-    // Create a new specialization.
-    if (auto *FromPartial = dyn_cast<PartVarSpecDecl>(D)) {
-      // Import TemplateArgumentListInfo
-      TemplateArgumentListInfo ArgInfos;
-      const auto *FromTAArgsAsWritten = FromPartial->getTemplateArgsAsWritten();
-      // NOTE: FromTAArgsAsWritten and template parameter list are non-null.
-      if (Error Err = ImportTemplateArgumentListInfo(
-          *FromTAArgsAsWritten, ArgInfos))
-        return std::move(Err);
+  VarTemplateSpecializationDecl *D2 = nullptr;
 
-      auto ToTPListOrErr = import(FromPartial->getTemplateParameters());
-      if (!ToTPListOrErr)
-        return ToTPListOrErr.takeError();
+  TemplateArgumentListInfo ToTAInfo;
+  if (const ASTTemplateArgumentListInfo *Args = D->getTemplateArgsInfo()) {
+    if (Error Err = ImportTemplateArgumentListInfo(*Args, ToTAInfo))
+      return std::move(Err);
+  }
 
-      PartVarSpecDecl *ToPartial;
-      if (GetImportedOrCreateDecl(ToPartial, D, Importer.getToContext(), DC,
-                                  *BeginLocOrErr, *IdLocOrErr, *ToTPListOrErr,
-                                  VarTemplate, QualType(), nullptr,
-                                  D->getStorageClass(), TemplateArgs, ArgInfos))
-        return ToPartial;
+  using PartVarSpecDecl = VarTemplatePartialSpecializationDecl;
+  // Create a new specialization.
+  if (auto *FromPartial = dyn_cast<PartVarSpecDecl>(D)) {
+    // Import TemplateArgumentListInfo
+    TemplateArgumentListInfo ArgInfos;
+    const auto *FromTAArgsAsWritten = FromPartial->getTemplateArgsAsWritten();
+    // NOTE: FromTAArgsAsWritten and template parameter list are non-null.
+    if (Error Err =
+            ImportTemplateArgumentListInfo(*FromTAArgsAsWritten, ArgInfos))
+      return std::move(Err);
 
-      if (Expected<PartVarSpecDecl *> ToInstOrErr = import(
-          FromPartial->getInstantiatedFromMember()))
-        ToPartial->setInstantiatedFromMember(*ToInstOrErr);
-      else
-        return ToInstOrErr.takeError();
-
-      if (FromPartial->isMemberSpecialization())
-        ToPartial->setMemberSpecialization();
-
-      D2 = ToPartial;
-
-      // FIXME: Use this update if VarTemplatePartialSpecializationDecl is fixed
-      // to adopt template parameters.
-      // updateLookupTableForTemplateParameters(**ToTPListOrErr);
-    } else { // Full specialization
-      if (GetImportedOrCreateDecl(D2, D, Importer.getToContext(), DC,
-                                  *BeginLocOrErr, *IdLocOrErr, VarTemplate,
-                                  QualType(), nullptr, D->getStorageClass(),
-                                  TemplateArgs))
-        return D2;
-    }
+    auto ToTPListOrErr = import(FromPartial->getTemplateParameters());
+    if (!ToTPListOrErr)
+      return ToTPListOrErr.takeError();
 
-    QualType T;
-    if (Error Err = importInto(T, D->getType()))
-      return std::move(Err);
-    D2->setType(T);
+    PartVarSpecDecl *ToPartial;
+    if (GetImportedOrCreateDecl(ToPartial, D, Importer.getToContext(), DC,
+                                *BeginLocOrErr, *IdLocOrErr, *ToTPListOrErr,
+                                VarTemplate, QualType(), nullptr,
----------------
shafik wrote:

`nullptr` -> `/*TInfo=*/nullptr` 

I think `TInfo` is the right field here.

https://github.com/llvm/llvm-project/pull/78284