[PATCH] D65269: [ASTImporter] Fix for import of friend class template with definition.

[Balázs Kéri via Phabricator via cfe-commits]

balazske created this revision.
Herald added subscribers: cfe-commits, gamesh411, Szelethus, dkrupp.
Herald added a reviewer: martong.
Herald added a reviewer: a.sidorin.
Herald added a reviewer: shafik.
Herald added a project: clang.

If there is a friend class template "prototype" (forward declaration)
and later a definition for it in the existing code, this existing
definition may be not found by ASTImporter because it is not linked
to the prototype (under the friend AST node). The problem is fixed by
looping over all found matching decls instead of break after the first
found one.


Repository:
  rC Clang

https://reviews.llvm.org/D65269

Files:
  lib/AST/ASTImporter.cpp
  unittests/AST/ASTImporterTest.cpp


Index: unittests/AST/ASTImporterTest.cpp
===================================================================
--- unittests/AST/ASTImporterTest.cpp
+++ unittests/AST/ASTImporterTest.cpp
@@ -5138,6 +5138,50 @@
   EXPECT_TRUE(ToF);
 }
 
+TEST_P(ASTImporterOptionSpecificTestBase,
+       ImportExistingFriendClassTemplateDef) {
+  auto Code =
+      R"(
+        template <class T1, class T2>
+        struct Base {
+          template <class U1, class U2>
+          friend struct Class;
+        };
+        template <class T1, class T2>
+        struct Class { };
+        )";
+
+  TranslationUnitDecl *ToTU = getToTuDecl(Code, Lang_CXX);
+  TranslationUnitDecl *FromTU = getTuDecl(Code, Lang_CXX, "input.cc");
+
+  auto *ToClassProto = FirstDeclMatcher<ClassTemplateDecl>().match(
+      ToTU, classTemplateDecl(hasName("Class")));
+  auto *ToClassDef = LastDeclMatcher<ClassTemplateDecl>().match(
+      ToTU, classTemplateDecl(hasName("Class")));
+  ASSERT_FALSE(ToClassProto->isThisDeclarationADefinition());
+  ASSERT_TRUE(ToClassDef->isThisDeclarationADefinition());
+  // Previous friend decl is not linked to it!
+  ASSERT_FALSE(ToClassDef->getPreviousDecl());
+  ASSERT_EQ(ToClassDef->getMostRecentDecl(), ToClassDef);
+  ASSERT_EQ(ToClassProto->getMostRecentDecl(), ToClassProto);
+
+  auto *FromClassProto = FirstDeclMatcher<ClassTemplateDecl>().match(
+      FromTU, classTemplateDecl(hasName("Class")));
+  auto *FromClassDef = LastDeclMatcher<ClassTemplateDecl>().match(
+      FromTU, classTemplateDecl(hasName("Class")));
+  ASSERT_FALSE(FromClassProto->isThisDeclarationADefinition());
+  ASSERT_TRUE(FromClassDef->isThisDeclarationADefinition());
+  ASSERT_FALSE(FromClassDef->getPreviousDecl());
+  ASSERT_EQ(FromClassDef->getMostRecentDecl(), FromClassDef);
+  ASSERT_EQ(FromClassProto->getMostRecentDecl(), FromClassProto);
+
+  auto *ImportedDef = Import(FromClassDef, Lang_CXX);
+  // At import we should find the definition for 'Class' even if the
+  // prototype (inside 'friend') for it comes first in the AST and is not
+  // linked to the definition.
+  EXPECT_EQ(ImportedDef, ToClassDef);
+}  
+  
 struct LLDBLookupTest : ASTImporterOptionSpecificTestBase {
   LLDBLookupTest() {
     Creator = [](ASTContext &ToContext, FileManager &ToFileManager,
Index: lib/AST/ASTImporter.cpp
===================================================================
--- lib/AST/ASTImporter.cpp
+++ lib/AST/ASTImporter.cpp
@@ -5016,11 +5016,13 @@
         if (IsStructuralMatch(D, FoundTemplate)) {
           ClassTemplateDecl *TemplateWithDef =
               getTemplateDefinition(FoundTemplate);
-          if (D->isThisDeclarationADefinition() && TemplateWithDef) {
+          if (D->isThisDeclarationADefinition() && TemplateWithDef)
             return Importer.MapImported(D, TemplateWithDef);
-          }
-          FoundByLookup = FoundTemplate;
-          break;
+          if (!FoundByLookup)
+            FoundByLookup = FoundTemplate;
+          // Search in all matches because there may be multiple decl chains,
+          // see ASTTests test ImportExistingFriendClassTemplateDef.
+          continue;
         }
       }
 


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