[ASTImporter] Fix unhandled cases in ASTImporterLookupTable

Summary:
In most cases the FriendDecl contains the declaration of the befriended
class as a child node, so it is discovered during the recursive
visitation. However, there are cases when the befriended class is not a
child, thus it must be fetched explicitly from the FriendDecl, and only
then can we add it to the lookup table.
(Note, this does affect only CTU and does not affect LLDB, because we
cannot and do not use the ASTImporterLookupTable in LLDB.)

Reviewers: a_sidorin, a.sidorin, shafik

Subscribers: rnkovacs, dkrupp, Szelethus, gamesh411, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D62064

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@363062 91177308-0d34-0410-b5e6-96231b3b80d8

lib/AST/ASTImporter.cpp

@@ -2256,7 +2256,8 @@ ASTNodeImporter::VisitTypedefNameDecl(TypedefNameDecl *D, bool IsAlias) {
           if (!FromUT->isIncompleteType() && !FoundUT->isIncompleteType())
             return Importer.MapImported(D, FoundTypedef);
         }
-        // FIXME Handle redecl chain.
+        // FIXME Handle redecl chain. When you do that make consistent changes
+        // in ASTImporterLookupTable too.
         break;
       }
 

lib/AST/ASTImporterLookupTable.cpp

@@ -26,17 +26,30 @@ struct Builder : RecursiveASTVisitor<Builder> {
     LT.add(D);
     return true;
   }
+  // In most cases the FriendDecl contains the declaration of the befriended
+  // class as a child node, so it is discovered during the recursive
+  // visitation. However, there are cases when the befriended class is not a
+  // child, thus it must be fetched explicitly from the FriendDecl, and only
+  // then can we add it to the lookup table.
   bool VisitFriendDecl(FriendDecl *D) {
     if (D->getFriendType()) {
       QualType Ty = D->getFriendType()->getType();
-      // FIXME Can this be other than elaborated?
-      QualType NamedTy = cast<ElaboratedType>(Ty)->getNamedType();
-      if (!NamedTy->isDependentType()) {
-        if (const auto *RTy = dyn_cast<RecordType>(NamedTy))
+      if (isa<ElaboratedType>(Ty))
+        Ty = cast<ElaboratedType>(Ty)->getNamedType();
+      // A FriendDecl with a dependent type (e.g. ClassTemplateSpecialization)
+      // always has that decl as child node.
+      // However, there are non-dependent cases which does not have the
+      // type as a child node. We have to dig up that type now.
+      if (!Ty->isDependentType()) {
+        if (const auto *RTy = dyn_cast<RecordType>(Ty))
           LT.add(RTy->getAsCXXRecordDecl());
-        else if (const auto *SpecTy =
-                     dyn_cast<TemplateSpecializationType>(NamedTy)) {
+        else if (const auto *SpecTy = dyn_cast<TemplateSpecializationType>(Ty))
           LT.add(SpecTy->getAsCXXRecordDecl());
+        else if (isa<TypedefType>(Ty)) {
+          // We do not put friend typedefs to the lookup table because
+          // ASTImporter does not organize typedefs into redecl chains.
+        } else {
+          llvm_unreachable("Unhandled type of friend class");
         }
       }
     }

unittests/AST/ASTImporterTest.cpp

@@ -4237,13 +4237,13 @@ TEST_P(ASTImporterLookupTableTest, LookupDeclNamesFromDifferentTUs) {
   ASSERT_EQ(Res.size(), 0u);
 }
 
-static const RecordDecl * getRecordDeclOfFriend(FriendDecl *FD) {
-  QualType Ty = FD->getFriendType()->getType();
-  QualType NamedTy = cast<ElaboratedType>(Ty)->getNamedType();
-  return cast<RecordType>(NamedTy)->getDecl();
+static const RecordDecl *getRecordDeclOfFriend(FriendDecl *FD) {
+  QualType Ty = FD->getFriendType()->getType().getCanonicalType();
+  return cast<RecordType>(Ty)->getDecl();
 }
 
-TEST_P(ASTImporterLookupTableTest, LookupFindsFwdFriendClassDecl) {
+TEST_P(ASTImporterLookupTableTest,
+       LookupFindsFwdFriendClassDeclWithElaboratedType) {
   TranslationUnitDecl *ToTU = getToTuDecl(
       R"(
       class Y { friend class F; };
@@ -4267,6 +4267,52 @@ TEST_P(ASTImporterLookupTableTest, LookupFindsFwdFriendClassDecl) {
   EXPECT_EQ(Res.size(), 0u);
 }
 
+TEST_P(ASTImporterLookupTableTest,
+       LookupFindsFwdFriendClassDeclWithUnelaboratedType) {
+  TranslationUnitDecl *ToTU = getToTuDecl(
+      R"(
+      class F;
+      class Y { friend F; };
+      )",
+      Lang_CXX11);
+
+  // In this case, the CXXRecordDecl is hidden, the FriendDecl is not a parent.
+  // So we must dig up the underlying CXXRecordDecl.
+  ASTImporterLookupTable LT(*ToTU);
+  auto *FriendD = FirstDeclMatcher<FriendDecl>().match(ToTU, friendDecl());
+  const RecordDecl *RD = getRecordDeclOfFriend(FriendD);
+  auto *Y = FirstDeclMatcher<CXXRecordDecl>().match(ToTU, cxxRecordDecl(hasName("Y")));
+
+  DeclarationName Name = RD->getDeclName();
+  auto Res = LT.lookup(ToTU, Name);
+  EXPECT_EQ(Res.size(), 1u);
+  EXPECT_EQ(*Res.begin(), RD);
+
+  Res = LT.lookup(Y, Name);
+  EXPECT_EQ(Res.size(), 0u);
+}
+
+TEST_P(ASTImporterLookupTableTest,
+       LookupFindsFriendClassDeclWithTypeAliasDoesNotAssert) {
+  TranslationUnitDecl *ToTU = getToTuDecl(
+      R"(
+      class F;
+      using alias_of_f = F;
+      class Y { friend alias_of_f; };
+      )",
+      Lang_CXX11);
+
+  // ASTImporterLookupTable constructor handles using declarations correctly,
+  // no assert is expected.
+  ASTImporterLookupTable LT(*ToTU);
+
+  auto *Alias = FirstDeclMatcher<TypeAliasDecl>().match(
+      ToTU, typeAliasDecl(hasName("alias_of_f")));
+  DeclarationName Name = Alias->getDeclName();
+  auto Res = LT.lookup(ToTU, Name);
+  EXPECT_EQ(Res.count(Alias), 1u);
+}
+
 TEST_P(ASTImporterLookupTableTest, LookupFindsFwdFriendClassTemplateDecl) {
   TranslationUnitDecl *ToTU = getToTuDecl(
       R"(